Major atmospheric river event underway; widespread flooding possible

Filed in Uncategorized by on November 29, 2012 132 Comments

Overview

November in California is certainly going to close on a very active note! A very moist and persistent atmospheric river, coupled with two powerful storm systems over the coming weekend, will produce extremely heavy precipitation over a wide swath of Northern California from the Bay Area all the way up to the Oregon border. Flooding is likely in affected areas, initially along small streams tomorrow and then later on the larger rivers by Sunday. Strong winds and thunderstorms will also be possible at times through Sunday afternoon. While rainfall will most likely decrease in intensity next week, a plume of enhanced moisture will continue to stream over the state and produce additional precipitation.

Short Term Discussion

The much-advertised series of increasingly powerful storm systems continues over California at this time. A strong cold front is currently situated across the North Coast region, and is bringing heavy rain, strong winds, and more recently strong thunderstorms to a broad swath of Norcal this evening. Rain from this storm has just reached the Bay Area and will continue to intensify overnight into tomorrow morning. With soils saturated from the quick-hitting but intense rainfall earlier this week, flooding problems will start to crop up overnight on the faster-responding tributaries and in urban areas since the cold front and associated atmospheric river will be slow to move away to the southeast. Winds will not be extremely strong with this storm, but they will potentially be strong enough to start causing minor damage now that soils are completely saturated. Given the recent outbreak of strong thunderstorms along the North Coast and favorable thermodynamic profiles that will persist for much of tomorrow around the Bay Area, I think strong convection is a possibility along and behind the front tomorrow.

Satellite-assimilated precipitable water imagery showing the developing atmospheric river.

The main flooding concern, however, is focused on the Saturday/Sunday system. The models have been very consistent in bringing a very strong and extremely moist storm somewhere into Norcal this weekend and have been generating phenomenal rainfall totals over a broad area (at various points the coarse-resolution GFS has been spitting out aerial averages of 15-20 inches through Sunday). The question has been precisely where the 200-300 mile wide axis of extreme precipitation will set up and cause serious flooding problems. For the past several days, the GFS was targeting the Bay Area with the Saturday/Sunday system; recent runs have shifted the highest precip values slightly north by 50-100 miles into Mendocino County. It’s possible the actual precip maximum could shift another 100 miles in either direction by the time all is said and done; regardless, much of Northern California is slated to receive an amount of rainfall that will certainly cause creeks and streams to overflow and very possibly some of the mainstem rivers as well. I think that event-total precipitation through Sunday afternoon will probably top 20 inches in orographically-favored areas of the Coastal Mountains in Mendocino County and also in the Shasta Drainage region. Snow levels will be quite high through Sunday–generally above 7000 feet–so nearly all of this precipitation will fall as rain and this will contribute to even higher runoff rates than might otherwise occur. And, as with the rest of the systems this week, gusty winds and thunderstorms will once again be possible with the Sunday storm.

Visualization of the evolution of the persistent atmospheric river (NOAA/ESRL).

Long Term Discussion

There is presently some substantial uncertainty regarding the prognosis for next week. The Sunday storm was initially slated to be the last in the series, with a pronounced drying trend helping the state to dry out during the first week in December. The ECMWF model was the first to suggest that the active pattern might continue into next week, and today the GFS started to trend towards the recent ECMWF forecasts. The 18Z GFS actually brought  heavy precipitation back to Norcal by Tuesday, while the most recent 00Z is slightly less bullish. Interestingly, what all the models appear to be keying in on is the continued persistence of our friendly atmospheric river, which by early next week will stretch from just west of the Hawaiian Islands to the coast of Northern California. It’s important to keep in mind that the presence of an atmospheric river does not necessarily mean that extreme precipitation will occur: while the extremely moist atmosphere that characterizes an atmospheric river provides one ingredient necessary for heavy precipitation, a strong synoptic-scale storm system is usually required to generate enough lift to cause significant precipitation (as will occur this weekend). The GFS is not currently indicating the there will be any large-scale storm features to act upon the very moist plume next week, so precipitation forecasts at this time are relatively modest. This is a situation that bears watching, though, since it wouldn’t take much to produce some additional heavy rainfall in the presence of an ongoing atmospheric river event. Stay tuned!

