Gorge Snow

Today's quiet weather provided a good day for the Portland NWS folks to host local TV weather people for a GOES-17/GOES-WEST training session.

Capture

That satellite was just declared OPERATIONAL yesterday.  It has some minor issues, but in general it’s a big leap forward in technology.  You can read more about it here:

https://www.noaa.gov/media-release/latest-weather-satellite-will-improve-forecasts-for-western-us-alaska-hawaii

A surface low pressure system moves north out of California tomorrow, crossing almost directly over Portland in the afternoon.  As it approaches, it is once again pulling cold air from Eastern Washington down into northeast Oregon and the Columbia River Gorge.  You can see the cold colors (strong surface high pressure) nosing down into the state on this WRF-GFS surface pressure map for 7am Thursday

or_slp.27.0000

The HRRR shows the problem with temps well below freezing by morning in central/eastern Gorge.  Notice it shouldn’t be cold enough for freezing rain in the metro area, including Troutdale/Camas/Washougal

HRRR Rain_Snow

The result is that it’ll be cold enough for snowfall from around Multnomah Falls eastward.  Should be enough moisture for 4-8″ new snow.  I’m leaning toward the lower end of that forecast

Mark Warnings Winter Weather Lowlands

Where the cold air is a bit thinner in southern Wasco, Sherman, & Gilliam counties there will be spots of freezing rain for a few hours morning/midday.

In the far western Gorge the big question is…will temps be cold enough at Corbett, Crown Pt, Mt. Pleasant, and Cape Horn for freezing rain?  I think so.  At least above about 500′.  Close call.  It shouldn’t be a big freezing rain storm, but we’ve only seen a trace a couple of times so far this season.  It should be a bit more this time, maybe a quarter-inch of ice accumulation.  That’s not enough for damage, but enough to turn roads icy in the morning for some school districts

Mark Warnings Winter Weather Lowlands2

By the way, here are the latest snow totals from the eastern Gorge from CoCoRAHS.  Hood River Valley has seen around 20″ or so.  Just above White Salmon almost 3 feet, and of course the snowy climate of Trout Lake hasn’t disappointed.  About 4 feet of snow in 3 days up at that 1,900′ elevation.  The long-term average winter snowfall is about 100″ in that location compared to Portland’s 5″ average.  Hood River averages somewhere between 20-30″ per winter.

Snow Totals Gorge

Looking farther ahead it’s obvious February will end up a very chilly month.  We’re going to stay in a cool pattern for at least the next 10 days.  Persistent upper-level ridging remains in the Gulf of Alaska and occasionally allows cold upper-level troughs to come down the back side…into the western USA and SW Canada.  The 240 hour GFS and GEM ensembles show such a cold trough right over us for the last weekend of February

Snow levels will remain low and snowpack will continue to build in the Cascades.  And don’t count on any “false spring” weather with highs in the lower 60s anytime in the next 10 days.

Chief Meteorologist Mark Nelsen

Chief meteorologist

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