We are now solidly into mid-winter--a good time to check on the status of precipitation over the region.
Let's start with the total cool-season precipitation since October 1, the beginning of the "water year" (see below).
The majority of the western U.S. has received above-normal precipitation, with the North Cascades and the Los Angeles area being substantially wetter than normal.
There is one major dry area: western Oregon.
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The key driver of these patterns of precipitation and temperature has been persistent high pressure aloft over the western U.S, and the persistent trough of low pressure aloft over the eastern U.S. This is illustrated below, which shows the difference from normal at 500 hPa (roughly 18,000 ft). Higher than normal pressure is indicated by the yellow; blue and purple indicate the oppoosite
High pressure is associated with sinking and warming aloft. It also contributed to dry conditions.
The complex distributions of precipitation and temperature have created an even more complex distribution of snowpack over the western U.S.
The southern Sierra Nevada is fine, and eastern Washington and the Rockies are just a little below normal.
But the real problem area is found over Oregon and northern CA, where the combination of a lack of precipitation AND warm temperatures has resulted in snowpack areas below 40%.
Looking forward, the latest European Center forecasts are predicting substantial precipitation along the Washington Coast, over southwest BC, and the north Cascades.
But far less to the south, where the real deficiencies exist.
Oregon folks should not panic yet.
I can remember a number of years that were dry until early February, but made up most of the deficiency in late winter and spring.
Can you explain a bit more about how the so-called central Cascade mtn "low" snow pack will affect irrigation and power generation during the rest of this year?
ReplyDeleteHard to tell. All we know right now is that unusual weather seems to be the norm everywhere in the U.S. including the distortions caused by a wavy and sluggish jet stream.
DeleteCliff: concerning the Yakima River Basin water supply situation, you might do well to talk with the Yakima Burec Hydrologists to get their take on the situation. The full reservoirs supply close to half the needs of the district for the upcoming agricultural growing year. The current situation is good, BUT, there appears to be very little snow in the lower elevation areas that supply the other half needed to prevent rationing to the junior water districts later on. Here's hoping we get more snow lower down as the winter progresses.
ReplyDeleteThanks for the update on our winter precipitation. It sounds like Oregon is in need of some assistance from Mother Nature in order to boost the snowpack and give the lowlands the rain they need.
ReplyDeleteGood to see the reservoirs fill up so much in December to get ahead of the poor snowpack.
ReplyDeletehttps://cliffmass.blogspot.com/2026/01/a-very-moist-california.html?m=1
ReplyDeleteHow does the current situation reconcile with your post from a few weeks back that everything was going well. Are water resources still stockpiled, or are there needs to conserve?
If Yakima is currently at a higher value than it reached for the entirety of last year, are you capable of extrapolating out beyond that data point? You can also easily look up the current reservoir data for yourself...
ReplyDeleteIn respect to the "snowpack" (SWE) data-driven maps (and water resource forecasts driven by 'evidence' along those lines), I think the date-ranges used can lead to significant distortion. Looking at the NRCS exhibit for my watershed (WRIA 1 that includes Mt Baker), the date range for the "58%" begins at 1991. Waal ...Mt Baker had (and may still hold) the world record snowfall 1998-99, 1,140" of snow. We've had other high snowfall years within that date range. Comparing this year's snowpack to a date range that includes outliers doesn't sit well, scientifically (IMHO). The Pacific Northwest (some zones more than others) have a very wide "range of normal" (wet years, dry years). I can't help but wonder what how these statistically driven exhibits would (or might) vary given different "timeframe" runs. AND, further (I constantly do "rag" about this) - where it comes to water resources, the melt of frozen water (ice and snow, including glaciers) may correlate to, but most certainly does not "drive the hydrogeology bus," so to speak. Rain, precipitation - WET water - is what flows. A fair share of snowpack actually evaporates...and so on.
ReplyDeleteThe major point here is that I think the PRECIP maps matter most, and much of the PNW is in very good shape in respect to "what flows" (infiltrating into soil (hydraulic baseflow), and reservoirs). Just sayin' - there's weather, but hydrogeology's where 'rubber meets the road'.
In the cloudy and high humidity climate of the Nooksack basin, only a small fraction of snowpack sublimates directly to vapor (~5%). The vast majority melts and runs off or infiltrates just like liquid precipitation and, crucially, it does so during the drier portion of the year when rainfall is scarce.
DeleteSnowpack in the Nooksack basin has decreased substantially during the past 30 years at lower elevations. Annual SWE at the Elbow Lake SNOTEL site (3050') has decreased by about 36% since 1996. At higher elevation sites, the decrease is less dramatic and more influenced by aspect. The Wells Creek SNOTEL site (4040'), sheltered by high ridges and cliffs to the south and west has seen only 5% decrease in annual SWE since 1996. The higher elevation Middle Fork Nooksack SNOTEL site (4940'), near the summit of Lookout Mountain, is exposed to the afternoon sun with no higher terrain to the west and annual SWE at that location has decreased by nearly 15% since 2003. The Mount Baker Ski Area (Heather Meadows 4220'), with its northeasterly aspect is the most sheltered of all and as well as being exposed to the heaviest precipitation in the basin, has only seen a decrease in annual snowfall of about 5% since 1970.
As the climate continues to warm, however, elevation and aspect will provide gradually less mitigation and even the higher and better protected sites will begin to see more dramatic decreases in snowpack. It is simply a matter of time as Cliff as mentioned in numerous past blogs.
Meanwhile, eastern United States and other parts of the world are getting pummeled with snow. I wonder what a north polar map (most particularly an animated one) would show (illustrate) about global snow pattern(s) over time. I did a little Google'ing and (WOW) Moscow - Russia - has, and this is a quote "In January 2026, Moscow experienced its snowiest January in over 200 years." There's a BBC video dated Jan 21 that's worth seeing:
ReplyDeletehttps://www.bbc.com/news/videos/c8e5901727zo
Cliff,
ReplyDeleteBack during the Autumn, the winter seasonal progs from both GFS and ECMWF were for colder than normal temperatures across the Pacific Northwest. Consistent with moderate La Niña. It seems those forecasts really missed on temperature. Is that due to the unpredictability of the NW high/ NE low that you highlight in today's post? If one used only this winter's results, it would seem that those seasonal progs are not very skillful. Comments please.
Up to yesterday, the forecast was calling for rain almost every day for the next week where I live on the central Oregon coast. Today, instead of rain, we had a nearly 60-degree sunny day, and now only one day in the near future has rain in the forecast. My, admittedly anecdotal, observation is that over the 21 years I have lived here, the rain has shifted further north, and we are more often than not at the southern edge of most major systems.
ReplyDeleteThe winter of 2015 and this winter might have some notes to compare. That ridge that dominated the storm track the second half of January looks more like a summer feature. The jet stream seems like it is already moving well towards summer time mode. Pilots and farmers are taking notice of it. Anyway, building a respectable snow pack at this point seems like a coin toss.
ReplyDeleteYakima basin can store about 1 million acre feet of water when full. But full irrigation requires 2.5 million. Without a good snow pack to recharge the basin it will reduce yields.
ReplyDeleteGood comment Weather Devotee. Been trying to get that message out - it used to be that water
ReplyDeleterationing for the junior districts could be needed if there is less than 1.8 million acre-feet runoff for the year. Will be interesting to watch how this plays out this year!