Extraordinary winter warmth and dryness to persist as West Coast ridge dominates

Filed in Uncategorized by on February 1, 2018 5,156 Comments

Summer in January; Sierra Nevada snowpack nears record low

Well below average precipitation has been widespread so far this winter across most of the American West. (WRCC).

Remarkably warm conditions have persisted for most of the winter thus far across the entire American West, except for the far Northern Rockies. (WRCC)

Despite the calendar, it sure hasn’t felt much like the middle of winter across California in recent days. While well above average temperatures and below average precipitation have been widespread throughout the state, recent warmth and dryness have been especially concentrated across Southern California. Immediately following the warmest autumn (and before that, warmest summer) on record, a legitimate mid-winter heatwave baked the southern third of the state this week, setting numerous high temperature records. In fact, anomalous offshore flow brought daytime temperatures near 90 degrees and overnight lows above 70 degrees near the Pacific coastline–temperatures that would be well above average in these areas in June, let alone January.

While temperatures in SoCal have now moderated somewhat, they’re still quite mild for this time of year (running a “cool” 10-15+ degrees above average).

Snowpack is at or near record low levels across much of the American Southwest this February.

Additionally, this highly anomalous warmth has now spread northward across the rest of the state–bringing spring-like temperatures to the Sierra Nevada and inducing unusual mid-winter snowmelt. The statewide snowpack has already been tracking near record-low levels for most of the winter (partly due to modestly below average precipitation but mostly due to far above average temperatures), but the ongoing warm and dry spell will likely melt what little snow currently exists below about 8000 feet in elevation. The lack of snow in California so far this winter is actually part of a much broader “snow drought” that currently extends across most of the mountainous interior of the American West, from the Cascades in Oregon to the Front Range of the Rockies in Colorado. Much as in the Sierra Nevada, these largely snow-less conditions are the product of both below average precipitation and above average temperatures across a wide swath of the Southwest so far this season.


“Severe drought” has returned to parts of Southern California

Today’s update of the U.S. Drought Monitor suggests that “severe drought” conditions have returned to parts of Southern California–most notably, Santa Barbara and Ventura Counties, where huge tracts of land have recently been burned by the nearly 300,000 acre Thomas Fire (in December) and/or the localized but devastating debris flows and flash floods (in early January). That might not come as a surprise to local residents–many of whom will point out that California’s multi-year, statewide 2012-2016 drought never really ended locally (where Lake Casitas, the only source of water for several communities, is running at about 35% of capacity). While the Northern California reservoirs are generally in much better shape due to carry-over from last year’s deluge (and California’s big cities, which are all tied into the state water system, are therefore unlikely to experience water restrictions this year), California’s wildlands and ecosystems will most likely experience more immediate adverse impacts from yet another warm, dry winter. The recent drought was a major factor in the bark beetle-linked mortality of well over 100 million Sierra Nevada trees in recent years. Despite last year’s wet and cooler reprieve, these drought and beetle-stressed forests have yet to recover from the intense multi-year drought that preceded it–so there is serious concern that forest mortality could accelerate once again during the upcoming dry season.

Los Angeles has experienced only a single day of precipitation greater than 0.33 inches in nearly 365 days. (NOAA)

Just how dry has it been in Southern California? As a current resident of Los Angeles, I found the following statistic especially striking: if the city reaches February 19th, 2018 without a significant rain event (as currently appears plausible), there will have been only a single day with more than a third (0.33) of an inch of precipitation in the preceding 365 days–a full calendar year.


A big West Coast ridge has returned…and it looks pretty resilient

GEFS and ECMWF ensembles both strongly suggest persistent ridge will keep West Coast dry for 2+ weeks. (NCEP via tropicaltidbits.com)

At risk of sounding like a broken record: a strong, persistent, broad, and anomalous ridge of atmospheric high pressure has yet again set up along the West Coast. All indications are that it will probably stick around for the foreseeable future (certainly for the next 10 days, and plausibly for the next 2-3 weeks). This may sound a bit odd to those accustomed to the typical weather prediction mantra that anything out beyond about 7-10 days is essentially unpredictable. But recent evidence suggests that under certain circumstances, large-scale atmospheric predictability can be much higher over longer periods. The present instance of prolonged, stable ridging near the West Coast appears to be one of these situations, given the remarkable multi-model ensemble agreement that the large-scale flow pattern is unlikely to change much through at least mid-February (and perhaps even longer than that).