© 2012 WEATHER WEST

 

  • sc100

    Overall, I would say this system is outperforming. Some very impressive rain totals, especially for the North Bay considering what NWS SF was thinking there. They were saying 2 to 4 inches for this storm but some areas have already gotten up to 8 inches. Here are some storm totals since Wednesday when everything began:

    Northwest CA:
    Coffee Ridge – 7.08
    Honeydew – 11.40
    Lakeshore – 8.48
    Clear Creek – 10.32

    Feather River/American River watersheds:
    Bucks Lake – 8.24
    Four Trees – 7.24
    Strawberry Valley – 7.04
    Blue Canyon – 5.67
    Grass Valley – 4.58

    North Bay:
    Ukiah – 4.39
    Yorkville – 7.44
    Venado – 9.64
    Santa Rosa – 4.33

  • Truckee River at Truckee now expected to experience major and possibly destructive flooding on Sunday–perhaps the greatest flows since at least 1955.

    • sc100

      Looks like the worst of the storm for our area right now as the front intensifies and swings through. Could see some very impressive rainfall totals for us over the hours to come.

  • Nicholas

    Here is what we got so far for Whittier, CA

    11/28- Trace
    11/29-0.14
    11/30-0.23

    Try not to get to excited.

    • redlands

      Redlands,Ca Rain Update

      Nov-28 0.00
      Nov-29 0.06
      Nov-30 0.35 as of 751pm
      ———————————
      Total 0.41 —I was suprised we got the 0.35 for today. The totals above are impressive — be nice to get 1/2 of that — even 1/4

  • Shear profiles in the Sacramento valley today look just perfect for supercellular thunderstorms, with forecast sounding depicting perfect curvature, and even a rare loop. Helicity of 100 – 225 M2/S2 will remain over most of the region through the evening. If there is any sunshine, instability and lift could become strong enough for development.

  • Dan the Weatherman

    Light to occasionally moderate rain has been falling here in Orange since late last night, and has been continuing into this morning, but has stopped at the moment, but it looks as it will pickup again shortly.

  • mendodave

    Sunny here in Mendocino, still have a steady south wind at 10mph, baro steady at 29.79″ Total rainfall since the 28th is 3.28″

  • Ken K.

    Surprisingly received some rain at the house today(Granite Hills)
    11/28 0.00
    11/29 Trace
    11/30 .09

    Just enough to make a mess on the roadways today.

  • Tom in San Diego

    Nothing.

  • sc100

    State Flood Operations Chief – Tonight’s storm will be single biggest storm CA has seen in 7 years

    • andy

      Can you point me toward a source for this? I’d like to follow further updates from there. Thanks.

      • sc100

        This came from an interview a KCRA 3 Sacramento reporter did with the Operations Chief. You can read her quote on KCRA’s live wire:

        http://livewire.kcra.com/Event/First_Alert_Weather_November_storm_to_bring_rain_high_winds

        Several local reporters have been at the Flood Center getting quotes from people there. I looked to see if the Center was issuing any press releases but it doesn’t look like it. I guess they’re letting the flood watches and warnings for specific rivers speak for themselves.

        • andy

          Great, thanks!

  • sc100

    Widespread light/moderate rain over my area right now. This constitutes our “break” for today. Sacramento could easily pick up an inch of rain today if this continues throughout the day. I’ve picked up 2.46 inches at my house since Wednesday, .31 inches this morning alone. Areas in the mountains and along the coast have already picked up 2 to 3 inches of rain today with more inches to come before the big storm arrives tonight. We should definitely see 25 inch storm totals from some of these areas, maybe closer to 30. Areas of the North Bay will likely see storm totals of 20 inches, which is incredible for that part of the state. Here’s an update on storm totals since Wednesday up until 9am today. I’ve included areas of the Central CA coast as well, as that area has also seen some impressive rain.

    Northwest CA:
    Coffee Ridge – 7.88
    Honeydew – 13.80
    Lakeshore – 13.36
    Clear Creek – 11.18

    Feather River/American River watersheds:
    Bucks Lake – 12.48
    Four Trees – 10.88
    Strawberry Valley – 11.56
    Blue Canyon – 9.45
    Grass Valley – 6.67

    North Bay:
    Ukiah – 4.75
    Yorkville – 8.76
    Venado – 12.08
    Santa Rosa – 5.48

    Central CA Coast:
    Black Cone – 7.19
    Mining Ridge – 9.74 (since Thursday)
    Three Peaks – 8.41

  • Shady Blues

    Been getting light showers over the past few days. Nothing impressive..its been more of a nuisance than anything. We have yet to see a real frontal down here and it looks like its not going happen anytime soon. What a boring fall and start to winter.

  • 3.58 in. so far here on the SF Peninsula. We’re pretty strongly rain-shadowed by the Coastal Mountains here, so that’s rather impressive.

