Strong atmospheric river likely to bring widespread, perhaps severe flooding to Northern California on Monday

Filed in Uncategorized by on February 19, 2017 8,491 Comments

Potentially dangerous flood event this week across wide swath of Northern California

Models are suggesting a high likelihood that the slow-moving atmospheric river will stall somewhere near the Interstate 80 corridor on Monday.. (NCEP via tropicaltidbits.com)

On the heels of a strong, damaging, and deadly Southern California storm on Friday, a new and powerful storm is bearing down upon Northern California. A deepening low pressure system just off the California coast will drag an extremely moist plume of subtropical moisture over the northern half of the state, bringing a prolonged period of moderate to heavy precipitation with high snow levels over a 36 hour period from late Sunday to early Tuesday. This brief update will focus exclusively on the major flood risk posed by this weather setup given extremely wet antecedent conditions.

 

Slow-moving atmospheric river may stall near Bay Area, Sacramento regions

The atmospheric river associated with the Monday storm will be very impressive in its own right–the amount of atmospheric water vapor transport near the Interstate 80 corridor on Monday will be of a magnitude historically only seen every ten years or so in February. Even more problematic than the overall amount of moisture is that the atmospheric river boundary itself is expected to be very slow moving, and may in fact stall across some portion of Northern California.

Yet another well-defined atmospheric river will make landfall across Northern California. (NCEP via UCSD)

As the offshore low lifts northeastward, the moist plume associated with the warm front will make slow progress northward during the day on Monday before reversing direction and moving more rapidly southeastward as the cold front approaches. The I-80 corridor (including the Bay Area and Sacramento regions) will be near the classic “triple point” of the warm, cold, and occluded fronts–which is a recipe for major flooding, since the atmospheric river can effectively “pivot” over a relatively narrow region. It’s still hard to pinpoint exactly which region will be most severely impacted, but I expect some serious flooding later Monday in a relatively narrow region somewhere within about 100 miles of the I-80 corridor. Even outside of this band of potentially dangerous rainfall accumulation, widespread heavy precipitation will still occur and lead to considerable flooding, mudslides, and other issues.

While the warm and wet precipitation will slowly taper off on Tuesday, it now appears that an active pattern will continue thereafter (albeit a much colder one). Additional precipitation accumulations may add to already considerable flooding later in the week, although at least snow levels should be drastically lower by Wednesday, reducing overall runoff.

 

Widespread flooding likely; severe stresses on California’s water infrastructure

Integrated water vapor fluxes over Northern California will reach values rarely seen during the Monday storm. (NCEP)

California is currently in the midst of one of its wettest winters on record, and precipitation since January 1st has already led to widespread water-related impacts. Widespread inundation of agricultural lands is occurring, which has begun to spread into low-lying nearby communities in the Central Valley; innumerably many mudslides and landslides have been occurring almost continuously in Northern California, causing numerous roadway failures and affecting some heavily traveled routes; and most of California’s major and minor reservoirs are now nearing capacity, requiring large water releases. All of this water is severely taxing California’s water storage, conveyance, and flood protection systems. With the major exception of the Oroville Dam spillway crisis–a situation that appears to have stabilized for the moment–no major failures have yet occurred elsewhere.

But given the magnitude of the incoming Monday storm and the precariousness of the present situation, it’s becoming increasingly likely that problems will arise this week. As others have pointed out, the present situation is very similar to those which have historically resulted in major levee failures in the Central Valley and Delta regions. Undoubtedly, this week’s weather will be a serious stress test for California’s aging water infrastructure. Indeed, the potential exists this week for severe flood-related impacts of a magnitude not seen in many years. This is a storm to take seriously!

I’ll be following this high-impact storm and its impacts in real time on Twitter.

 

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  • Nathan

    Video of reopening the Oroville gates today:

    • Yolo Hoe

      That’s cool — aside from the profound comments regarding ‘aging infrastructure around the world’ and the repair designs that may shrink the reservoir’s capacity going forward, and the awesome video footage, I loved the brief description at the end of his ‘mobile reporting unit’ — thanks for posting!