One atmospheric dynamics-related reason for this high confidence: the Madden-Julian Oscillation (MJO) yesterday reached its highest amplitude in recorded history, and appears to be be “stuck” in a phase that favors strong West Coast ridging and warm/dry California conditions. MJO-California weather linkages are a complicated topic that’s a bit beyond the scope of this brief blog post, but there are some good resources out there on the web for those who are interested in learning more.

The infamous precipitation “donut hole” over California will most likely persist for the foreseeable future. (NCEP via tropicaltidbits.com)

This doesn’t mean that it will be completely dry across the entire state, but it does suggest a very high probability of far above average temperatures and well below average precipitation during what is typically the wettest part of the year in many parts of California. This appears to be an unfortunate case where the seasonal forecast models–which predicted a warm and drier than average winter in California, especially across the south–did a pretty good job. As many folks have pointed out, California’s seasonal precipitation is often dictated by the occurrence of just a handful of strong storms each year–so it’s still possible that a robust storm sequence in late February (or another “Miracle March“) could bring a remarkable turnaround in short order. But while that possibility remains on the table, the odds are long.


Some brighter news: a Weather West milestone!

Recently, the Weather West blog hit a bit of a milestone: 10 million visitors since 2006! Even more impressive, I think, are the 250,000 (and mostly on-topic!) comments that have accumulated (occasionally over 5,000 per blog post!). That’s a real testament to the engaged community that has flourished here over the years. I want to sincerely thank everyone who has helped make this site what it is today!

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  • Boiio

    Currently 33F up at the top of Mount Tam and 28F at the top of Mt. Hamilton. NAM and GFS showing a blob of precip coming ashore later tonight. Maybe some snow-capped peaks in the Bay Area tomorrow morning? https://uploads.disquscdn.com/images/70f7b711f175d454860325febacee26e30df370f7710e1d275bc32153f6694bb.png

    • Craig Matthews

      I was just going to post the HRRR for the same thing. Both NAM and HRRR show snow up where “Alanstorm” lives. Valley snow for interior Mendocino, Lake, parts of Sanoma co. by early morning. I think Daniel also mentioned this earlier in a tweet. The timing looks perfect with cold air inversion in the valley and incoming cold system from the nnw bringing the precip just far enough inland for valley snow. Hopefully we get some good pics out of this too if it happens.

      • Boiio

        Yeah, the timing looks ideal. This setup reminds me of a storm back in January 2002 when it snowed down to the valley floor in Santa Rosa and Petaluma.

    • jstrahl

      WTH? Totally not forecast!

      • janky

        Daniel forecast it yesterday, check the comments

        • jstrahl

          Well, not happening, per NWS most recent forecast, within the last couple of hours.

  • hermit crab

    Canyon clearing only half finished…ouch.

    This is about Carpinteria but isn’t only for Carpinteria. Whether or not we get rain is very important. Our safety is at stake. We must watch the forecast. Don’t panic but take it seriously.


    • celo

      Sounds like they got a lot of the work done. Just have to finish off the Santa Monica Creek Flood Basin.
      It’s funny, when I was a kid I would pass through Carpinteria and think how ugly the concrete channels are and how they should of let the creek channel be in it’s natural state. Like in Montecito.
      I don’t think that anymore.

  • DrySprings6250

    High of 29 currently 22. We are now at 48hrs of below freezing temps which is more time below freezing than all of June-December 2017 IN TOTAL. ???? except for January…..2017 sucked donkey balls!!!

    • Cap’n

      Down to 19F here and I think a high of 27F. Extended showing highs in the 30’s with a few highs in 20’s with lows in teens and single digits for like 10 days. It would be garden variety temps for Truckee but given that it’s getting into late February it’s impressive. Now Ian if we can just get some major snow all will be right in our worlds.

    • Phil(ontario)

      Can green valley lake freeze over in the coming week?