    The final storm tonight looks like it’s going to produce some major and potentially damaging flooding in parts of NorCal tomorrow. Some mainstem rivers now appear likely to flood after all, including the Napa River, which may actually exceed flood stage significantly. One thing to watch for will be whether any waves form along the front as overhead–this could potentially exacerbate the flooding situation even further if the heavy precip band stalls out even for a couple of hours.

    Everything is still on track for a major event tonight and tomorrow. Stay tuned!

  • sc100

    Looks like rain is going to start filling in over Norcal over the next few hours. I just had a brief convective line go over my house. Really good downpour. I got a rain rate of 1.8 in/hr.

  • Nicholas

    Models just look miserable for So Cal in the long run.

  • sc100

    Things look worse than expected for Sacramento. Incredibly intense line approaching us right now with extreme rain and damaging winds.

    • sc100

      picked up an inch of rain over the last hour

      • Dan the Weatherman

        Wow, that’s impressive for the Sacramento area!

    • sc100

      Also, many areas have storm totals over 20 inches. I’ll have a final list tonight.

  • alan

    Does anyone know if the wunderground temp reading for San Nicholas island is accurate? It shows 82F – I know the islands are quite often the warmest locations for offshore wind events, at least the minimum temps are always the warmest…..

    • Tom in San Diego

      Sounds a bit high, but depends on where the station is. If its on a protected side if a knoll or where it gets direct sunlight, could have some anomalous readings. Normally off shore stations tend to be cooler.

      • Dan the Weatherman

        I have seen a station on San Nicolas Island on the NWS hourly roundups that has reported ridiculously high readings late at night recently and that has been with no Santa Ana winds, so I think it is inaccurate.

        • Dan the Weatherman

          As of the 5:00 p.m. roundup tonight, that station is showing 77 degrees which is impossible with this pattern right now, especially with all other coastal locations in the upper 50s to mid 60s.

          • alan

            That’s what, I thought, thanks guys – it’s always showing up in the “state daily extremes” and was hoping they had sense enough to at least ensure these higher profile reportings remained accurate.

  • Very impressive NCFR moving through Norcal this morning…producing flash flooding in many places. Actual rain rates of 1 inch per 30 minutes and instantaneous rates of 3-5 in/hr have been observed. I observed a rapid inundation of a local stream this morning…exceeded bankful very quickly and actually started transporting large woody debris over the roadway. Impressive!

  • High resolution models nailed the embedded strongly forced semi convective squall line within the mainly stratiform precip.

  • sc100

    I picked up 5.09 inches at my house in Sacramento during this 5-day event, 1.87 inches coming today. The street flooding here today was the craziest I’ve seen since 1995. Basically every street had serious flooding. Some streets looked like rivers. I almost didn’t even make it out of my neighborhood. I finally found an intersection where flooding was shallow enough to make it through with my truck and then I was dodging flooding up and down the streets. Here are some pictures from street flooding sent in by others to KCRA Sacramento:

    http://www.kcra.com/ulocal/Share-your-weather-photos-and-videos-on-u-local/-/11797008/13625088/-/5qmk9r/-/index.html

    Quite a few creeks flooded pretty bad here as well and I’ve heard of some apartments and homes that got flooded.

  • Dan the Weatherman

    It has been a heavy drizzle / light rain event down here in Orange and surrounding areas since mid-afternoon or so. It does appear that a heavier band of rain is between Camarillo and Santa Barbara right now according to radar and Santa Barbara is reporting heavy rain (same NWS roundup that was showing the 77 at San Nicolas Island).

  • Hate to be a downer… but things do look awful for any action after Wednesday, at least for a while. A giant death ridge looks to be present over the eastern Pacific, and to some models it could cover 2/3rds of the northern Pacific by early next week… while the eastern/central U.S. gets into a stormier pattern with troughing digging down from the north.

    • 00z GFS contradicts me with a cold trough next weekend.

  • alan

    Ya so much for my dec 12th storm LOL, it sure was tossing around the idea for a bit though…….. Still an outside chance……

    • Dan the Weatherman

      I feel that we need to get through a series of Santa Ana winds before more significant rain moves into the region. It has just been way too calm in Socal over this past month and it seems that the jet stream has not dropped south into the Great Basin very much to bring the cold air that often leads to the stronger Santa Ana events we usually see between Thanksgiving and New Year’s.

  • sc100

    Here are the final totals for the five-day storm event that started Wednesday. I think some other places got even more than the ones listed here. Overall, a pretty impressive start to the rain season! Sacramento right now is almost 200% of average.

