Unsettled late spring conditions in NorCal; La Niña Looms

Filed in Uncategorized by on May 19, 2016 2,016 Comments

Cold low to bring showers, thunderstorms, and Sierra snow in NorCal this weekend

A relatively cold late-season low pressure system is currently diving southward along the West Coast after bringing some spring downpours in the Pacific Northwest.

Animated water vapor loop from satellite imagery shows incoming low over Pacific Northwest. (NOAA SSD)

Animated water vapor loop from satellite imagery shows incoming low over Pacific Northwest. (NOAA SSD)

Strong surface pressure gradients associated with this incoming low have already generated strong winds across much of California, including some pretty impressive gusts at San Francisco International Airport.

This cold low will continue to sink southward over the next 48 hours, bringing with it increasingly unsettled weather conditions across the northern half of the state. Showers and thunderstorms will begin tomorrow at higher elevations and possibly spread across the Sacramento Valley by evening. As colder air aloft settles into the region and lapse rates steepen, the atmosphere will continue to destabilize through Saturday. By later Saturday afternoon, showers and thunderstorms may be pretty widespread across Northern California, likely including most of the Central Valley and much of the Bay Area. In fact, some of the same areas that have seen unusually active weather and powerful thunderstorms in recent weeks may see yet more this weekend.

Northern California will be located in a favorable region for convective development this weekend. (NCEP via tropicaltidbits.com)

Northern California will be located in a favorable region for convective development this weekend. (NCEP via tropicaltidbits.com)

Given that the low pressure center will be directly overhead and that the late-May sun angle will allow for strong surface heating during the late afternoon hours, I would not be surprised to see reports of significant localized hail accumulations or even a few severe thunderstorms, especially in the Central Valley on Saturday.

Precipitation will be showery and probably won’t be very heavy in most spots (and will likely avoid Southern California entirely). Some places in the Sierra Nevada and Coastal Ranges could see more significant rainfall totals, however. Late-season snow accumulations are also likely at and above the major passes in the Sierra Nevada, which may cause travel disruptions (especially since some seasonally snow-covered roads have recently been opened for the summer).

Precipitation this weekend will largely be confined to NorCal, with modest amounts overall except heavier totals in mountain areas. (NCEP via tropicaltidbits.com)

Precipitation this weekend will largely be confined to NorCal, with modest amounts overall except heavier totals in mountain areas. (NCEP via tropicaltidbits.com)

 

California’s long-term precipitation deficit lingers, and La Niña looms

While the reservoirs in California’s wetter, more northern reaches have reached (or are nearing) capacity after a slightly wetter-than-average winter in that part of the state, multi-year water deficits remain enormous. The 2015-2016 winter did bring some drought relief to California, but nearly all long-term drought indicators continue to suggest that California remains in a significant drought. Residents of Southern California–who witnessed a much drier than average winter this year despite the occurrence of one of the strongest El Niño events on record–can certainly attest to this. In fact, nearly all of California is still “missing” at least 1 year’s worth of precipitation over the past 4 years, and in Southern California the numbers suggest closer to 2-3 years’ worth of “missing” rain and snow. These numbers, of course, don’t even begin to account for the effect of consecutive years of record-high temperatures, which have dramatically increased evaporation in our already drought-stressed region.

California is still "missing" anywhere from 1 to 3 years' worth of precipitation over the past 4 years. (PRISM)

California is still “missing” anywhere from 1 to 3 years’ worth of precipitation over the past 4 years. (PRISM)

What does the near future hold? Well, it’s probably no surprise to anyone on this blog that California’s long dry season has nearly arrived, and that there’s little chance of meaningful widespread precipitation before next autumn at the earliest. It’s difficult to impossible to be specific about what next winter may hold precipitation-wise. That said, it does appear to be very likely that strong cooling of the equatorial Pacific associated with a developing La Niña event will be a major player. Historically, La Niña has yielded a wide range of outcomes in terms of California precipitation–including both very wet and very dry years. But historical observations and climate model simulations agree that there is a definite tilt toward dry winters during La Niña–especially in Southern California.