      • DrySprings6250

        Yes as does Arrowbear Lake at my elevation – their small size makes it pretty easy and with any snowfall more than a few inches it’s a sure bet. A few times I have seen both froze over as clear ice just from cold and wind but usually it’s with a heavy snowfall. Shit they use to freeze over from the first heavh snowfall in November or December straight through to March or April!

  • Based on current temperatures, looks like snow is likely tonight after all in the Bay Area hills (certainly above 2000 feet, and perhaps locally down to 1000 feet or a bit under once again). Ukiah and Clearlake could see some accumulations, too…maybe some of the highest valleys in Monterey, Napa, and Sonoma counties too.

    • B_R

      Is it likely to be warmer or colder or the same as last night in the East Bay? Last night it seemed to be colder in the hills than near the water, and near the water there weren’t many stations showing below 35F as their lows.

  • weathergeek100

    Meanwhile, in Washington DC where it’s currently 61 at this hour, will be approaching 80 degrees tomorrow.


    • Unbiased Observer

      Good, let em’ fry.

    • alanstorm

      No doubt will be some snowmelt flooding as result of sudden onset of unseasonable warmth, right after extreme cold…….wait a sec- that sounds like California!

    • Fairweathercactus

      Let them bake they will enjoy it.

    • Dan the Weatherman

      It would seem like with such warm weather there, we should be getting storms here!

  • Great Winter of 2017 (SMC)

    The trickery of the GFS is something unseen, so much change from day to day and run to run

    • Fairweathercactus

      I am only at hour 192

    • SoCalWXwatcher

      00z is strange & exciting.

    • RandomTreeInSB

      +wet long range
      +modestly wet within 10 days
      -storm track pushed more inland
      -Arctic still cooking

      Next model train departs in 6 hours, grab a ticket and enjoy the ride. If not, wait for the next one 6 hours later.

      • SoCalWXwatcher

        We need more safety restraints for riding these models lately. The seat belt light should remain on for the remainder of the flight. By 06z, I expect the oxygen masks to drop.

      • jstrahl

        +wet long range
        -storm track more inland

        Aren’t these two contradictory?

        • RandomTreeInSB

          Fixed. Should say within 10 day window.

        • SoCalWXwatcher

          00z GFS – Late February storms colder/more overland track. Early March wetter. If you don’t like it, just wait 6 hrs.

          • jstrahl

            Though the one in 6 hours may satisfy you even less. 🙂

      • Cap’n

        All Aboooooooooooard

        • Yolo Hoe

          I knew 00Z would be a good one after reading Schlaepfer’s update and his reference to 2006 — what a beauty

      • alanstorm
  • alanstorm
    • Bob G (Gustine)

      Lol. The 00Z is a dream for you

      • alanstorm

        I’m gonna carry a picture if it in my wallet….

    • jstrahl

      Looks like previous forecasts for March 1, March 3.

    • We always wake up before it happens.

  • SoCalWXwatcher

    Portland with 3” on the ground as of 8pm.


    • Cap’n

      Friend in Olympia got snow again today. If nothing else this cold is exciting just cause it feels so new and different. I think we’ve got an exciting month ahead.

      • Pfirman

        Thanks for taking up the Tyler mantle. He has been missing in action, or non-action.

        • Sokafriend


        • Jason Jackson Willamette

          He was going to get a tour of the NWS office in Monterey. Maybe they hired him on the spot and put him to work on the dark web. You know, where G. Soros is supposed to control the weather….

    • Mark

      Well this is the perfect setup for the Pacific northwest to get lots of snow.

  • Cap’n

    A friend of my wife’s posted this on FB from Snow Valley on Saturday. All the more reason to snow dance until our feet won’t hold us up anymore.


    • Charlie B

      Snow Valley? Looks more like Grass Valley.

      • Grass would imply some form of moisture present. Dirt Valley.

    • DrySprings6250

      ??????????????? it’s been freezing ever since so at least they’ve been able to have the guns on 24/7 to keep payroll going for some locals….

    • Cap’n

      I debated posting it, but I figured it could be peak into the future of California skiing, which will really be the least of our problems.

      • matthew

        On the bright side – year round mountain biking.

