Quick Evening Snow Update

February 19, 2018

9:45pm Monday

All evening models except ECMWF are in.  A few additional thoughts, although make sure you read the HIGHLIGHTS section on the previous post.

  1. Only the WRF-GFS and RPM give us little or no snow.  They are quite dry showing almost no precip…thus little/no snow.
  2. All other models give us an inch or so to as much as 5-6″.  Confidence has grown that we’ll have some sort of widespread coverage of 1-2″ at least.  This will likely be the most widespread snow event of the winter.  It should also be the first snow in the Willamette Valley south of the metro area.  Here are the latest numbers (ECMWF is from this morning).

Snow Model Accumulation Several

3. Wind is light much of the day, then east wind starts pouring out of the Gorge in the evening as the low pressure moves by offshore.  It’s not a big mid-winter type strong easterly wind, but enough to transport dry air over us.  That helps drop us to freezing and below during the evening/overnight hours.

Of course the huge question is about the evening commute.  I think whenever the heavier snow decides to show up, that’s when things may grind to a halt within an hour or so.  And we’re not confident on that timing.  Our freeways are over-capacity for the population that lives here.  So I think we all know it won’t take long to bring things to a halt.  You see the BEST CASE and WORST CASE scenarios below.  I’m inclined to think this might be like the January event last year where much of the commute was okay (wet)  but then things ground to a halt right around 6:30-7:00pm.  The really bad event last year (December 14th) was when the snow showed up on already-frozen roads at 2-3pm.  I think that is unlikely tomorrow.  The heavy snowfall appears to show up well after 4pm.

Mark Road Condition Forecast

Snow Cold Look Ahead Forecast 2

So tomorrow is a day to keep a close eye on radar (hopefully it doesn’t break down) and temperatures.  I’ll be on at 5, 6, 8 (FOX12 PLUS) , 9 (FOX12 PLUS), 10, & 11…shouldn’t be hard to find me!

Chief Meteorologist Mark Nelsen


Widespread Snow Likely Tuesday Evening & Night

February 19, 2018

2:00pm Monday…

Last night the clouds didn’t clear out as expected so we just dropped to freezing or a bit below in the metro area.  Lots of icy streets but it appears it wasn’t a total ice-pocalypse for the morning commute.

Today we’re under a dry flow of air from the north which is giving us lots of sunshine but chilly temps…a good 10 degrees below average.  We’ll end up around 40 or so.

We have an almost perfect sticking snow setup for the lowlands with two disturbances coming straight down from the north the next 3 days.  They pick up a bit of moisture once they move over the coastal waters offshore, then generate snowfall in mainly Western Oregon and SW Washington.  The one issue (if you want lots of snow) is that it’s late February and daytime heating is “strong” for late winter.   This DOES keep us from having an all-day snow/ice event where roads stay frozen…you know, continuous-coverage type snow event for TV folks.  Roads just don’t stay frozen/icy the whole day this time of year…whew!

I see two good chances for lowland snow before a slight warm up Friday night and into the weekend lifts sticking snow levels back up into the foothills.  1st is tomorrow afternoon through early Wednesday morning, the 2nd is early Thursday morning.

We have a big problem forecasting how much snow we get tomorrow afternoon through early Wednesday…models have widely varying snow totals and also put the heavier stuff in different places.  Check out 7 different models showing total snow accumulation by 4am Wednesday.  Blue on most of them is 2″ (or more). See the issue?  You can click on each individually for a larger view.

The big message here is that SOME AREAS BETWEEN OLYMPIA AND EUGENE SHOULD GET A GOOD 2″ OR MORE SNOWFALL BY WEDNESDAY AM.  But SOME AREAS WILL ONLY GET A DUSTING TO 1/2″.  Each model is slightly different in the placement of precipitation.  Note the one that shows 4-6″ snow centered on metro area.

If this was all rain none of you would notice; we’d just forecast increasing rain showers Tuesday afternoon through Tuesday night.  Would any of us care if we got .05″ rain instead of .30″?  Nope!  We wouldn’t even notice, it would just be a little wet.  But when that falls in the form of snow that’s the difference between a dusting and 3″!  Suddenly it matters!  You see the forecast problem now don’t you?

But I get paid to make a forecast and prepare you for the possibilities, so here’s what I’m thinking this afternoon:

  1. Light snow showers develop most areas west of the Cascades tomorrow afternoon, then pick up in intensity after 6pm or so.
  2. Temperatures likely hover near/above freezing through early evening, so MOST LIKELY roads will be mainly wet through the evening commute.
  3. Dropping temps and increasing snowfall should turn many roads snowy by late evening.  No, we don’t know exactly when; it depends on snow intensity and how warm it gets during the daytime.
  4. Expect 1/2″ to 3″ in the western lowlands from Longview to Eugene.
  5. Many roads/areas will have fresh snow on the ground for Wednesday AM commute, then thaw during the day (travel just fine during day).  Wednesday may be a Snow Day for many areas west of the Cascades.

 

COULD TUESDAY EVENING’S COMMUTE TURN INTO A HELLISH EVENING WITH TRUCKS & CARS STUCK ON FREEWAYS…LIKE LAST WINTER?

YES,  That is a “worst-case” scenario at this point, not likely but possible.  If snow starts falling heavily during the evening commute, temps could immediately drop to 32 degrees and we could have a fiasco.  How to avoid?

  • EVERYONE should have chains, studded tires, and/or 4 wheel drive vehicle available for use tomorrow evening just in case this happens.  Otherwise please don’t get on roads/highways if they turn snowy.
  • Hopefully transportation agencies have learned quite a bit from last year.  For example I would hope salt is in place to keep interchanges, ramps, & bridges clear this time.  (personal opinion ahead)… The de-icer used in the past doesn’t seem to do much; in both storms last year highways just froze up.  Why do we soak our highways in thousands of gallons of chemical if it freezes anyway? …(end opinion) Remember some of you stuck at I-84/I-5 interchange for 6 hours?  Same on approaches to Marquam Bridge and Sylvan Hill.  Bad memories we don’t need to repeat…

 

WHAT ABOUT SCHOOLS TOMORROW?

With a little daytime heating I think we’re fine until sunset in most lowland locations.  But administrators should be keeping a close eye on noon/early PM temperatures and radar.  I’ll be doing the same.

COAST?

Snow showers all day tomorrow.  Not much stickage since temps will be above freezing, but after dark maybe a little on roads.  I could see a Trace to 1″ anywhere along the coastline, with more in the Coast Range of course.

GORGE?

Same as western lowlands, although drier in the eastern Gorge, farther removed from moisture.

That’s the update for now, of course I’ll be keeping a close eye on things in case for some reason timing suddenly speeds up (morning snow!) or models turn much heavier with the snowfall.

Good times ahead!

Chief Meteorologist Mark Nelsen