    Northwest CA:
    Coffee Ridge – 11.92
    Honeydew – 20.48
    Lakeshore – 21.40
    Clear Creek – 16.72

    Feather River/American River watersheds:
    Bucks Lake – 19.96
    Four Trees – 19.00
    Strawberry Valley – 18.80
    Blue Canyon – 14.50
    Grass Valley – 11.13

    North Bay:
    Ukiah – 7.99
    Yorkville – 13.20
    Venado – 16.04
    Santa Rosa – 7.85

    Central CA Coast:
    Black Cone – 11.43
    Mining Ridge – 15.74 (since Thursday)
    Three Peaks – 15.81

  • alan

    Haven’t been home to check the bucket – but looks like I will have fallen into the 2″ to 3″ category as I had suspected last week. Rimforest is quite close to me and also faces the valley i.e. along the western/southern ridge – unlike lake arrowhead which doesn’t benefit as much from being the first ridge moisture slams into, and especially big bear city which only recorded .07″

    NYNC1 5516 CABLE CANYON 3.66 NORTH OF DEVORE
    SDRFO 5400 RIMFOREST 2.88
    SDARN 5180 LAKE ARROWHEAD 1.22

    What are some of the highest totals NorCal has recieved from a series of storms like this? Dec 2009 was awesome here for rain, 3 days in a row topped 10″+ for a 6 day rain total of 42″, areas along the western/southern ridge (from crestline to running springs) here recorded 33″ to 44″ for the last week of dec. but geographically it is a small area so it doesn’t grab the medias attention quite like NorCal events.

    • sc100

      That about matches anything I’ve seen from a Norcal storm event. Socal generally has higher rainfall rates than Norcal, both for higher and lower elevations. The 24-hour rainfall record in California is in the San Gabriel Mountains. Norcal has higher yearly totals because it has a lot more days of rain per year.

      • alan

        Thank You for that! Seems hard for me to find info/history for the mountainous areas.

        • alan

          California’s Record Rainfall for a 24-hour period was 26.12 inches occurring January 22-23, 1943, at Hoegees Camp in Los Angeles County

          Wow that’s intense! My highest 24hr rainfall is 14″ and that was part of dec. 09.

  • Tom in San Diego

    60% chance of lt. rain today, but frankly I don’t see it, unless the dynamics greatly improve. We did get a wind shift in the last hour, and pretty good humidity/dewpoint, but with pressure persistently above 30″, and cloud cover well above 5k.and nothing showing on radar, i doubt very much well get much of anything, but we’ll see.

    Temp 56
    Humidity96%
    Wind SpeedE 7 MPH
    Barometer30.18 in (1021.7 mb)
    Dewpoint54°F (12°C)
    Ceiling overcast at 5k, 7 to 8 and broken, 10 scattered, 12 to 20 scattered
    Visibility7.00 nm in haze

  • Nicholas

    Here is what we got so far

    11/28- Trace
    11/29-0.14
    11/30-0.23
    12/1-0.03
    12/2-0.17
    12/3-0.44 (still raining)

    Total 1.01

    • Nicholas

      It could be one of the most unexciting ways of getting an inch or over of rain in a long time.

      • Shady Blues

        I know right? Still impressed that you were able to get that much these storms.

        • Dan the Weatherman

          I will check my gauge later today when the storm is definitely over and report a total. I am curious as to how much fell here as well.

      • makes the plants happy, at least

    • redlands

      Redlands, Ca Update :

      Nov-29 0.06
      Nov-30 0.35
      Dec -1 0.01
      Dec-2 0.07
      Dec-3 0.05
      ———————————–
      Total 0.54 — not very impressive 5 days only 0.54

  • Nicholas

    I will not be reporting rainfall (like any is on the way) because someone at this house broke my rain gauge today and will not fess up to it. I got so mad I smashed it on the ground in hopes that the person who broke it will pick it up as well.

    • inconsiderate roommates suck but the good thing about rain is you can measure it with any cup. If they break the cup too sprinkle the broken glass on their pillow (JUST KIDDING!)

  • Models starting to bring cooler, winter appropriate systems into the area by the middle of the month. 00z ECMWF actually brought in a cold trough next Thursday, while the GFS holds the death ridge in place until the 16th or 17th. The GFS has been pretty consistently indicating a cooler, “troughier” pattern after that.

