With very heavy precipitation expected next week, particularly on the western side of regional mountains, major flooding is being forecast.
Over the next five days, the UW WRF model is forecasting more than ten inches over the western side of the Cascades (see below).
Are you sitting down? Ready for a shock? Below is the ten-day accumulated precipitation forecast for the region. Some locations are expected to receive 15-20 inches in total.
That means flooding.
The super-heavy precipitation on Tuesday will be associated with this region being hit by one of the strongest atmospheric rivers in a long time (Tuesday at 7 PM shown):
The Gogzilla Atmospheric River. Trained meteorologists call this a GAR.
This is a serious event, and those of you in vulnerable locations should make preparations.
A good effect of this major precipitation event is that local reservoirs will gain an enormous amounts of water. All the western Washington reservoirs should fill to at least normal levels and a major filling of the Yakima system will occur.
And what about snow in the mountains?
ReplyDeleteNobody cares. Thats akin to saying "can we finish our desert before disembarking?" As the titanic is sinking
DeleteWe need the snow to carry us through the summer. ECMWF up to the 14th is showing a lot of snow above 5000' - good but not as low as needed to insure snowpack will last and provide good skiing.
DeleteThere is plenty of time to get snow, right now we need a major refill the reservoirs...which will be happened during the next week.
DeleteIn past events like this river flooding and road washouts have closed roads for days leading to ski areas, like SR410 (crystal) , SR2 (stevens), and SR542(baker). OR skiers desperate for snow wanting to ski in WA could be denied access if I5 by Centralia floods.
DeleteRefilling reservoirs during the late fall is fine and good if the goal is the release of water from the reservoirs to improve salmonid habitat - because that's exactly what will happen. Normal mountain snowpack ensures that reservoirs receive plenty of runoff from snowmelt during the mid spring thru early fall - the growing/dry season - when it's needed for agricultural purposes/human use.
DeleteThanks for this update Dr Mass. it is also useful to know what the snow levels will be associated with the storm
DeleteLong range looks even milder next weekend with freezing levels 2000+ meters by Fri/Sat. I think the earlier models underestimated how warm it was going to be regarding the big snow accumulation. December is the new November with the most frequent storm parade being sub tropic moisture.
DeleteI think this suggests there will be heavy snow in the cascades. But IANAM (I am not a meteorologist)
ReplyDeleteDr Mass,
ReplyDeleteAny thoughts on where the snow level (not to be confused with the freezing level) will be for these coming events, especially in light of the diabatic cooling mechanism? This could be the key determinant of how much rain-on-snow occurs, and consequently, how much flooding we see.
Reason I ask is because during extreme precipitation events, I've seen the snow level be almost 1,000m (3,000') lower than the forecast freezing levels. One example was the solstice atmospheric river event in 2019, where Alison Pass on Hwy 3 in BC set a new 24 hr record for precipitation (107cm snow / 68mm SWE). There were multiple hours of 10cm/hr (4"/hr) snowfall accumulation. Manning ski hill reported 134cm (52.7") in 24 hrs!!!
There is an excellent reference article on this event written by Paul Harwood and Matt MacDonald: "Rivers in the Sky." in The Avalanche Journal Vol 126 pp. 23-26.
We have had some big floods in December. 2007, 2010 and 2023 come to mind.
ReplyDeleteis the wind happening right now a precursor? It is really windy!
ReplyDeleteThis almost reminds me of the major flooding of 1990, though that happened in I think Nov, then early December, the big snow and hard freeze for almost a week afterward and all that water up in Skagit/Whatcom etc counties (and Fir Island) all flooded, then froze over and lots of farms lost livestock as they froze in the frozen flood waters.
ReplyDeleteThis could get interesting and a mess for us commuters to work, just in/around Puget Sound Corridor.
This is off topic, but seconding Carly - what's with this wind? My gauge has shown 50 mph not calibrated but last year peaked at 61, so this is in the same ballpark This is the worst we have seen since the big blow last year and there was no real warning except for 15-20 mph on the news. Would like to know if the models picked this up.
ReplyDeleteCat Stevens, years ago, wrote a tune with lyrics that I will now slightly modify, in order to comment on my area's pending lack of rain..."I'm being followed by a RAIN SHADOW, RAIN SHADOW, RAIN SHADOW"!!!
ReplyDeleteA few days ago a site called Mountain Forecast was predicting some 190 inches at the top of Mount Rainier over 6 days, with a maximum of more than 80 inches from Tuesday to Wednesday afternoons, about 24 hours -- which in theory would be a record. But then they also brought that down. Are you aware of that site? Is it credible? I wonder how high you have to go before most of the precipitation is below you . . .
ReplyDelete