In act one of this meteorological drama, yesterday and this morning brought heavy rain and flooding to many sections of western Washington. Well-predicted days in advance.
But the weather prediction models indicated that this would be a two-act event, with the second act being far more serious. The curtain is about to rise.
Take a look at the precipitation totals of the first act (last two days, below). Some areas received 7-8 inches.
Many local rivers are now at flood stage, with some at record levels (black dots are record levels, blue are 90th percentile or greater, with normal being 50th percentile)
The media is full of pictures of flooded roads, such as in the Snoqualmie Valley. A once-in-1-3-year event.
But this is just the meteorological appetizer course. The real action is about to begin: a second, stronger event that will throw massive amounts of rain on saturated surfaces.
Consider the total precipitation from the UW ultra-high resolution modeling system for the 72 h start this morning at 4 AM (shown below).
Wow. There are going to be some happy ducks. Large areas will get 10 inches of rain or more, particularly in the Olympics and northern/central Cascades.
Serious flooding is inevitable.
How can I be so sure? Because of the use of ensembles of many high-resolution forecasts. If they are all on board with heavy rain, my confidence grows.
Let me demonstrate this to you. Here is the ensemble of accumulated precipitation at Humptulips on the southwest side of the Olympics. A huge amount of precipitation (about 6 inches), most over about 12h. Not much variance in the forecasts.
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The Yakima River is now at flood stage (see below), and in a few days the entire system will be full to normal levels.
Thank you for the update, Professor! The rainfall totals are very impressive, and our rivers are definitely making their presence known. I hope everyone stays safe out there!
ReplyDeleteIs 2025 becoming one of the wettest year in our region's meteorological history?
ReplyDeleteWell, we have a lot of catch up to do. Still behind statistically believe it or not.
DeleteBut drought.gov says we are in severe drought
ReplyDeleteFloods. Surprisingly, don’t often help with droughts.
DeleteYakima, 23+ inches. Wow!
ReplyDeleteIf these two rainfall events had happened to butt heads with a Frazier River outflow, how much lowland snow would have resulted? I have been having visions of the 1950 three-day record of almost 26 inches.
ReplyDeleteWhat's astonishing is the pronounced rain shadow has made the Everett area feel like we dodged a bullet. Sure, it's been wet, but just about every day since Thursday has also had a functional dry period as well. Unfortunately, the watersheds for the local rivers are getting hammered (the rain shadow can only do so much).
ReplyDeleteIt's already done too much
DeleteChecked Mission Ridge webcam. Big river in the middle of the artificial snow field. Sigh, skiing not looking good this year.
ReplyDeleteAre atmospheric rivers always likely to generate rain in the mountains. Will they ever generate snow?
DeleteThey tend to have tropical origins and therefore warm air. The freezing levels associated with atmospheric rivers are typically high as a result, so they're not great snow makers
DeleteThe atmospheric rivers have an alternate name, Pineapple Express, which is because they generally come from the vicinity of Hawaii. Hence they bring some of our warmest rains with freezing levels often as high as 9000 feet.
DeleteThey often come from the subtropics or even from the vicinity of Hawaii so they tend to produce rain. You can do a rough calculation of the snow level if you know the sea-level temperature. Take the sea-level temperature in Fahrenheit, subtract 32, and divide by 3.3 to get the freezing level in thousands of feet. Since snow takes time to melt, it can snow down to about 1000 feet below the freezing level. Which means that if it is 60 degrees like it was in Bothell yesterday it would rain up to about 7500 feet. Not good if you want to ski. Good if you want to go running in the rain. Since the Cascade watersheds are only around 4-6 thousand feet for the reservoirs, and since part of our water storage exists as spring snow, a couple degrees of global warming has the water managers worried.
DeleteDidn't Mr. Trump say several times there's a way to divert all that water to the parched sections of California?? 🤔😵💫
ReplyDeleteSki prospects for WA improving next week when colder air (as seen on todays extended 850mb charts) moves in starting ~tues 12/16 and especially later next week. Accumulated snowfall around Mt.Rainier showing 60" totals by 12/20 most of it falling later next week. While that's exciting we must remember what one of the NWS SEA forecasters (?Felton) said years ago... "the mrf givith and the mrf taketh away"...