      • norcal

        The shutting down of the Hyatt PP is normal during heavy spillway use. The increased water level in the Tail race is normal during flows that exceed 35,000 cfs. The Hyatt can only be operated when the flows are below that number. So the shutting down of the Hyatt is not abnormal. There will be some moving around of debris, and another round of dredging, but that is to be expected.
        What is concerning is the potential for scour at the spillway gates…………

        • DelMarSD

          Hyatt… LoL, I thought you were talking about the hotel for a moment.

          • Pfirman

            The tie in is a lot of people had to stay somewhere besides home for a couple days during the evacuation.

        • Pfirman

          I’m not at all clear about what exacerbates scour and what prevents it at this point, with so many other concerns.

          • ben

            As the lake level drops, the water flowing to the main spillway gates gets shallower thereby increasing its velocity on its approach to the gates. The channel the water flows through to reach the gates is unlined, and appears to be highly weathered in places, making it susceptible to erosion. But DWR doesnt want flows below 40k cfs due to increased erosion directly below the end of the undamaged spillway during low flows that dont launch the water out. Over 50k cfs, excess erosion below the damaged spillway will rebuild the debris delta in the recently cleared channel. Its precarious because if the main gates get damaged… Its only 15k cfs out power plant until e spillway spills excess, if they even can get the hyatt on full flow quick enough.

          • Pfirman

            Unlined? Whoa. Seems like a terrible oversight. I get the reason for the 40K as a delicate balancing point, just did not understand reason for scour. Unlined, yikes.
            And thanks.

          • ben
    • CHeden

      Thank you for passing this on. Great amount of info and the video was excellent in support to the dialogue.

  • CHeden

    With Daniel’s new post on the way, thought I’d just provide a quick update on next week’s NorCal weather.
    The pattern has evolved pretty much as expected since my last update several days ago., and therefore my confidence is rather high is what we can/should expect.
    Currently, our “sacrificial lamb” storm is tracking SW-NE off the NW coast, with both the low to the north and west coast ridging both starting to weaken. Up here in Cottonwood, we’ve received a few light showers, and there is even a chance of some showers this afternoon during peak heating hours before things dry out for the remainder of the weekend.
    As low pulls away and moves into the upper Great Basin tonight, a brief period of drying will set in as a weak ridge gets pulled north by the departing low, then get’s replaced by a digging trough in the Mon/Tues timeframe as the storm door opens wide. The main question was/has been where this next upstream low would track and whether the generic pattern would become more progressive. At this time, it looks like the low will track to near the NW Cal/Ore coast and in turn push a quite dynamic cold front through the area around Tuesday. This CF will usher in some colder air as the mean trough edges over the west, and in turn scattered showers with some isolated convection will hang around until at least Thursday…or at least until the next upstream low starts to track towards the coast and pushes the downstream low/trough eastward. This new low will be much more dynamic than the previous two, with a better sub-tropical moisture tap and more cold air to work with. By the 24th-25th, most of California will get some possibly significant rainfall and possibly high winds (especially along the coast and over the ridges), with the northern/cent Sierra and southern Cascades getting perhaps as much as 4-5′ of new snow above 6,500-7K’, with lower snow levels and totals coming down to around 4K’ by next weekend. This low will also track more progressively W-E, so we should be seeing some decent Pacific forcing to help keep the CF chugging along as well as increasing the overall post-frontal instability.
    As for hydro issues, I am particularly concerned that the Oroville drainage area may see 5-8″ of liquid between these two storms alone next week, with more storms lined up for the following week. All told, the GFS is suggesting upwards of a foot of liquid may fall between now and 384 hrs in the northern Sierra/Feather River area and Lake Shasta area, and that doesn’t take into account snow melt below around 6K’…..so no wonder the DWR is releasing so much water beforehand. Should any convective cells develop (which I expect both around Wednesday and again next weekend) then stall out (as they sometimes do this time of year), there would also be a threat of flash flooding and/or large amplitude spikes in local river/creek flows that happen to be directly under the heavier rainfall.
    Really looking forward to Daniel’s take later today before re-visiting my current thinking.

    • Nice update! Oroville needs to keep a 750,000 acre feet of flood pool until a certain period in spring. There’s going to be a lot of runoff and IMO they will have a pretty good flow out of the gates and keep them open. Spillway gates open allows the reservoir to get below flood pool. So I expect a good flow to get them down. The spillway was designed to release up to 150,000 cfs @ 835 feet according to original construction and design info.