The North American Mult-Model Ensemble mean depicts strong equatorial Pacific cooling due to La Nina this winter, but warm conditions remain off of the West Coast of North America. (NCEP)

The North American Mult-Model Ensemble mean depicts strong equatorial Pacific cooling due to La Nina this winter, but warm conditions remain off of the West Coast of North America. (NCEP)

It’s also worth mentioning that the North Pacific is expected to remain very warm this coming winter despite La Niña, and that Arctic sea ice has in recent weeks plummeted to record low levels. At this point, it’s unclear exactly how these striking anomalies might affect California next winter, though this topic is currently forms the basis of considerable, ongoing discussion in the scientific community. Needless to say: another dry winter in California would not be good news, so I’ll be following these conditions closely in the coming months.

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  • alanstorm

    FURNACE WATCH 2016: I had to build a FIRE last night. Cold windy & cloudy in interior Mendocino Co. Got down to 43°. BRRRR.
    Talk about a wild swing in temps. Should be 100° all next week in Ukiah/Lake Co

    • Rainmaker (San Jose)

      may god help us all

      • alanstorm

        100° up my way anytime near July is par for the course. No help from God needed. We are currently at “moderate” fire danger in Mendo Co, last year at this time was “extreme”.
        Next week will be a different story, however. Red flag warnings will be EVERYWHERE

    • Barney

      Pretty sure I’ll be making one tonight as it is starting to snow.

      • alanstorm

        Ya know Barn, its odd were talking of near record cold & near record heat in the same week. 117° in Southern San Joaquin is nuts. Seems like these heatwave pop up so quick. I’m hoping this unseasonally strong cool trough is a sign of things to come this winter.

        • Barney

          Yeah people were complaining about snow falling at the store an hour ago and I quietly laughed to myself for I know that the furnace will be getting cranked to high by Mother Nature within days. I’ll take this cold now, I personally love it.

  • CHeden

    Skies are starting to de-stabilize as the lower levels start to warm. Expecting further development(s) as the aft. progresses.

  • Fairweathercactus

    I have never seen this before.

    One operational note about the heat…the National Weather Service forecast office in

    San Diego has chosen to use a different set of criteria for

    issuing heat related products. It is this reason (not a

    difference in forecast temps) that there is a discontinuity in

    heat advisory/warning on the east side of l.A. County.

    • SoCal Al (El Monte-SGV)

      Yeah, noticed this also. SD NWS has a “heat watch” for those areas and has not issued advisories/warnings like Oxnard. Not sure why they’re not on the same page but the heat wave is still a few days out and they’re probably just being cautious. Also, the AFD does not hint of any monsoonal moisture either.

  • AlTahoe

    The storm is banking up against the crest right now. In my neighborhood the winds must be close to 50mph with an air Temp of 57F. It is cold out.

    • AlTahoe

      Forgot to post the picture

      • Thor

        great shot! Makes me wish I was there 🙂

    • matt (truckee)

      Was just in town and it looked like a winter storm coming in over donner pass. Feels a lot more like March/April than mid-June.

    • Barney

      Second that. As Matt said below feels like a winter storm blowing in. Snow/rain combo here at Donner Lake and extremely windy.

  • craig(Big Sur/Carmel Valley)

    Quite a bit of mtn wave clouds(cap clouds/rotor clouds/lenticulars) just east Sierra crest and NW Nevada mountain ranges today.

  • Thunder98

    Their could be dry thunderstorms pooping up in the mountains and desserts during the intense heat wave which is very concerning.

    • DelMarSD

      The thing is, dry thunderstorms are very rare in Southern California. More often, the problem is too much upper-level moisture, which results in thick high clouds that block convection. Doubt there will be any thunderstorms, just high clouds, which is fine by me.

      • craig(Big Sur/Carmel Valley)

        Up here, central coast area, it usually takes a lifting mechanism, like an upper level disturbance moving up from the south or southeast, to interact with monsoonal and or tropical moisture, to get convection to occur during the summer months.

        • DelMarSD

          The central coast is a whole different thing with dry thunderstorms. Northern California (including the central coast and Sierra) has a much bigger problem with dry thunderstorms than we do.

          • RSmofo

            I only remember one or maybe two dry lightening instances in the last ten years and one was very notable and eerie. 08 or 09 I was driving home from work and lightning was flashing all around me heading up the 330 from work – but for whatever beneficial reason the number of fire starts were all handled no problem – I know the helicopter was out dropping on all of them.