ReplyDelete🙏🙏✨
DeleteSo when does Act II begin? Do I need to go buy my extra big bag of popcorn now, or can it wait?🤔
ReplyDeleteBut why this gigantic rain shadow over the North Sound? With wind from the WSW, there should be a convergence zone... Tell me why I'm wrong.
ReplyDeleteWell here's a pile of bunk from today's S Times Climate Lab (brace yourselves for this):
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"These are temperatures that would be rare or almost impossible at this time of year without the influence of climate change, Winkley said.
“As we continue to warm the planet through pumping heat trapping pollution into the atmosphere, these very normal rain events due to atmospheric rivers have a very good potential of becoming even more inconvenient or more detrimental,” Winkley said."
Then, a few lines after that:
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"To say we need the moisture would be an understatement.
So, by and large, this much rainfall is a welcome development. But it’s by no means a magical end to our water woes.
At the moment, nearly every square inch of Washington remains abnormally dry, according to the U.S. Drought Monitor. The central portion of the state sits in “severe” drought while the southeast corner suffers from “extreme” drought.
The state’s reservoirs are typically low this time of year but even so, they’re exceptionally low, said Caroline Mellor, the Department of Ecology’s drought coordinator. The five reservoirs within the Yakima River basin sit at less than two thirds their normal levels for mid December.
Any and all moisture is good news, Mellor said. But because it’s falling as rain we can’t capture as much as we’d like.
And as the atmosphere warms more, the Pacific Northwest is increasingly expecting to see more of its precipitation as rainfall rather than snow.
Most reservoir operators only fill their systems so much this early in the season, leaving plenty of room for water in case of extreme weather, and to ward off the potential for widespread flooding. Once the reservoirs hit their flood-control levels, any rainfall that follows must flow out to the ocean.
What this state needs now more than rain, Mellor said, is snowfall. But temperatures aren’t cold enough to freeze the precipitation across the lower elevations. If the trend continues, these atmospheric rivers will represent a giant lost opportunity as we watch much of their water flow into Puget Sound.
It’s early in the season yet but already the state sits at less than half its normal snowpack level, Mellor said.
Snowpack on some peaks in the Olympics or Cascades still sit completely barren or in the single-digit percentages. Unless that white fluffy stuff starts building up fast and remains until late in the spring, we run the risk of yet another drought in the year ahead."
From today's ST climate lab - have a good laugh as you read this:
ReplyDelete"To say we need the moisture would be an understatement.
So, by and large, this much rainfall is a welcome development. But it’s by no means a magical end to our water woes.
At the moment, nearly every square inch of Washington remains abnormally dry, according to the U.S. Drought Monitor. The central portion of the state sits in “severe” drought while the southeast corner suffers from “extreme” drought.
The state’s reservoirs are typically low this time of year but even so, they’re exceptionally low, said Caroline Mellor, the Department of Ecology’s drought coordinator. The five reservoirs within the Yakima River basin sit at less than two thirds their normal levels for mid December.
Any and all moisture is good news, Mellor said. But because it’s falling as rain we can’t capture as much as we’d like.
And as the atmosphere warms more, the Pacific Northwest is increasingly expecting to see more of its precipitation as rainfall rather than snow.
Most reservoir operators only fill their systems so much this early in the season, leaving plenty of room for water in case of extreme weather, and to ward off the potential for widespread flooding. Once the reservoirs hit their flood-control levels, any rainfall that follows must flow out to the ocean.
What this state needs now more than rain, Mellor said, is snowfall. But temperatures aren’t cold enough to freeze the precipitation across the lower elevations. If the trend continues, these atmospheric rivers will represent a giant lost opportunity as we watch much of their water flow into Puget Sound.
It’s early in the season yet but already the state sits at less than half its normal snowpack level, Mellor said.
Snowpack on some peaks in the Olympics or Cascades still sit completely barren or in the single-digit percentages. Unless that white fluffy stuff starts building up fast and remains until late in the spring, we run the risk of yet another drought in the year ahead."
With 2.28” of rain, KBLI recorded its 15th wettest day on record on 12/10 and the wettest day since 11/14/2021. It was the 2nd wettest December day on record after only 12/30/1979.
ReplyDeleteThis is great information, thank you. Is there a way to subscribe to this feed for updated info? I dont see an RSS link anywhere but I think Google killed that anyway.
ReplyDelete