Wed Weather Blog

February 6, 2019

5:30pm Wednesday…

I’ve mentioned in the past week that we’re in an unusually cold period through at least Valentine’s Day.  And we’ve known there would be multiple chances for low elevation snow.  It looks like this weekend will be one of those and there’s a pretty good chance it’ll affect your travel.

First, I’ll dial back the weather drama.  This time unfortunately it’s coming not just from other news organizations but a local weather source or two as well.  Because models always do so poorly with snow total forecasting well ahead of time, as meteorologists we typically don’t give specific snow forecasts until about 2 days out.   For example for this last snow event, at one point 4 days ahead of time some models were showing 4-6″!  Luckily I didn’t jump on that (shoot a graphic out to Twitter) and once we got within two days of the event we started giving you that general Trace to 2″ forecast.  To summarize, we don’t yet know if this will be just a light snow event with an inch or two on Saturday & Saturday night or does Portland turn into a snowy, cold, hell with 5″ on the ground by evening.  It’s too early and models disagree, so anyone telling you exactly how much snow is going to fall Saturday is either making a little Click-Bait or being a bit irresponsible.  No one knows yet how much snow is going to fall (or not fall) on Saturday.

But we all have lives to plan right?  That includes me, so…

HERE’S WHAT WE DO KNOW

  1. There’s a good chance, from the Portland metro area north into Washington, snow starts sticking at some point Saturday and we get a snow storm as a cold system drops down the coastline.  By late in the day, cold Gorge wind will likely begin to freeze up roads/streets.  It’s too early to know if that’s just central/east metro closer to Gorge or if the entire metro area freezes up quickly in the afternoon.
  2. You may need to alter your plans for the 2nd half of Saturday and into Sunday because…
  3. Models are all consistent showing that cold Gorge wind spreading over entire metro area by Sunday morning and freezing solid whatever falls (regardless of snow amount).  Sunday we likely stay frozen, thus altering your travel plans for that day too
  4. There will likely be another snow event sometime between Sunday night and Tuesday; each model is VERY different at this point.  Some say very little and slightly too warm, others give us a ton of snow.
  5. The Columbia River Gorge, westside elevations above 1,000′, and Cowlitz/Columbia counties north are in the “snow business” from Friday night until further notice.   Friday night through early next week have the potential of bringing MANY inches of snow in those areas.

WHAT WE DON’T KNOW YET

  1. How much snow will fall Saturday…just an inch? or a real Portland snowstorm with many inches and a cold east wind drifting that around?  No one knows yet
  2. Exactly when roads in the lowest elevations could freeze up Saturday, or does it just wait until Saturday evening when colder east wind arrives?  We’ve got two more days to figure that out.
  3. Details about what happens beyond Sunday.  Some models are mainly dry, others bring a big slug of snow in for Monday morning’s commute.  Others say no real snow until Monday night.  One says slightly too warm with mild southerly breeze Monday midday through Tuesday afternoon in much of metro area (ECMWF).

WHAT’S AHEAD THURSDAY & FRIDAY

Should be uneventful west of the Cascades in the lowlands, although light flurries could drop a dusting if they show up Friday morning.  Temps rise above freezing Friday = roads should be all clear even if there is a dusting somewhere in the morning

FRIDAY NIGHT & EARLY SATURDAY

We’re back into the “snow showers into the hills” setup from Portland metro south and at the beaches.  I think (at this point) it’s unlikely we wake up to a frozen Saturday morning with widespread sticking snow in the metro area.  Only one model is showing that.  Tomorrow we should have a much better idea what’s ahead for this weekend

FOR THE WEATHER GEEKS

As another surge of cold arctic air drops into the Pacific Northwest Friday night through Sunday, the setup appears to be just about perfect for a snow storm somewhere between Puget Sound and Salem (and along the coastline).  Growing up in this area, watching the weather all those years, and attending the UW, I’ve always known a surface low dropping down the coastline with cold high pressure to the north and east IS the snowstorm setup for us.  That’s what ALL models show during this period…no disagreement.  See the slideshow.

But everything has to be just right to get that snowstorm (including lots of precipitation).  The WRF-GFS is fastest with the cold air, converting us from “snow in the hills” Friday night to “snow to valley floor” right away Saturday morning.  I’m trusting the ECMWF/NAM/GFS with the slower arrival of cold air, both from the wrap-around stuff coming onshore and east wind through the Gorge; they did much better this last time.  Although even that WRF shows the dreaded “warm tongue” of southerly flow keeping snow off the valley floor through Saturday afternoon (and just fine road conditions) in west metro, & south/southeast metro.  This says only east wind areas get decent snow during the day.  Of course that includes Clark County and north of Tillamook along the coast.

wrf_4km_Friday4pmtoSaturday4pmsnow

ALL models show the cold air surging in from the east by evening.  Snowfall by 10pm Saturday from the GFS, an even slower arrival of cold east wind, only a dusting to 1″ in the entire metro area.

gfs_10pmSatSnowTotal

ECMWF seems reasonable changing us over to sticking snow the 2nd half of Saturday.  By 10pm Saturday it’s giving us 1-4″ as we’re totally frozen with a strong east wind blowing.  Again, you see that very little falls south of Wilsonville in the Valley.  In general the ECMWF just isn’t as “wet” as other models, thus the lower totals up in S.W. Washington

ecmwf_24hrsnow_10pmSaturday

That’s enough for now…dinner time!  I’ll be working most (or all) days between now and the latter part of next week.  I’ll be keeping a close eye on things as they develop.  Now if/when I really do see a snowstorm?  Then you’ll see more colored text, big fonts, and excessive tweets/Facebook posts.  Otherwise I’ll keep it to all info and no hype.

Chief Meteorologist Mark Nelsen

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