    • Dan the Weatherman

      BA from tahoeweatherdiscussion.com (he does snowfall forecasts for some ski resorts in the Tahoe region) is saying about the same that you stated above as far as when a stormier weather pattern may return to CA. Dallas Raines (KABC TV – Los Angeles) is also predicting a pattern shift around the 20th that may bring rain back to Socal.

      • Shady Blues

        I have also been hearing that too. In the end, they are just predictions. However, I really hope they are right. If we go into Christmas/New Years without a storm we will be in big trouble!

  • Dan the Weatherman

    1.03″ fell here in Orange from the last several days of heavy drizzle / light rain to occasionally moderate rain, which was much more than I expected. I am glad to see that the area received significant rain to help with the fire danger in case some strong Santa Ana winds come up in the next couple of weeks. I don’t think San Diego County fared nearly as well as Orange County did in this last event, as Orange County was on the southern fringes of this particular storm track.

  • 5.42 inches in total on the lowlands of the southern SF Peninsula–not bad at all for these parts.

    Colder/troughier pattern may indeed be in the works. More later.

  • My gauge (which seems to be over doing it) picked up 7.47″ of rain from Wednesday to Sunday here in Rocklin (about 20 miles E of Sacramento up I-80).

  • sc100

    You can barely even see a rain-snow mix on the radar right now in the Sierra. The snow level has to be over 10,000 feet. Highest I’ve ever seen in December.

  • Tom in San Diego

    I don’t have to check the can to tell you how much South San Diego/Imperial Beach got. Traces don’t count
    YTD is about an inch most of that came in late October.

  • Nicholas

    1.42 since September for my area.

  • Ken K.

    Tom, we did not do so well on the rainfall this time around. Picked up .14 for the total of all storms last week. Looks like a pattern change to cool to cold with the offshore pattern for Sunday to Wednesday Moderate offshore winds with low RH’s, fire danger will be increasing as the rainfall we recieved did nothing to help us out. Hoping for the pattern to change back to rain/snow for the end of the month and for us in the Southland to get some action.

    • Dan the Weatherman

      I feel that we need to get into a colder Santa Ana pattern for a little while before getting wet again because it has been abnormally calm down here this fall so far. It is too bad that San Diego and vicinity didn’t receive more rain with this last series of storms as it appeared that Orange County was on the southern fringes of the more significant rainfall. Of course Norcal was inundated with rain the past few days with the pattern. I think the fire danger here in Orange County and northwestward will be lower for a while, but unfortunately it will be higher down in San Diego where much less rain fell. I hope that no major brush fires break out in any Santa Ana wind this month despite the dryness in some areas.

  • 12z ECMWF looked nice for northern and southern California starting next Wednesday.

    • 00z GFS also now starting to indicate a trough next Wednesday/Thursday… however the 12z ECMWF had reinforcing troughs driving into California for several more days afterwards. Hoping the 00z ECMWF continues it’s previous trend.

      • Dan the Weatherman

        Better model agreement for next Wednesday and Thursday is definitely a step in the right direction. Even the San Diego NWS is beginning to mention the possibility of rain for that time frame.

        • Dan the Weatherman

          A moderate to locally strong Santa Ana event is looking more likely for the Sunday / Monday time frame as an upper low tracks from the Utah / Nevada border Sunday morning into Arizona by Sunday evening. Even though the AFD doesn’t mention it, I am sure that there is a surface high building into the Great Basin behind the low as it is usually the combination of the two features that drives a strong Santa Ana event.

  • alan

    Looks good in the long range – cold and windy in the mountains, oddly humid though, had fog and dew yesterday morning, frost this morning

  • Ken K.

    Fire weather Watch and High Wind watch posted for Sunday to Monday evening, then rain/mountain snow for the latter part of the week with more cold storms behind the first. Classic Santa Ana followed by a storm. Looking a little more promising for us in So. Cal.

  • Looks like a much cooler, unsettled pattern will begin by the middle of next week.

  • Nicholas

    That low on the GFS keeps tracking more and more West with a lot more moisture. It should be interesting to see if that trend continues in 0z.

  • GFS/ECMWF now in decent agreement with the Wednesday/Thursday system… but after that their at each others throats.

  • alan

    Yea NWS already has 100% pops for me wed night, 3 to 7 inches snow and remaining below freezing for 72hrs+

  • Models really don’t want to agree on anything for the weekend… ECMWF has a decent storm, while the GFS keeps us under a weak ridge with over running light precip from the storms impacting the PNW.

  • alan

    Snow total was bumped up to 10″ to 15″ we shall see….

