Noon Friday…

It’s rare that we have weather forecasts turn out exactly as expected during these big winter storms. There’s always some sort of “last minute twist” right? Well, so far this event is behaving correctly. But we DO have a last minute twist and that involves freezing rain…lots of it in more places than we were thinking, and that changes our snow total forecast a bit for some of you.

RIGHT NOW

Cold air coming through the Gorge has filled the entire metro area, plus western valleys from Longview all the way down to Albany and Corvallis. Even near/below freezing on the northern Oregon and SW Washington coastline. THIS TEMPERATURE SETUP WILL NOT CHANGE MUCH THROUGH TONIGHT

web_temperature_ORWA.jpg

It appears 1-4″ snow has fallen in the metro area as of 11am. Lighter totals south metro, heavier north and east. Gorge is 3-7″ so far. Official NWS Office total is 1.6″ as of 10am. THE FIRST OFFICIAL SNOWFALL OF THE SEASON IN PORTLAND. Precipitation type has been mainly freezing rain south of the metro area. A pic from the Sloans in Aumsville area…icy

photo sloans aumsville ice.jpeg

What’s ahead? I’ll get straight to the main points:

KEY POINTS

  • Generally we stay frozen from Longview all the way to Salem today. Coldest temps and cold east wind continues through the Gorge. Even at 28-30 degrees roads can partially thaw in the afternoon due to strengthening February sun even through the clouds. Then roads freeze up again after sunset. Expect light snow accumulations central/north metro through sunset, spots of ice pellets and freezing rain south/southwest metro and down into the Willamette Valley. Maybe another 1-3″ in the already snowy areas.
  • Round #2 of much heavier precipitation arrives sometime after sunset and continues until sunrise Saturday. Whatever falls in your neighborhood will be quite heavy. Either thick glazing of ice or lots of snow, or a mix.
  • Expect 4-10″ additional snow anywhere from the central metro area north and east. West metro down through Lake Oswego to Oregon City will see a messy mix of freezing rain, ice pellets, & snow. South of this line, almost all liquid rain that freezes on contact. This is going to be an ice storm to remember in the northern Willamette Valley plus south & west metro. Expect lots of power outages and downed trees…a real mess. Historic.
  • Even in the snowy areas central/east metro there will be some mixing of freezing rain and sleet during the night. Roads will likely be terrible by Saturday morning.
  • From midday Saturday to Sunday afternoon things are pretty quiet. Just light mixed showers (snow, freezing rain, rain) and temperatures rise to around freezing or a little above in the metro area south and west of downtown. Road conditions might improve a bit there. East metro stays mainly frozen through Sunday.
  • Round #3 is Sunday evening and night. Some decent precipitation, although not as heavy as tonight. I think it’s likely much of the metro area south and west of downtown will be near or slightly above freezing and we avoid significant additional ice glazing. But lots of freezing rain in the typical Gorge-exposed areas. That’s central Portland east to the western Gorge, plus the West Hills.
  • Finally, a south wind arrives sometime Monday and cold east wind disappears…into the 40s by afternoon at the latest.
  • EXPECT LOTS OF ICE AND SNOW ON THE GROUND AND IN THE TREES THROUGH THE MONDAY MORNING COMMUTE central and east metro.

TECHNICAL INFO

This is turning into a historic February storm! I’ve never seen an ice storm setup like this so late in the season, but we’ve always known it can happen if everything sets up right. Plus tons of snow…Amazing.

Only minor changes today compared to what I was thinking yesterday, but the “minor change” has a significant effect on snow total forecasting. Basically a warm nose pushes a little farther north into the metro area tonight (we’re talking 10 miles maybe); meaning that what could have been 12″ of snow for some will be 4″ snow + heavy freezing rain instead. Still a huge event, but not as much fun to sled on ice-covered snow. I’m following the WRF-GFS closely for forecast since it’s doing so well. Plus some Euro thrown in since it’s higher resolution than GFS. Surface low up against the coastline right now, keeping cold air in place

wrf_1pmfriday.gif

By 10pm a strong system is approaching the coastline. Cold air is locked in Salem north and surface low is approaching coastline

wrf_10pm.gif

At 7am Saturday the surface low is at Astoria, which means south Willamette Valley may pop into 40s, but below freezing from Salem north

wrf_7amSaturday.gif

How much precipitation has fallen by midday tomorrow? Whew…1.00″ to 1.50″, that’s snow/glaze ice/ice pellets folks. All snow could be 12″, all freezing rain is devastating ice storm

ecmwf-deterministic-portland-total_precip_inch-3239200.png

During the night the warm nose of above freezing air (overhead) shoots north to the Columbia River, reducing snow totals from there to south and west. That zero degree line at 2,500′ is punching north at 3am. Beyond that point it retreats south again.

925_nam3km_3am.png

HRRR produces this much freezing rain

hrrrfreezingrain10amsaturday.png

And WRF-GFS snow total continues to look as it has the past couple of days…4-12″ more snow central/east/north metro

snowby10amSaturday.gif

The morning ECMWF run is similar to past runs as well, thinking we hang on to plenty of snow center and east/north metro

EuroSnow10amSaturday.png

By 7pm tomorrow, the surface low has really beaten down the cold dome east of the Cascades. Wind much calmer in most of metro area but we’re still mainly frozen. Calm wind and not much precip around? I can see some roads thawing (a little) and areas away from the Gorge (and valley) creep up to around freezing Saturday afternoon

wrf_7pmsaturday.gif

Early afternoon Sunday you see another system approaching. It’ll prompt one last big surge of east wind through the Gorge, although cold air will be much thinner in metro area and valley. Notice the 2500′ temp (colors on map) is above freezing for most of the area = mainly liquid precipitation Sunday evening and night.

wrf_1pmsunday.gif

My gut feeling is (based on past storms), west & south metro plus Willamette Valley will be near/above freezing at this point. So no new major ice accumulation there, but this will be the first big glazing from West Hills over to western Gorge. Even the western sections of the Gorge will go to ice pellets and freezing rain at this point.

7am Monday the southerlies are taking over west of the Cascades, but a stubborn area of subfreezing air lingers right along Columbia River and in the Gorge. This happens every time. Since the WRF-GFS was modified a few years ago to better hang on to low-level cold airmasses, it has done a great job.

wrf_7amMonday.gif

Finally, 4pm Monday and southerlies should have even reached Troutdale. But what a mess left behind all across the Portland metro area and Willamette Valley!

wrf_4pmMonday.gif

That’s it for now…

  • We will have specific forecasts for the Coastline, Valley, Longview/Kelso, The Gorge & Cascades all through our evening shows. We are on FOX12 for an hour at 4pm, 5pm, 6pm, 10pm, & a half hour at 11pm. Also two hours on FOX12PLUS 8pm & 9pm. Find me and the weather team there!
  • Make sure you are following me on Facebook at @MARKNELSENWEATHER and Twitter @MARKNELSENKPTV

Chief Meteorologist Mark Nelsen

Copyright 2021 KPTV-KPDX Broadcasting Corporation. All rights reserved. 

Recommended for you

Load comments