        • Dan the Weatherman

          It usually takes a lifting mechanism such as an easterly wave to produce monsoonal thunderstorms in the coastal and valley areas of Socal. Daytime heating and/or orographic lift are often enough to spark mountain and desert thunderstorms.

      • Fairweathercactus

        When temps get above the usual cap for storms to fire in the beaches and valleys all bets are off. Look what look place in late August of 1998

        • DelMarSD

          What happened in August 1998?

          • Fairweathercactus

            Southern California (mostly Southeast LA County, Orange county) had a monster lightning show that lasted for hours. A funnel cloud touched down as well as well as many locations like mine recorded strong winds with microburst.

          • DelMarSD

            Those weren’t dry thunderstorms, right?

          • Fairweathercactus

            The first day/night it was, the second day cloud shield prevented storms. 3rd day a storm rolled off from the desert and brought a flash flood warning in the afternoon in Whittier. I remember walking home with hail and a strong updraft right before it started raining blew my hat into the sky. It was something out of a movie.

          • DelMarSD

            Awesome.

          • Fairweathercactus

            In that era the weather was fun and had a lot more twist and turns. A far cry from todays “weather” quite sad if you ask an old cactus.

  • craig(Big Sur/Carmel Valley)

    Yeah dry T-Storms could be a concern. The recent GFS shows a monsoon flow pattern developing 5+days out to day 8. But the question is how much moisture will be available over Mexico for this draw? Need to watch that weak disturbance to our ssw, which may ride up the western periphery of the ridge up the CA coast later next week ….depending on how much troughing is off the Pacific NW.

  • alanstorm

    NEWS: ‘Antarctic Carbon Dioxide hits 400 PPM for First Time in 4 Million Years”
    (Sorry, can’t add link)
    No worries, its just a natural cycle?
    Or did it say “4 Million Beers”?

    • Charlie B

      4 million (carved) bears?

      • alanstorm

        That’s what it seems like

    • annette johnson

      Lol about the beer! Sunchaser posted the gizmodo link about the CO2 hitting 400 ppm a day ago if anyone wants to read the whole article.

  • Charlie B

    50 acre brush fire in the Caughlin Ranch area of west Reno. Winds are pretty strong and shifting. This is a very upscale area. Not many trees but lots of sagebrush and dry grass. A fire that started in that general area in 2011 came down into other subdivisions and took out 40-50 houses, and missed ours by 100 yards. 5 others in our development weren’t so lucky and burned to the ground. This one doesn’t look like that kind of animal. The winds are such that it probably won’t burn west or uphill, which is lucky because it’s pretty heavily forested in that area. Fingers crossed.

    • inclinejj

      Can you see the fire from your house?

      • Charlie B

        No. It’s over the hill from me. My wife says she can smell smoke, and the winds are blowing down tree branches in the backyard. It’s a long way from me (3 miles or so). Lots of sirens. It’s now at 100 acres and some homes are without power. Voluntary evacuations.

        • inclinejj

          I always get Caughlin Ranch and ArrowCreek mixed up.

    • alanstorm

      There’s also a fast moving wildfire fire in Calaveris Co by Comanche Lake. Damn winds!

    • rob b-Truckee/East Bay

      Left Reno an hour ago, could see two separate fires in the Coughlin Ranch area, one had flames visible from I80 near Home Depot. Could smell the smoke in downtown Reno and had a few sirens going off just after 1pm when I believe it started.

      The winds were CRAZY, blowing really strong from roughly Robb drive west, lots of dust blowing across the road. Thought I’d see a few fire apparatus along 80 headed from Tahoe/Truckee towards Reno but only saw one vehicle headed East. Although listening to fire dispatch around the Truckee/Tahoe it sounds like Truckee and Cal Fire must have sent their engines earlier. North Tahoe and Cal Fire from the Western Slope seem to covering the area. Crazy part when I got back to Truckee there’s light grapple falling and of course still really strong winds.

  • RSmofo

    I think we are going to have one AMAZING monsoon season with a super duper heatwave to help kick things off – and these 5 raspberry Belgian wheat ales agree!

