April 28, 2024

Substantial Late-Season Mountain Snow Ahead

Most folks are not thinking about substantial snow in the mountains during late April and early May, but such snow will be a reality this year.  

During the next 48-h, 3-8 inches will fall on the Cascade passes and more is predicted during the next week or so.

Stevens Pass on Sunday Afternoon

The key source of the upcoming cold, snowy weather are two upper-level lows that will move in tonight and Monday night (see upper-level maps at 2 AM Monday morning below).   This kind of pattern has been rare this El Nino winter.

So how much snow could we expect on Monday and early Tuesday?   

Below is the 5 AM Sunday accumulated snowfall forecast through 5 AM Tuesday of the high-resolution NOAA/NWS HRRR model.  

Impressive.    Over a foot at higher elevations. 4-8 inches in the passes.  Large values in the mountains of southern British Columbia as well.

The UW high-resolution modeling system has a similar solution, but we have even more to offer:   we run an ensemble of many forecasts to understand the uncertainty of the forecasts.   Using this system, the snow accumulation at Stevens Pass (around 4000 ft in the central WA Cascades) is shown below.  

Some uncertainty, but the average is about 6 inches for this event.


How unusual is a half foot or more of Cascade Mountain snow this time of the year?

To gain some insights into this interesting question, below is the daily average and daily extreme snowfall at Stampede Pass from 1944 to 2016.   

On average, this site receives about an inch around May 1.  But extreme days this time of year have received 10-15 inches.  So getting some snow at this point in spring is no big deal.

In any case, expect a significant bump up in regional snowpack by midweek.

But the impressive thing is that the snow and cold are not over on Tuesday.  The latest model forecasts have several more cold lows moving through during the subsequent week.

As a result, a LOT more snow is expected to fall.  For example, below is the predicted accumulated snowfall for the next five days from the highly skillful European Center model.  ANOTHER FOOT (or more) at some mountain locations.


And the extended forests after that have even MORE snow.

Regional ski areas should think about reopening for glorious May skiing.

And no, global warming does not cause bountiful May snow. 😉

_______________________________

Announcement:  There will be no Northwest Weather Workshop this year.  

Why?  Because we lost two important partners.  The Seattle National Weather Service Forecast Office has told me they are no longer interested in hosting and participating in this regional weather gathering.   And the other partner, the Puget Sound Chapter of the American Meteorological Society, has died.    I am looking for new partners for next year. Keep tuned.

22 comments:

  1. Is climate change (the "go to" blame for almost all ills, real or imaginary) just another way to say weather? Asking for a friend.

    ReplyDelete
  2. So far, this is spot-on. I'm seeing significant snowfall here in the mountains right above Glacier, at an elevation as low as 1400-1600 ft (I've taken some snapshots). And it's been cold and rainy here in the valley: overnight low was 32.5 F and the 24-hr rainfall was .70" at 7 am (I report to CoCoRaHS). Some of the locals will be delighted to do more cross-country skiing.

    ReplyDelete
  3. Too bad about the Weather Workshop. Best of luck getting it going next year.

    ReplyDelete
  4. Hi Cliff, I am curious about something I saw on the UW radar loop this morning. At 6 AM it showed scattered rain falling well south of the San Juan Islands. Then at 6:45 a large cell appeared over Lopez Island, from the direction of Vancouver Island, with intense rain and hail mixed. Where did that come from and why did it not appear on the radar earlier? Did it just form above the island or is there a blind spot in the radar? Thanks,

    ReplyDelete
  5. Honestly this is really hilarious after that equally hilarious drought emergency declared by the state. Rain and snow and more snow lmao.

    ReplyDelete
  6. I should have not removed the chains from the trunk of the car.

    ReplyDelete
  7. Someone in the Seattle Times comments a while back said that late season snow doesn't help with the summer water supply as much as snow earlier in the season. Is there any validity to this? The premise didn't make much sense to me.

    ReplyDelete
    Replies
    1. No....that does not make any sense. In fact, it is just the opposite.....late season snow is FAR more valuable.

      Delete
    2. The phrase "the premise didn't make much sense to me," should apply to anything the Times puts out.

      Delete
  8. Cliff, in your April 24 "Drought Buster" post, you said, "I suspect the snowpack will increase to around 80% of normal over Washington State and more than 100% of normal over much of Oregon within roughly 10 days." Six days later, we're still below 65% of normal statewide. Do you expect a much more dramatic change in the next few days?

    ReplyDelete
    Replies
    1. PS: Just checked on the SNOTEL site. The region is now up to 76%!