      • CHeden

        Have you heard (read) what max flow the damaged spillway can handle? If I remember, at the time of 100,000 cf/s flow rates, the damage to the spillway was extensive at first, then seemed to not get much worse once the main “chute” got carved out to the right of the ramp?

        • I haven’t . Most released through gates has been ~115K CFS right around the 1996-1997 event. Total release that time was 129K CFS and I’m assuming the hydro plant was releasing and there were/are to other deep release pipes that haven’t been used since a 2009 accident.

          • norcal

            In 1997 the total release was 160,000 cfs. All of that came from the Spillway. The gates can actually release around 260,000 cfs. At that amount the damage downstream would be catastrophic. The levee system in Oroville is good to about 150,000 but there would be issues. The west levee from the Afterbay to Yuba City is good to about 200-210,000 cfs.
            When the lake level is at or near 900 max flow can be achieved, as the lake level lowers, the head pressure reduces and the total natural outflow through the gates is reduced. They are only legally allowed to release 160,000. Even at 150,000 there are profound effects downstream.
            The spillway did perform well considering its condition at 100,000. It did tear itself apart, but the head cutting was minimal. The river valves have not ever been used since they were shut when the dam was filled. The attempt to start them up was when the problem occurred. They have been re-built- but total flow through the river valves is around 4000 cfs. The only real way to maintain flood space is through the normal spillway. Any significant inflows will cause a lot of issues…..

          • Pfirman

            Croyle early on did mention a ‘fish valve’ that he ‘hoped’ would work as expected since it had been upgraded recently and had a flow of around 4000-5000. Its use was intended to supply cold water for the fishery downstream. It remains unclear to me if it has been used or is planned to be used.

          • That number may be more anecdotal. The records from CDEC show a lower spillway release.

            It’s not designed for over 150K CFS but can handle more up to the point the water is at the spillway drains about 20feet from the spillway bed. The 260K CFS is calculated with gates open AND a freeboard of 5 feet on the weir. YIKES! Yes there is a release limit. I was referring to the design and specs of the headworks. It ‘can’ release 150k at 835 feet would it ever be done? No

    • Craig Matthews

      Such top notch description here, thanks! Lots happening on the NPac playing field… just need to move that endzone down to Socal.

  • Boromir (Orcutt, CA)

    Its so foggy this morning!

    • DelMarSD

      Same here.

  • Boromir (Orcutt, CA)

    April and October are transitional months from the wet season to the dry season and vice versa in Central and Southern California.

    • That’s keeps gettin’ better. Hope GFS holds steady T2 anomalies aren’t bad either. Hope it’s fluffy

      • PRCountyNative

        MMMmmm flufffy!

  • thebigweasel

    Those of us who can’t attend will be cheering you on at March for Science, Daniel!

  • Stereolab
  • CHeden

    Same thing as Steoreolab just passed on, but with precip scaling.
    This may be the most bullish run yet from the GFS. Really hoping this becomes an outlier. These monster totals could really wreak havoc…especially if the snow levels stay high.

    https://uploads.disquscdn.com/images/78f3164db74da6c73090dd9c10d4c4977b96338240aa645e42d4156ee090d8ae.png

    • Craig Matthews

      Not a good sign for Oroville dam situation, and all the hydro related issues elsewhere across the North State. Do you or anyone know if GFS is still producing the wettest scenarios compared to ECMWF and CMC?

    • Whoa!

    • Thunderstorm

      This is the last thing I’d want to see if I lived below the Oroville dam. The upper part of the spillway sits on the red rock. You know what that means. Likely the same material in front of the emergency spillway is also used under the chute of the permanent spillway.

      • Nathan

        Most of these storms are pretty spaced out. I’d only anticipate a problem if it was this volume of water in 1-2 storms in a row, which is what we got in Jan and Feb. Also not likely to verify. I think they have a good handle on things.

        • ben

          Id feel better if they had continued concreting directly below the e spillway an extra hundred meters or two northwards.