    • roseland67

      Nice use of the letter p,
      Hate wheat ales

    • Tyler Price (Van Nuys)

      That’s the spirit!! ^_^ we sure will have an epic monsoon season.

      • RSmofo

        What can I say – I get it from you! Along with some fine local microbreweries and, ahem, wild mushrooms… 😀

        And look at that, a day later and NWS is discussing an easterly wave / moisture intrusion after the heat wave peaks….hhmmmm,

  • honzik
    • WarmEpoch4California

      If she becomes a hurricane, she has a better chance. If she stays an “invest”, no.

  • Thunder98

    What the…

    • Thunder98

      LOL! That station is broken.

      • Thirsty Nick (Santa Maria)

        That’s cold.

    • Charlie B

      Yeah but the wind chill is -414.

  • CHeden

    Just now from NWS Sacramento. Been tracking this line for last couple of hours. Got some great lightning video’s (will post one later). Heavy rain is continuing just to my north and west. Looks like a new cell is forming on the southern tip of the convergence line and looks like it go off within the next 1/2 hour or so.
    NOW…
    SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE TO SLOWLY EDGE TOWARD
    THE SOUTHEAST ACROSS INTERIOR PORTIONS OF THE NORTHERN COASTAL
    RANGE MOUNTAINS AND INTO THE NORTHERN AND CENTRAL SACRAMENTO
    VALLEY.

    THROUGH 730 PM…LOOK FOR MOST OF THE ACTIVITY TO AFFECT LOCATIONS
    MAINLY NEAR AND WEST OF REDDING…ANDERSON AND RED BLUFF. LOCALLY
    HEAVY RAIN IS EXPECTED MAINLY NEAR ROSEWOOD…OLINDA AND
    COTTONWOOD.

    IN ADDITION TO LOCAL HEAVY RAIN…PEA TO MARBLE SIZE HAIL MAY
    OCCUR ALONG WITH OCCASIONAL LIGHTNING STRIKES.

  • CHeden

    Looking good on VIS.

  • Barney

    Just took a frigid little hike up on the summit. The wind is howling and it feels like November. Thinking about those thru hikers I met yesterday heading south, I figure they’re around Desolation Wilderness now. Hope they’re bundled up. We’ve had off and on flurries and some light snow all afternoon, nothing serious but nice to look at. I just built a fire but I’ll I’ve got is Oak and it’s burning hot. Probably need to open the windows soon.

    • rob b-Truckee/East Bay

      Light snowfall here for a few minutes, crazy with the heat expected next week. Winds seemed to have calmed down some from earlier.

    • matt (truckee)

      Windy and cold on this side of town (low 40’s now), but not a drop of rain.

    • Charlie B

      Maybe I missed something. PCT thru hikers in this area going SOUTH in June? When did they start? And where? Few go north south because it’s damn near impossible.

      • Barney

        Good catch. Yeah they’re hiking south from Donner Pass to Lone Pine, making up for the whole section due to too much snow. They hit Kennedy Meadows in late May and couldn’t make it over the snow.

  • RandomTreeInSB

    Fire started near Refugio Canyon (west of Goleta) this afternoon, currently 150 acres and growing. Mandatory evacuation has been issued. With the sundowner winds and a heat wave coming up, this is not a good combination. https://twitter.com/KPCC/status/743253553553104896

    • RandomTreeInSB
    • jakobdrafter

      Just got back from watching the smoke plume from More Mesa. Hopefully they got it boxed in with retardant and it can burn itself out towards the ocean.

  • CHeden

    Some excellent lightning west of Cottonwood about 2 hours ago. Some serious rain just our north by Redding is continuing….no totals yet.
    Here’s a quick video of the lightning seen in the still.
    https://youtu.be/HEcD0WNQXiU

    • Pedro

      .78″ at Clear Creek Irrigation District office. 1.0″ here about a quarter mile east. All in about 1.25 hours.

    • SoCalWXwatcher

      I recall Tioga Pass being briefly closed last July 8th because of a freak snow storm. It is kind of weird that we can get an off-season snow in the Sierra, but we can’t seem to buy a decent series of winter storms during January or February.