      Delete
    2. "Be patient" is great advice, thanks.
      What do you mean by "the region" in this case?

      Delete
    3. The Pacific Northwest:
      https://nwcc-apps.sc.egov.usda.gov/imap/#version=169&elements=&networks=!&states=!&basins=!&hucs=&minElevation=&maxElevation=&elementSelectType=any&activeOnly=true&activeForecastPointsOnly=false&hucLabels=false&hucIdLabels=false&hucParameterLabels=true&stationLabels=&overlays=&hucOverlays=2&basinOpacity=75&basinNoDataOpacity=25&basemapOpacity=100&maskOpacity=0&mode=data&openSections=dataElement,parameter,date,basin,options,elements,location,networks&controlsOpen=true&popup=&popupMulti=&popupBasin=&base=esriNgwm&displayType=basin&basinType=2&dataElement=WTEQ&depth=-2&parameter=PCTMED&frequency=DAILY&duration=I&customDuration=&dayPart=E&monthPart=E&forecastPubDay=1&forecastExceedance=50&useMixedPast=true&seqColor=1&divColor=7&scaleType=D&scaleMin=&scaleMax=&referencePeriodType=POR&referenceBegin=1991&referenceEnd=2020&minimumYears=20&hucAssociations=true&relativeDate=-1&lat=44.009&lon=-118.312&zoom=6.0

      Delete
    4. Thank you. Still a ways to go but I'll follow your advice and be patient 🤞

      Delete
    5. Cliff - I've been patient as prescribed. You were mostly right about Oregon, but mostly wrong about Washington, where snowpacks are now even lower (relative to historical means) than they were when you predicted an increase to 80%.

      When it comes to Washington mountain snowpacks, my take-away from this is that the action is all in the winter, when snowfalls are measured in feet, not inches.

      WRT state agencies like Ecology, who are charged with making forecasts for water users, it appears reasonable for them to look at the situation at the end of April and say, "This is it, this is what we have to work with this summer....."

      Delete
    6. Jerry..the NW is not at 82% and was higher. Here is the proof:
      https://a.atmos.washington.edu/~cliff/Screenshot%202024-05-16%20at%2010.42.35%e2%80%afAM.png
      ..cliff

      Delete
    7. As I said, Oregon has plenty of snow, Washington does not. Central Columbia and Upper Columbia drainages are now at ~50% of normal or less. It matters to Washingtonians.
      https://www.nrcs.usda.gov/programs-initiatives/sswsf-snow-survey-and-water-supply-forecasting-program/snowpack-and

      Delete
    8. Jerry..... your analysis is not complete or adequate. Much of the snow that melted was retained...and available. Or if the precip fell as rain instead of snow, it was retained. For example, the Yakima Reservoirs are about 80% of normal. Sufficient water this year. WA Ag is doing very, very well, with excellent crops expected. They is really not problem...cliff

      Delete
    9. I understand that Washington's reservoirs are full and farms will be fine. The state's declaration of drought helped to make that possible. Among other things it reduced dam releases that otherwise would have been routine to help fisheries. Forewarned is forearmed.

      As the DoE declaration pointed out, this past winter has been our eight warmest since 1895, and there is very little prospect of a turn-around before the next wet season. Even by El Nino standards it isn't business as usual. Today's updated NOAA climate projections continue to point toward a likely warm and dry summer in our region. We can easily deal with a low-snowpack year but only if we accept that reality.

      Cliff, I enjoy your blog and have learned a lot from it. I teach a UW course on Environmental Change and when I think about what to say, I try to include your skepticism in my decision-making process. But I see you making the same mistake over and over again. Your "Drought Buster" post was the third time this year that you forecasted significant snow events (which arrived as predicted) that you thought would restore our snowpack to something close to normal (none of them did). Climate skepticism can lead to bias like any other viewpoint. The world is warming and the most accurate weather forecasters will be the ones who factor that in.

      Delete
    10. Jerry..I would suggest that the drought declaration is not only scientifically non-rigorous, but has little impact. Regarding my "mistake": one has to look at the water problem holistically...you are just looking at SWE in the mountains. I believe that is an error. Rain that is captured in reservoirs, etc. is just as good as snow. The fact that there are little apparent impacts of this "drought" kind of proves my point..cliff

      Delete

Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

More Rain for the Northwest is Good News for Wildfires

After a very pleasant dry spell, another rainy period is ahead for the western side of the region and the Cascades on Friday and Saturday.  ...