9:30pm: Looking Wetter & More Damaging

January 6, 2017

(All forecast points are still valid from this afternoon’s posting down below)

All the evening models are in, except the ECMWF.

They all show an ominous trend with the precipitation…wetter Saturday night and Sunday.  Our RPM is often a bit too wet, but you get the point with the total forecast of more than 1″ of liquid water ending Sunday at 4pm.

rpm_12km_precip_nwor

Remember that I think we’ll be BELOW FREEZING through the daylight hours Sunday.  This would say we get a widespread 1″ of glaze ice on metro area trees & powerlines.  Very bad.  Other evening models look similar:

NAM-MM5: .90″
WRF-GFS: 1.00″
NAM: 1.30″

If this is the case then that means a good chunk of the metro area could see a devastating ice storm Saturday night through Sunday afternoon.  Hmmm, I might have to take advantage of “Casa-KPTV” this weekend…

Two other things going on tonight that reinforce my belief that we’re locked in sub-freezing air all through Sunday.

  1. No evening model pushes in southerly wind or gets rid of the east wind until around sunset Sunday at the earliest, as a cold front passes by overhead.
  2. The airmass flowing through the Gorge is ALMOST as cold as the January 2004 event.  Down to 24 at PDX and TTD, and 18-20 at Corbett.  This is BEFORE we get a drop in temps from evaporational cooling.  It’s pretty obvious we’ll stay closer to 25 through most of tomorrow at PDX.  Brrrr!

Speaking of the wind, it is RAGING out there in the Gorge.  Gusts 60-70 mph in the Corbett area with windchill beginning to drop below zero.  Hold on!  You’ve got just 48 hours to go until it goes calm.  But it’s going to be a very long 48 hours.

Chief Meteorologist Mark Nelsen


Winter Storm Warning: Here Comes The Snow & Ice

January 6, 2017

4pm Friday…

Wow, I just drove by the Freddie’s gas station; it looked like maybe Armageddon is upon us.  But don’t worry, it’s just another Snow-Icemageddon instead.  Our lives will continue on at some point after Sunday.

Confidence is now quite high that we have another snow/ice event on the way.  At least this time it’s on the weekend, so load up your Netflix queue and stack up that Amazon watchlist, and of course keep us tuned in here at FOX12 too.  I’ll be here until further notice…at your service.  Take a look at the map…almost all of Oregon covered by Winter Storm Warnings and Winter Weather Advisories…

markwarnings_winter-wx-advisory

 

 

PORTLAND/VANCOUVER METRO HIGHLIGHTS

A Winter Storm Warning is in effect for Saturday for much of our viewing area west of the Cascades.  This storm also affects Eastern Oregon of course.

  • One more mainly clear and cold night.  Strong and cold Gorge wind picks up and spreads across much of the metro area by sunrise…brrrr!
  • Snow flurries arrive between 8-10am, with steadier snow arriving by noon at the latest.  Get your errands done this evening or VERY early tomorrow to be safe.
  • I expect a Trace-2″ snow before a changeover to ice pellets and then freezing rain around sunset (4:45pm) “Deepest” snow likely west and south metro, lightest north (Clark Co.) & east
  • Then freezing rain is the precipitation type through Sunday evening.
  • For much of the metro area, this means an ice storm begins Saturday evening and continues through Sunday evening as the cold east wind continues to blow.  Expect 1/2 to 1″ ice accumulation which will bring down trees/limbs/powerlines.
  • I don’t expect temperatures to go above freezing in the metro area until Sunday night.
  • A slow thaw (no real warm south wind) begins after sunset Sunday and continues through midday Monday.  Many roads will still see lots of ice leftover even on Monday AM.

IMPORTANT NOTES FOR THE METRO AREA

  1. Finish your traveling and errands (anything else that involves moving around on roads) this evening or very early Saturday AM.
  2. All roads will be frozen all day tomorrow and most of them stay frozen Sunday.  ODOT says they may finally be using salt in specific trouble spots on freeways from what I hear, so it’ll be interesting to see if it’s effective during freezing rain.  By Monday afternoon I think main roads should be back to normal for most parts of the metro area.
  3. Probably still lots of school closures Monday AM

WILLAMETTE VALLEY FROM LONGVIEW TO EUGENE

The same general plan with snow to freezing rain tomorrow.  Parts of the valley could see up to 3″ of snow, but I think Trace-2″ is most likely a good average number, lightest to the north around Longview.  Then freezing rain through at least Sunday midday.  Expect up to 3/4″ ice accumulation by midday Sunday.  This could be a damaging ice storm for many of you.  The valley will warm up above freezing probably Sunday evening a bit quicker than here in Portland.  Then the event will finally be over.