      • Rainmaker (San Jose)

        wasnt it last year in May 2015 we got a couple cold storms dumping snow which was more then we got November-March. But dont worry our friendly neighborhood RRR will be back in 2017 and there wont be an El nino to save us

      • Barney

        February was horrible but we definitely broke the January curse this year in the Sierra.

    • thebigweasel

      Been raining steadily in the Shasta area for the past 36 hours, expected to continue until early tomorrow. Down here near the foot of San Marcos Pass, very wind and quite cool–51. Enjoying it while it lasts. Temps around 100 Sunday and Monday.

  • DelMarSD

    NWS SD:

    “One of our Facebook fans brought up a great
    question this evening about the potential for excessive humidity to
    sync up during this event. If you look at the medium range placement
    of the center of the monster high across the desert SW by early next
    week, there could be an ideal setup to rotate some subtropical
    moisture around the high into parts of our region. If this happens
    it could bring slightly less hot temperatures, but an influx of
    higher relative humidity air and thus potential impacts from the
    heat index. Something that we would have to fine tune in the
    higher forecast as we get closer to the start of the event.”

    • SoCalWXwatcher

      The humidity would moderate temps somewhat but it wouldn’t feel like it. It would be neat to see some thunderstorms fire up. That would make it all worth it.

  • PrimeMover

    Weather xtremes are happening everywhere. Ski resort in Chile just got pounced with 10 ft. Of snow
    14 June 2016 – In Vostok, temperature of -80.3 degrees was recorded.Coldest since observations began. Meteonovosti.ruhttp://hmn.ru/index.phindex=1&ts=160615112429http://www.ogimet.com/cgi-bin/gsynres?ind=89606&ano=2016&mes=6&day=14&hora=7&min=0&ndays=30Thanks to Martin Siebert for these link

    • Charlie B

      The Vostok report is not accurate. It has been colder there. Records since 1957. It has reached -89.2c. Still this is mighty chilly.

  • Crouching Dallas

    It looks like I’ll be MeltingDallas in a matter of days, so long as the USMNT don’t give me a heart attack in the PNW tomorrow against Ecuador. I might even have to activate the remote office and make for the high country if any of this verifies for Glendale (105+?!) – with a couple of RS’ raspberry wheat ales of course!

  • Thirsty Nick (Santa Maria)

    Sherpa Fire has ballooned to 1100 acres. 5 times bigger than 2 hours ago. Going to be a long week with the heat wave on the horizon. Wind isn’t helping at all.

    • Thunder98

      Dry thunderstorms are a scary potential next week.

    • RandomTreeInSB

      1200 acres now (currently 10a.m.) and 0% containment. Wind calmed down this morning but it’s expected to pick up again this afternoon. That area did not have a wildfire for over 60 years.

  • thebigweasel

    Smoke from Sherpa is visible here, out over the Channel. Everyone’s bracing for a long and very scary heatwave.

  • Apollo

    With the mention of chance of Monsoon moister later next week. The rap around flow, Warm moist air starts from Gulf of Mexico head west then starts to come out of S/SE from the Gulf of California into SoCal. Chances 7 days out. ??? Looks like a good setup.

    • Thunder98

      Can’t wait!

    • CHeden

      Careful what you wish for. I’d be concerned about dry T’storms if they do develop.

  • CHeden

    HRRR is forecasting widespread showers in the North SacValley around 4-7 p.m.
    A small complex is currently coming ashore between the North Bay and Pt. Arena. As this wave moves inland during the day, the main GoA circulation center will be offshore Ca/Ore border. The flow around this circulation will help steer moisture from the wave northward up the gut of the Valley during the aft. bringing another chance for convection to the area…. all depends on how many breaks we get in the cloud cover to help de-stabilize things. As expected, the rain totals from yesterday were highly variable due to the training of rains within a narrow convergence zone over the far west valley. To illustrate, Redding Apt. got 1.1″ with over 3 hrs. of precip while my house a mere 11 miles south got ziltch. Even within Redding, rain totals were highly variable with far-east Redding getting only 0.36″ and Whiskeytown less than a tenth. This morning, skies are broken Cu with a layer of stratus above with a mean flow from the ESE aloft with strengthening S winds at the surface…decidedly more unstable looking than yesterday at this time. Hopefully more action for today?