  • sc100

    Regardless of how much rain we get this week, I’m looking forward to the colder weather. We haven’t been below average for a while.

    • Dan the Weatherman

      It has been quite mild this fall down here in Socal as well, and this month has felt more like late October or November, especially with nighttime low temperatures.

  • redlands

    I would have to agree with SC100 — am in Southern California — Redlands — At my station according to my weather records — the maximum average is like 4.22 degrees warmer than the average —- the minimum average is like 6.43 degress warmer —–

  • redlands

    I looked a bit farther — the first 4 days of December 2012 — the minimums were all records according to my records —- its turning out to be a warm December — hopefully it will turn into a colder wetter season — its the time for it — we dont have much time

  • David

    dos any one rember this cold snap way back in 1998

    A COLD SNAP DURING LATE DECEMBER WENT A LONG WAY TOWARD VERIFYING THE COOLER THAN NORMAL LA NINA TEMPERATURE PREDICTIONS. AN ARCTIC AIRMASS PLUNGED SOUTH OUT OF WESTERN CANADA ON SUNDAY…DECEMBER 20TH AND BROUGHT WINTERY WEATHER TO NORTHERN AND CENTRAL CALIFORNIA. FOR THE FIRST TIME SINCE THE WINTER OF 1976…SNOW WAS OBSERVED IN SAN FRANCISCO AND AS FAR SOUTH AS THE MONTEREY PENINSULA. AFTER THE FRONTAL PASSAGE…THE REGION EXPERIENCED A WIDESPREAD HARD FREEZE WITH TEMPERATURES FALLING BELOW FREEZING ON FOUR CONSECUTIVE NIGHTS STARTING ON THE 21ST. ONLY A FEW RECORD LOWS WERE SET DURING THIS COLD SPELL…PRIMARILY BECAUSE IT HAPPENED TO FALL DURING THE SAME PERIOD AS THE BIG FREEZE OF DECEMBER 1990.

    got it from here http://www.sfmuseum.org/hist10/98wx.html

    i think i all so rember that snow fell in most parts of the valley durning that time

    • sc100

      I definitely remember the Dec 1998 cold snap. I followed it pretty closely. I remember it snowing in the valley but it didn’t really stick where I was at. And then the following month Bakersfield got half a foot of snow! I also remember the Dec 1990 cold snap, which was even worse. Plus, it lasted about two weeks. Temps in the valley got down to the mid to upper teens. The Dec 1990 and Dec 1932 cold snaps were the worst in Norcal recorded history.

  • Looks like a nice modestly-cold system this week with attendant low-ish snow levels and isolated thunder, then a potentially active (and cold) pattern redeveloping at some point during the second half of December. Socal finally looks to get in on the action with this upcoming pattern change. Will probably update tomorrow…

    Also, recent model runs are depicting a pretty unusual looking storm system for days 7-8. There appears to be some impressive phasing between a warm subtropical airmass and a cold and dry modified Arctic one off the coast of CA, but there appears to be almost no upper-level support while this occurs (meaning: strong temperature and moisture gradients at low levels, but not aloft). Not quite sure what to make of this…GFS and ECMWF handle it differently, but both put something significant on the charts. Stay tuned…

    • David

      hi Daniel Swain do you rember the CA cold snap of 1998 ?? when the valley mosty got light snow then a vary hard frzzs followed

      • I do recall that there was a very cold (but mostly clear) snap up in the North Bay that year where everything froze solid for a couple of days. We did get a few snow flurries at sea level, but in many ways that event was much less impressive than other, less cold events in the mid-2000s that dumped 6-12 inches of snow in the hills down to around 700 feet AMSL.

        • David

          thanks Daniel

    • 00z ECMWF was very interesting regarding this event. I wasn’t even sure exactly how to explain it. Polar/sub-tropical hybrid I would guess.

      • The 00z GEM also trends much closer to the ECMWF than towards the GFS, but doesn’t dump as much precipitation and isn’t as extreme with the overall setup.

  • Dan the Weatherman

    The Santa Ana wind event that was expected last night and today was a non-event here in Orange, as the wind didn’t even come up at all, despite being under a Wind Advisory. It was warmer today, so the offshore flow did have some influence on the temperatures.

    I am certainly looking forward to the storm for mid-week, and would be nice to get some colder weather for a change with lower snow levels in order to benefit the ski resorts and help with the Sierra snow pack.

  • alan

    It never got very windy here in the mountains either, a couple moderate gusts that’s it

  • Shady Blues

    Interesting GFS runs are getting wetter with the storm….

