Wednesday, February 8, 2017

Northwest WA Snow, the Big Warm Up, and Flooding

Today, while much of western Washington warmed and was hit by moderate rain associated with a warm front, Northwest Washington, stretching from Whatcom County to San Juans, experienced snow.

Why localized snow?  Because of cool air jetting out of the Fraser River Valley northeast of Bellingham, as illustrated by this surface map at 10 AM today (Wednesday).  The Fraser River Valley acts as a conduit of colder air from the interior of British Columbia and the approaching low pressure increased the pressure difference across the gap.
The warm front has brought dramatically warmer temperatures over our region.  Check out the temperatures and winds above Seattle during the past 24 h using a time/height cross section (time is along the x axis, height is the y axis, see below).  Huge warm up from roughly -6C to 3 C at 850 hPa pressure level (about 5000 ft).  About 15F increase. The freezing level at Quillayuate along the WA coast rose to over 8000 ft this afternoon.

The warm southwesterly flow was associated with an atmospheric river, a current of large moisture values out of the tropics (see map of moisture values at 10 PM)
As this moisture ascended our terrain, moderate to heavy rain fell, as shown by the 24h values ending 8 PM.  Particularly heavy rain was found over the southern WA and Oregon Cascades and over the coastal mountains (some places received more than 2 inches).   That moisture is being added to rapidly melting snow at lower elevations.

But it doesn't stop there.  Here is the precipitation total forecast for the next 48h from the UW WRF model.  Wow....5-10 inches over the coastal mountains and the higher Cascades.  California shares the fire hose of water as well.

All this precipitation (and a very high freezing level, rising to over 7000 ft), is causing the regional rivers to rapidly rise, with a number of them at or near flood stage (red dots).

And a combination of high astronomical tides and low pressure could cause coastal flooding.

Did I mention the potential for strong winds mid-day Friday as a strong trough of low pressure moves through our region?

Lots of activity to keep meteorologists busy...but remember, the start of  meteorological spring in the NW is only a few weeks away:  February 25th!
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Announcement

The Northwest Weather Workshop, the big annual weather gathering in the Northwest, will take place on March 3-4, 2017 in Seattle (NOAA Sand Point Facility).   Everyone is welcome.  For more information and to register, go to https://www.atmos.washington.edu/pnww/
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17 comments:

Rod said...

Plus, all three passes (Snoqualmie, Stevens, and White) are now closed. That is rather rare, indeed.

David Riley said...

One question: Will Snoqualmie Pass be pow or concrete on Saturday?

Charles Nathaniel Erwin said...

I noticed that Lake Oroville in California is having some trouble with being too full and a spillway that is failing. Feast or Famine.
https://ww2.kqed.org/news/2017/02/07/engineers-assess-spillway-problem-at-oroville-dam/

Ben Green said...

An inch of snow here along central hood canal before the change to rain earlier today :)

Joel Kawahara said...

California is receiving lots of precipitation. Lake Shasta inflow is 88KAF, the American inflow is 100+KAF, Feather is 85KAF, and even the San Joaquin is running almost 30KAF. They must be begging for the rain to stop.

Reader said...

Checked numerous locations along the I5 corridor between Bellingham and Bakersfield. They are had flood watches or warnings. Indeed much water trying to find a place to go!

Patrick said...

A little off topic, but I just noticed the National Weather Service city report is now in mixed case letters! Goodbye to the teletype era.

Janet said...

In Anacortes, at 65', about 3" of new snow fell yesterday afternoon. Roads throughout Skagit County were slick during the evening commute! Temp was 32-33 F until 1 AM Thursday.

Unknown said...

I wanted to comment on how poor the forecasting has been during the last week here in Bellingham. Of course, we do not blame the NWS for the weather, but their forecasts have been terrible and have consistently underestimated the amount of snow and the persistence of the Frazer River outflow. I am in the southern part of Whatcom County near the airport and even at 8 am, it is still barely above freezing. The temperature turnaround is extremely slow to happen and much later than several predictions.

Weatherfreak said...

Classic post snow pattern morning out there! 11" of snow melting fast, heavy rain and temp up to 47. My back yard is a lake now... Reminds me of when I was a kid growing up on Mercer Is. where a beautiful snow would be quickly washed away with a heavy warm rain the minute the Southerlies kicked in. Yesterday morning we had a nice light snow going and in the time it took me to look down at my phone and back up, it was rain. Life in the lowlands! Looking forward to a decent dry period starting this Sat. with maybe low 50's by Monday. ;)

lhsouthern said...

they are getting ready to close hwy 6 at PeEll/Doty because of flooding

Lori said...

Blasting wind here in Clearview a day early! All the snow is gone with this mornings pouring rain and now 51 deg and sunny!

Mark Allyn said...

I am having trouble finding the Bellingham area on some of your maps. The rainfall map and the river flooding map seem to be cut off just south of Skagit count. Is that intentional or can I blame my browser?

jeff said...

We're having the same issue here in Central Washington, moses lake area. NOAA consistently forcasts a higher temperature than what is observed. For example right now, 9pm, its 19 and dropping and the forcast is for a low of 30. Also forcast is a south wind 15mph w/gusts to 22 and we're observing north @8mph

Mark Allyn said...

I wish to respond to the person commenting about the forecasts for the Bellingham area. I had a conversation with some others who have been in this area for years.

What they tell me is that Whatcom County is notorious for micro climates. An example was on Sunday morning, there was about 1 inch of snow in the Columbia neighborhood. About 10 miles or so north (south Lynden area), there were about 8 inches of snow.

This week, I believe what was happening was that the Fraser outflow was just strong enough to affect only part of the county and perhaps the terrain (hills) may have been enough to block
the wind (which was about 5 miles per hour at times were I lived) that the temperature was right
at the freezing mark. In fact, when I walked from Downtown Bellingham (intersection of Bay and Holly) to my home (at the intersection of E. Victor and Meridian), I notice that there was no ice on light poles in downtown, but lots of ice on lightpoles near my house. And that was a distance of less than 2 miles. I felt no wind in my face walking downtown, but a stead five mile wind in my face near my house.

Perhaps we have to accept the fact the Whatcom will be next to impossible to get an accurate forecast due to it's notorious micro climates.

Vicki Wise said...

It's not really a flooding event unless the cows in the Snoqualmie/Skagit/etc. river valleys are looking for high ground.

Tim said...

It kept on snowing in Eastern Vancouver Island all day yesterday piling up to 60 cm deep!
https://www.cheknews.ca/heavy-snows-hit-parts-east-island-274680/