    • inclinejj

      CH

      If you get a chance to come back down to Pacifica area you have to stop and check out the whales. They have been putting on a show the last couple weeks. Last week they were 20-40 yards off the end of the pier.

      • CHeden

        Will be down next week, and was planning to hit the beaches for some striper action (reports are so-so, I heard). Last year, the whales put on a show every time I came down throughout Spring through Fall. Most I’ve ever seen in 45+ years. Glad they’re still here.

  • inclinejj

    Every time it starts to drizzle or mist. It goes away..poof. The deck was a tad wet early this am..Pacifica (5 am)

    • alanstorm

      Well, this storm was a TOTAL FLOP, put out tarps & rolled up car windows for nothing.
      Chan 7 weather dude has major egg on his face from last night’s forecast of “could be rainiest June day on record tomorrow” then showed silly model of yellows slamming the North Bay at 5am.
      -sigh-

  • Apollo

    Thought I’d share a task I’ve taken on. Welcome to a buetiful and cruel world my little friend.

    • Dan the Weatherman

      Did you have some milkweed growing nearby for the caterpillar to feed on?

      • Apollo

        Yes, what I do is grab the caterpillar of milkweed when it comes out of its second instar and the I put them into a screen encloser for safety. Safety from mainly predators which there are a lot of. Monarch caterpillar have maybe a 10% (10% from 100 of eggs) chance of survival from egg to butterfly. Besides the environment no longer being in there favor for migration. I’ve at least gave them a 50%+ chance to survive being in the encloser until there butterfly’s.

  • alanstorm

    Can’t recall seeing a forecast of 11 days straight of 100°+ for Sacramento in quite awhile. For places like Red Bluff & Fresno, its 11 days of 105°+.?

    • And, if GFS is right, you that might STILL be an underestimate.

      • alanstorm

        GFS- Gonna Fry Soon

        • Brian

          I love blistering heat waves. The best of times are coming.

          • Dan the Weatherman

            Maybe it will lead to a monsoonal outbreak at some point. Hot weather patterns like this can lead to thunderstorm patterns if the setup is favorable.

          • annette johnson

            Personally I am looking forward to it. It looks like the brunt of it will be over Lake Havasu. Our temps have been way to mild (low 100’s)to usher in any hope for storms. Ya, it will be $#&#ing hot, but bring it-Im ready.

      • Brian

        It’s an underestimate….

    • Still planning on a full blog post later today.

    • Brian

      YUP!!

    • Dan the Weatherman

      I am assuming that is more for the far inland and desert areas as opposed to coastal and inland coastal regions. For the coastal and inland coastal locations of Socal, Monday appears to be the hottest day with gradual cooling as the week progresses even if temperatures are still somewhat above normal.

  • Thunder98

    Weather.com is way underestimaing the temperatures compared to the NWS.

    Weather.com
    Monday: 85F
    Tuesday: 87F

    NWS
    Monday: 97F
    Tuesday: 94F

    • Apollo

      Same forecasted for my town with a 8 to 10 degrees different from the two.

    • 82/83 El Nino Baby

      I think NWS pulls more local readings whereas TWC uses the standard airport reading. In San Jose, TWC is always a good 10 degrees lower than where I live.

  • CHeden

    Not sure, but it looks like a hint of a baroclinic leaf may be setting up SW of Red Bluff and should be lifting NE into the valley during max heating. Skies up here in Cottonwood are crystal clear visibility-wise (indicating good vertical mixing), with scattered fair weather Cu. Temp is up to 75F….a full 10 deg warmer than yesterday at this same time….so all in all, the setup certainly seems favorable for some convection to start firing up in the next few hours.

  • CHeden

    Quick sky check is showing a zone of rapid destabilization SSW of Cottonwood, and appears to moving this way. Winds aloft now have a slight SSW component which is also a favorable direction for pushing storms into the valley. As was the case yesterday, the most unstable zone appears to west of I-5 (ATTM), but not expecting it to stall like yesterday given the slightly different wind direction.

  • Apollo

    I not down playing the up and coming heat wave it’s going to be HOT. But what’s forecasted and records to be broken are only looking to be 3 to 5 degrees above to due so. Any places to see a 10 to 15 degrees above record(s)?

  • #1 prophotorgb #2 normal