  • RAP indicates a lot of instability from SFO into the central/southern Sacramento valley/northern San Joaquin valley this afternoon and early evening…

  • Tom in San Diego

    Of course as things develop were getting more realistic guesstimates. This is beginning to look like another outside slider for Socal with most of the energy going to the south and not rounding the corner until late Thursday or, Im thinking, more likely Friday with any rain for San Diego and with Baja getting the wetter side of it, which is great news for us at least.

    • Nicholas

      New model runs take the storm back over So Cal :)/

  • Shady Blues

    Bummer….thunderstorms were removed from the forecast for L.A

    • Shady Blues

      From NWS

  • Shady Blues

    This is one slow front!

    • Tom in San Diego

      Nothings pushing it, you could almost call it a cut off low.

  • Nocturnal convection still ongoing north of Sacramento… pretty odd given the cold sfc temps. Seems to be driven by convergence and some weakly steep mid level lapse rates.

  • I haven’t seen models this optimistic in a long time, even with systems within 48 hours!

    • sc100

      Yeah, it’s pretty cool to see systems out as far as the eye can see, even if they’re not all that big right now. I do think some of these have the potential to get a lot bigger though. The storm track has been very good for us so far this year. Things are looking good for us to have an above normal year.

  • Dan the Weatherman

    It has been raining off and on here in Orange since just before midnight or so. Some of the showers have been moderate at times as well. The showers have been developing off the coast from the south-southwest and moving inland, definitely a favorable flow for coastal areas as the flow is directly onshore.

  • Tom in San Diego

    Leading front just passed over within the hour here. Radar shows a thin red squall line from just below Rosarita to Pt Loma. they usually don’t come ashore that intense, but looks like some good one the way any who.

  • Tom in San Diego

    Coming down pretty hard right now. I’m impressed.

  • Looks like a pretty impressively active period coming up for all of CA, and there is the potential for (initially) some very cold systems and (later) for some rather strong ones. Plan to have an update late tonight…

    • Models pretty different at 00Z, those they still depict a very active pattern. I may wait until the 12z models are in tomorrow before updating to assess the trend…

  • redlands

    Redlands, Ca Weather Update —— Rain for Dec-12 – 0.18 Dec-13 as of 10:16pm 1.68 – for a total of 1.86 — real impressive — really suprised me — i thought Redlands would get only 0.12 to 0.25 tops — on tv news 7 abc — thought we might get nothing —- bring on more rain — with colder temps — be nice to get some snow — Redlands, Ca is due for it — What did others get rainwise ??? Hi 51 low 45.8 as of 10:16pm

    • Shady Blues

      Lucky you!

      I barely managed to get 0.30″ of rain. This storm favored San Diego and the next storm looks to favor San Diego…its not fair…but we have many more storms to come.

  • Dan the Weatherman

    It certainly looks like a more active period coming up during the next week at least. There were some heavier showers here in Orange late last night, easily the most intense of the season so far.

    If this current pattern is a sign of what is to come in the winter months ahead, that would surely be good news for CA, and could certainly exceed at least the lower range of my rainfall forecast this upcoming winter, which was for downtown Los Angeles to receive 4-8″ total for the entire season. L.A.’s total currently stands at 1.43″.

  • I still can’t believe how low model confidence is. Even the ensembles are having some big troubles remaining consistent.

  • Dan the Weatherman

    .61″ fell here in Orange with this last storm, but places south of here into San Diego County picked up quite a bit more. Some impressive San Diego area totals include: 1.97″ at Miramar (just east of La Jolla), 1.56″ at Lindbergh Field (just northwest of downtown San Diego), .92″ at Cabrillo National Monument (at the southern tip of Point Loma), 1.34″ at Encinitas, and .97″ at Carlsbad Airport. It looks as if Las Vegas, Phoenix, and Tucson got in on the act today with some significant rain as well.

    It cleared up enough here in Orange tonight to watch the Geminids and from about 11:30 to 12:30 tonight I saw around 10 meteors or so of varying sizes, two of them being fairly long-lasting and bright.

  • Nicholas

    I don’t like this trend of a parade of weak to moderate storms. Once the parade ends a huge ridge will likely build in and bring 2-4 week dry period. This has even been seen in La Nina years where often December was the most active month and the rest of the winter bombs out.

  • Models still in fundamental disagreement regarding the pattern, but latest GFS ensembles indicate the potential for an extended period of very wet weather for all of CA, right down to the Mexican border. Hopefully a trend will be apparent by tonight, and I’ll have an update soon regardless of the outcome.