  • Fred Garvin
    • Nathan

      Garbage

  • Fred Garvin
    • Nathan

      Trash

  • Fred Garvin
  • Fred Garvin
    • Nathan

      Embarrassing

      • Fred Garvin

        Yes you are, wake up to reality. The biosphere is imploding and you choose to stay asleep.

  • Fred Garvin
  • Fred Garvin

    Pilots, Doctors & Scientists Tell Truth about Geoengineering

  • Fred Garvin

    Undeniable Footage Of Jet Aircraft Spraying (GeoengineeringWatch.org)

  • Fred Garvin

    CIA Whistleblower Speaks Out About Climate Engineering

  • Fred Garvin

    Geoengineering Whistleblower ~ Ex-Military USAF ~ Kristen Meghan, Hauppauge, NY, January 18th, 2014

  • Fred Garvin

    Former FBI Chief Ted Gunderson Says Chemtrail Death Dumps Must Be Stopped

  • Jason
    • Pfirman

      Change in the weather too. Where did you take that shot from and what direction are you facing? Looks like west. I think I can see the Berryessa Gap off in the distance.

    • Jason

      I’m on Amtrak looking north right next to West Sacramento.

  • Fred Garvin

    What Chemtrails Are Doing To Your Brain – Neurosurgeon Dr. Russell Blaylock Reveals Shocking Facts.

  • mattzweck

    here in the high desert /Lancaster area nice and spring like about 76f out a little breezy.

  • Fred Garvin

    Rosalind Peterson, former USDA, addresses UN about Geongineering

  • Full update still in the works for later today…should keep the comments section below 8000. 🙂

    • Pfirman

      Cool, and we can leave the chemtrail troll behind in the mysts of thyme.

      • Yolo Hoe

        Or preferably missed time next time.

    • Better be soon. Was nearly 7900 a few minutes ago! 🙂

    • thebigweasel

      Of course, it’s around 8,400 if you include the “where is northern California” thread that was deleted…

  • For those interested, here is a “Climate Feedback” review of the scientific credibility of the Great Barrier Reef NYT article some people were discussing earlier (the verdict: high to very high credibility).

    I do participate in the Climate Feedback review process when the topic is a bit closer to my own knowledge.
    http://climatefeedback.org/evaluation/great-barrier-reef-coral-climate-change-dieoff-the-new-york-times-damien-cave-justin-gillis/

    • Nathan

      Thanks for sharing. When climatefeedback publishes a similar review using the data collected in November 2016 and compares it to that collected in March 2016, please share that too!

  • inclinejj

    Noticing something weird. My Humidity is bouncing around all morning. From 23 percent to 29 percent. Someone said the other day he had 10 percent humidity? Pacifica.

    • There’s a spittle bug living inside your sensor.

  • I have about a 20-30k photo backlog from the past few months at Donner Summit, recent shot of some clouds up there – no digital trickery, just underexposed so I could catch the iridescent moisture.
    http://i.imgur.com/pTXs9cv.jpg
    Snow Crystals on Covered Wagon at 9,565 feet. Way underexposed 🙂
    http://i.imgur.com/36Of9ma.jpg

  • Long Range Views:
    Southern Coast Ranges from Donner Summit:
    http://i.imgur.com/FJe0l8j.jpg
    Mt Diablo from atop Covered Wagon 9,565 feet:
    http://i.imgur.com/TqgHhnw.jpg

  • Craig Matthews

    Here’s a quick comparo of 500mb geopotential heights between this winter and last(from Dec 1 to Mar 16)….This winter looks like it had a La Nina-like pattern in the NPac ( Ridge in the higher latitudes of the central NPac, trough along PNW, and sub tropical ridge stretched from SWUS toward the NE). And there’s last winter’s https://uploads.disquscdn.com/images/b57607c329fb36a2eea5c4dcf0cbd7858f4ed8d134d498838bc50c8fbad91e1e.gif https://uploads.disquscdn.com/images/b0da8b68120b6b0706f8cb5e5b0b0808058421f9fbc1dce64323c03e7d9ccf2a.png

    • Yolo Hoe

      Very interesting comparison — thanks for that. Any thoughts on key drivers of these two patterns given the peculiarities of this year and last?