  • Great Winter of 2017 (SMC)

    Euro brings showers to the Penninsula, would be the first rain in 25 days

  • Jason Jackson Willamette

    Extraordinary rains happening in the middle of the country. It was in the 70’s today across the south. Right now it’s 70 degrees at Muscle Shoals, North West Alabama Regional Airport! Needless to say, lots of flooding.

    Meanwhile, out West – our old high is moving north, and getting kicked our way is the storm system that pummeled Hawaii for three days, causing flooding there.

    Let the fun begin https://uploads.disquscdn.com/images/c79512f9901eb6967625441c4c3e33dc197c592163d2364ef250f79be4ddae84.jpg


    • jstrahl

      How do you see that storm kicking our way? I don’t see anything of the sort.

    • alanstorm

      One can only dream….sigh?

    • It’s effing up my SpaceX launch visibility ;,0

  • SpaceX launch cancelled, again, this time at the last possible minute. 2 minutes after I left my house . Arrived and launched the stream AFTER climbing up a hill. Bleh. I guess I’ll film some snow clouds.

  • DrySprings6250

    24F, never got down to the 14f that was forecast. Chances of snow was all but removed for the rest of the week except 20% Friday.

    Although the lightest of snow is falling right now, I counted a dozen flakes on the deck railing.

    Here’s to a real storm next week, please..

    • Bombillo1

      Somehow we have managed to have a change in our weather that includes no rain. Storms with no water, snow with no snow.

      • What is called a storm now seems to be a dirty ridge with virga

      • AlTahoe

        Yep but the cold air is refreshing. We haven’t seen any cold since Dec 2013.

        • Cap’n

          I recorded 8 subzero days between Thanksgiving and Christmas 2015, but besides that we haven’t had a true cold snap that lasted weeks in forever. 9F when I left home this morning, 14F at work.

          • AlTahoe

            Hmm I am trying to remember if we got below 0 during that time period or not? Dec 2013 I recorded -13F at my house. Yesterday the airport was down to 0 officially. South lake averages 2 days of below 0 a year so it has definitely been a while. In 2011 I recorded a -2F in Mid to late March after one of those big storms. Also Thanksgiving day 2010 was something like -7F

      • jstrahl

        Anything, except precipitation.

      • Phil(ontario)

        Yes. Another feature this year is when the storm door is open, there are no storms. All things coming together just right for an all time record low season.

        • Bob G (Gustine)

          I don’t recall a storm door ever truly being open this year. I think there might have been times it was in January. The storms weren’t all that impressive and the jet didn’t help at all.

    • matthew

      4F when I rolled my butt out of bed this morning. Currently up to a blistering 8F. Cold with no snow is worse than warm with no snow, IMO. Time to find some indoor projects…

    • AlTahoe

      It was about 5 – 15F warmer up here this morning as well compared to yesterday. Weird as we had no cloud cover.

    • matthew

      Single digit temps
      Pine beetles scream in anger
      The forests rejoice

      That does it, I really need a cold weather hobby. Haiku is not it.

  • AlTahoe

    Hmm this is interesting. Lowest value ever was Feb 2006 and after that we had a really cold and snowy March. Hopefully we follow that pattern.


    • jstrahl

      If only the future simply repeated patterns from the past.

    • MJO went into COD in March 2006, EMON puts it there this year.
      March 2006 NH heights looks almost rubber-stamp to GEFS 06Z NH heights for March 3rd.

      The BIG IF: NO bridge between the ridge over Greenland and Western Pacific. If so we will get nothing but cold air and weak-assed spitters if the polar jet can’t come down over the top of the ridge and out over water. If there is something like 2006 in store for March 2018 I can’t emphasize enough that ALL the jet energy came from the Polar Jet in March 2006.

  • White Lightning

    Apparently the SPC has a threat of thunderstorms for the Sac valley tomorrow. Anybody know why?

  • nunbub

    Anybody know an inexpensive SUV tire chain supplier between Sacramento and Truckee? (weather related, I swear)

    • matthew

      Just go to any generic auto parts store (O’Reilly, Kragen, whatever) and buy the most basic set they sell.

    • rob b-Truckee/East Bay

      You could try some place like Les Schwab which I believe may have a return policy if you don’t open them (don’t need them). You’re better off looking Auburn and below because as you head up the mountain the price goes up. You can also search your tire size on Amazon and sometimes get a good price.