  • alan

    Managed to pick up .70″ rain and 15″ snow – switched to all snow by Thursday morning – light snow showers just started again

  • Tom in San Diego

    It did seem to favor us, I got a skosh over an inch less than 4 hours, and a decent shower yesterday afternoon, which i couldn’t measure, since the cat knocked over the tin can I use. (not real high tech here) I imnagine Ken K got that and maybe more since he is higher up the hill than I am and looked like they got a lot of color on the radar up his way.

    San Diego also got some beach flooding at the usual places due to higher tides as well.

    local flight wx info from NOLF Imperial Beach

    Temp 58
    Humidity55%
    Dewpoint42°F (6°C)
    Wind Speed W 12 MPH gusting 15 to 20
    Barometer29.97 in (1014.7 mb)
    Visibility10.00 mi clear
    Ceiling 3 to 4K broken, tops unrestricted

    • Ken K.

      I am sure we did pretty well at home, I am actually in Big Bear with the family until Sunday, arrived up here on Wednesday evening, cold up here, started out as snow Wednesday night, snowing now. Nice change action.,will update my rain at home on Sunday evening. Enjoy the weather.

  • sc100

    The models definitely look like they’re beginning to identify a major weather event starting a week from now. Looking at the full Pacific view, it’s possible it could be another atmospheric river. The next couple days could be huge as the models begin to flesh this out. It also looks a lot more favorable for Socal this time around.

    • sc100

      Looks like I might be right about another AR event. Could be a wild Christmas this year.

    • Yeah–latest ensembles indicate a huge, low latitude longwave trough and a deep associated surface low setting up shop off the CA coast for at least a week straight. Latest GFS runs don’t yet show phenomenal precip totals, but pattern recognition tells me that this potential event for the second half of December has the potential to be very significant indeed, and Socal would definitely get in on the action. Time will tell. I’m not seeing any more extremely cold solutions, though…

  • The models have indeed been awful, they are all over the place. I’m worried the GFS was right over the Euro this time because it means more rain and wintry mix rather than snow in Vermont. But the GFS looked great for beneficial rains to so-cal.

  • sc100

    The models have been wild this week! I’m convinced something big is going to start late next week. I just don’t know what form it’s going to take.

  • yeah, usually when the models bounce all around it means a pattern change is coming in the long term. Just not sure what that is. Out here, there are some indications there could be a heavy arctic blast into New England at the end of the month which would be a shock considering December has been well above average temperatures so far (November was a bit below average). But I hope we’d get some snow before that. Subzero on bare earth is gross.

    It seems every longer term run of the GFS is different for California, but at least I haven’t seen any droughty highs of death lately.

  • It’s snowing up in Redding currently, almost Red Bluff!

    • sc100

      Yeah, that’s pretty cool. It looks like they could see quite a bit of it too. I was just in Redding last month. I’d love to be there when it snows. I wouldn’t want to drive in it up there though!

    • Actually been snowing on the floor of the N. Sac. Valley all day, with some accumulation. It probably also snowed at least briefly in some of the North Bay valleys this AM, since surface temps were at freezing when precip began. Here on the Peninsula…just a lovely 43 degree rain.

  • 12z ECMWF does have another atmospheric river, starting next Thursday, continuing nearly non-stop through the following Tuesday as the large low in the GOA sends shortwave after shortwave into CA traveling along the westerly jet. PW values along the jet look to be around .9 to 1.1″ during duration of it’s event… not as high as the last event, but snow levels look much lower compared to the last atmospheric river event.

  • Shady Blues

    Bunch of weak and pathetic storms….where are the real storms?

    • David

      that’s what you get for takeing 100s of cut off lows last year so paid back time

      • Shady Blues

        Actually they affected San Diego the most…

        • Tom in San Diego

          And Baja even more!

  • sc100

    Boy, next weekend’s system really exploded on the latest GFS. Meanest looking storm of the season so far. Could be very windy as well. This setup still has very big potential, especially since it could continue for most of Christmas week and a clear tropical connection is setting up. By the end of that week Sacramento will probably be close to having as much rain this season as we had all of last season. Last season seems like a distant memory at this point. Looks like you folks in Socal might continue to get hosed though.

    Before all this, we’ll have some pretty cold air here midweek. Really active weather continues here.

    • Mr. ECMWF is not to far off it’s scenario to… can’t wait to see what the 00z ECMWF has to offer compared to that of the 12z run.

  • New blog post! I gave up trying to wait for the models to sort themselves out…

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