  • Craig Matthews

    American Meteorological Society President, Matthew Parker, has passed on. He will be greatly missed. https://uploads.disquscdn.com/images/73f093ef65b060c892c10257101d03de2ca1ea7e064441c928e08667b0945f38.jpg

    • Chatman

      RIP Mr. Parker

    • Charlie B

      He was 53. Egad. Of course, the measure of someone is not how long but rather what is accomplished during the time you have here.

  • ben

    Far norcal just got blasted, half inch in past 3 hrs at ACV airport

  • Leah Weiss (Olympic Valley)

    Friday morning view from the top of Tahoe Park Heights Dr. (near Sunnyside) shortly before sunrise. Heavenly is on the left. https://uploads.disquscdn.com/images/116b540bf8caec4e0fe1c0ae405baedb960776ab2e59a7e8b47db42c8f6c39ce.jpg

    • Yolo Hoe

      Nice pic — great time of day on days like this

  • Tyler Price (Monterey/Seaside)

    Wow the most recent model runs are really looking good for a full return of wet weather and stominess for the entire state!! We will all get plenty of rain with convective showers and T-storms in between solid rainmakers! Even the ECMWF is getting fully on board and still showing numberous storm’s statewide.. it’s gonna be a fun way to wrap up march! This is going to be one hella of a storm parade starting next week! Cheers! ?????????

    • Bartshe

      except for 18z which has cut total precip roughly in half through 216 hrs

      • jstrahl

        The 18Z did this on Thursday and again yesterday. May something wrong with the 18Z shift?:-)

      • Geomagnetic Storm must be having fits.

      • Tyler Price (Monterey/Seaside)

        It’s an outlier for the LR those storm’s will
        Come back watch

    • Bobby M ( San Carlos/Tahoe)

      Those Tstorms better show up, maybe even surprise us with some strong ones

  • alanstorm

    GFS was spot-on 2 weeks out for decent weather for the Dublin St Patrick’s Festival when everyone told me it would rain.
    Glad I believed.
    So now I will cancel my booth at the Good Guys Car Show next weekend because of the STORM.
    https://uploads.disquscdn.com/images/d4fb6ce45e61d2372f71fe50b96d9ecb3c76b1c0e32751862e3b1bb45eef5cd5.jpg

    • Weather looks terrible. Are the crowds good?

      • alanstorm

        Terrible blue sky!
        Yes, tons of peeps. Porta potties already full?

    • Yolo Hoe

      Looking forward to catching one of your shows — nice call on the weather

      • alanstorm

        Last year they said they had to evacuate people out of here because of flooding! (Dublin Civic Center)

    • Pfirman

      The Golden Bear! Go Cal!
      Could be Cal Worthington and his dog Spot.

  • Admode (Susanville)
    • Rio Rat

      Sunshine on dark thunderheads are always one of my favorite weather looks.

  • janky

    Light rain in Truckee

  • ben

    .27″ past hour, 1.06 for past 6 hr. If its this wet here, the origraphically favorable areas must be torrential!

    • CHeden

      Location?

      • ben

        Humboldt county airport, elevation 222′

        • CHeden

          Thanks!

        • Pfirman

          Safely above tsunami threats.

          • ben

            My house sits on an active fault though ….

          • Pfirman

            In California, you are not alone.

  • CHeden

    During the afternoon, a wave within the base of a digging trough now out around -135E, 32N seems to be showing signs of closing off. The models up to this point were showing this feature remaining as an open wave, but this WV seems to be showing otherwise.
    ATTM, there does appear to be some lift in the immediate area of lower pressure, but mostly just high cloudiness is streaming out from the core. Once the low rounds the base of the trough, it’s likely to track to the NE, bringing it over Cent. Calif. on Sunday. Not expecting anything widespread, but at least there’s a decent chance of some light precip or even a cell or two popping up should any residual circulation (and ascent) move overhead.
    https://uploads.disquscdn.com/images/45654f1ab9c5bd58930e3135109000598e24ae43e7301394809d98c1d484e6fe.jpg

  • DelMarSD

    Recent model runs show San Diego getting over an inch on Tuesday/Wednesday. That would be great. Still lots of uncertainty, but the potential is there for greater amounts, since there will be a strong subtropical tap. Will be interesting to keep an eye on this in future model runs. Especially the 2nd shortwave on Wednesday, as recent runs have been trending wetter with this.