  • Bartshe

    Distracted by cold temps and very light precipitation in next 10 days…. March miracle nuh-uh: https://twitter.com/WRCCclimate/status/966073650251120640

    • Phil(ontario)

      Down south we are just hoping to not set the record for least precip ever recorded.

      • alanstorm

        Geez. That’s awful.
        For me, it’s all about how soon the wildfire season starts.
        Unfortunately, it’s looking rather soon up here, & I’m reminded of the reality of the danger every time I drive to Ukiah thru the burnt scorch-zone of Oct 9

        • JMS (NE Fresno)

          Did the fire season close?

          • alanstorm

            Yes, we got enough rain in November & January.
            However, with this historic dry winter, if we don’t get a Miracle March, we’re looking at a sudden start after the next heatwave.
            Then it will be red-flag warnings as far as the eye can see

    • Nathan

      So you’re saying there IS a chance!!

    • Bob G (Gustine)

      Not sure why people focus on all or nothing. Yes, it is highly unlikely we will reach a normal year. If we reach 70% it would still be much better than 20%.

      • Patrick from Stockton

        Absolutely, considering the record setting rains and snows we got in Nor Cal last year.

  • jstrahl

    39 deg F low in central Berkeley this morning, a perfectly clear sky mocking the (NWS) forecast on the 8AM KPFA news of “mostly cloudy with a slight chance of showers.” Remember the chart posted here late yesterday showing green and even yellow over the Bay Area? Fantasyland is now *anything over 12 hours*.

    • weathergeek100

      Seriously, right? I woke up (here in Emeryville) and not a cloud in the sky! I was actually quite hopeful for some precip despite the tiny 20% chance of showers in the forecast and the fact that we got some spits of rain on Monday when rain wasn’t even in the forecast. This morning? Nothing…not even clouds!

    • Boiio

      Hey, I got 27 drops of rain over in San Rafael. I’d call that some serious forecast verification!

    • Rusty Rails

      A large field of showers and virga was skirting the coast here at sunrise. Not much was making it into the heart of the Bay Area judging by radar.

  • Shane Ritter

    12z really takes it to the bank. Wow.

    • Freddy66

      yup….the storm in the first few days of march will be great….cough….cough

      • Idaho Native

        There were no storms like this on the horizon as we went from January to February that’s for damn sure.

        • jstrahl

          The tease machine was off.

    • jstrahl

      My source doesn’t show it al, i get a “null graphic” at the end, meaning it’s still being loaded there. Same old thing, storms, storms,….. next month.

    • AllHailPresidentSkroob

      Is that a good reference or a bad reference… I’m jaded so I don’t know if you’re indicating we’re going to get wet or indicating the inverse…

      • This winter season there has been no money to beg, borrow or steal to make a deposit.

      • Shane Ritter

        Good storms. Hopefully feet of snow.

      • DrySprings6250

        Right! Haha!

    • Patrick from Stockton

      Yeah I just caught up on the last 3 runs. They all look pretty darn good. Trend going in the right direction again.

  • Charlie B

    My favorite Alaska weather blog had an article on 2/7 with the title “Warmth to Return” and discussed the then upcoming SSW event. Two weeks later consider this: According to the NWS, Reno’s average temperature yesterday was 24.5 (they actually rounded up to 25, but let’s use 24.5.) Here are some temperature numbers yesterday from places in Alaska (roughly from the SE panhandle and then south to north: Annette 32, Sitka 33, Yakutat 28, Kodiak 39, St. Paul 36, with a record high of 40, King Salmon 34, Cold Bay 34 (should be renamed “Cool Bay” perhaps?), Bethel 27, McGrath 26, Fairbanks 25, Nome 29, Kotzebue 30 with a record high of 34, and finally Utqiagvik (Barrow) 25 with a record high for the date of 31. It seems like they nailed that one.

    • We haven’t experienced a recorded SSW event that had open ice between Scandinavia and Greenland maybe that has had something to do with it.
      The relative tropospheric/ surface heat is coming from this same area as well as over Eastern Siberia.

  • alanstorm
    • Pfirman

      Really nice place and really crazy event.