OREGON and SW WASHINGTON COAST

Temps will be slow to warm, but WILL eventually go above freezing by Saturday evening.  So expect a Trace to 2″ snow by afternoon, then a wintry mix of ice pellets to freezing rain the rest of the day turning to rain by evening.  The coastline should be all above freezing later tomorrow night through Sunday.

COLUMBIA RIVER GORGE

As always, this area is the biggest problem because it’s the meeting ground of the Pacific moisture and cold eastside temps.  It’s the only place between Canada and California where that happens.  The midday/afternoon snow will be accompanied by the usual blizzard-like conditions at the west end due to the strong wind.  By tomorrow evening the far west end (Corbett/Washougal) will transition to freezing rain like the rest of the metro area, but the east end stays as snow through midday Sunday in the deeper cold pool.  The wind ends Sunday evening, but I don’t see a warming west wind; your snow isn’t going anywhere afterward for Monday/Tuesday.  Expect a total of 6-10″ at the east end, and a big ice storm again at the west end.  There will be some thawing Monday at the far west end.  A second, even wetter storm arrives at some point Tuesday and goes into Wednesday as the cold east wind returns.  This could be a real whopper with heavy snow east and snow or freezing rain west end.  Details uncertain on this one 4 days out, but prepare for an extended period of difficult travel in the Gorge Saturday-Wednesday.

CENTRAL & NE OREGON

More snow…but at least instead of 0 to -10 it’ll be more like 10-25 degrees.  Expect severe blowing snow and blizzardlike conditions again on I-84 through the Blue Mountains and Ladd Canyon.  The Grand Ronde and Baker Valleys will be a mess with the blowing snow.  All areas get at least 2″ out of the storm, but many higher mountains will see 6″ or more.




Discussion:

Whew, lots of weather in the next 5 days!  I feel pretty good about the forecast for the weekend; quite good agreement among the different models on the sequence of events.  Plus we’ve been through almost this exact situation many times in the past.  A few key meteorological points:

  1. Easterly flow increases through the Gorge and reaches a peak late Saturday night and Sunday AM at the same time it’s pouring in the metro area.  Perfect setup for a big ice storm.  That easterly flow doesn’t go calm until Sunday evening when a strong cold front passes overhead.
  2. Snow levels peak around 5,000′ or so WEST of the Cascade crest Saturday night too = high confidence for all liquid in P-Town tomorrow evening through Sunday.  Of course east of the crest the cold air banked up eastside means snow makes it all the way down to the Columbia River in the Gorge.
  3. The transition Sunday night is interesting.  We’ll be going from the “cold surface flow from the east wind+warm air overhead” setup, to a “well-mixed hilltop-snow type pattern with light southwest wind”.  By Monday AM the snow level is back down around 1,500-2,000′.  This will help mix out the very cold air at the surface, but my gut feeling is that we won’t have a sudden warming southerly wind Sunday evening.  Instead temperatures will just gradually creep above freezing overnight in the metro area and we’ll be sitting in the 35-40 degree range for the Monday AM commute.  That ice is going to be quite slow to melt.
  4. There is no real westerly wind in the Gorge the next 5 days.  The cold easterly flow returns (although far more shallow and with much higher dewpoints) Tuesday or Tuesday night.

Cold arctic air stays in southern Canada and northern Washington all of next week.  At the same time wet systems are moving into California and Oregon with the polar jet stream pushed farther south than normal.  This keeps the risk of interaction between the two airmasses going for a while.   A particularly wet one moves right over our forecast area Tuesday and early Wednesday.  This has the potential to bring snow or freezing rain to low elevations again close to the Gorge and areas north.  But the ECMWF is bringing the storm farther north, which would keep the metro area too warm.  This is still 4-5 days away and AFTER this current event…but just something to keep an eye on.  I’m feeling pretty confident that the next 5-6 days could be somewhat historic for snow/ice in the Columbia River Gorge though.

Chief Meteorologist Mark Nelsen