With last night’s slushy snow behind us, all eyes are now on “the big event” for MLK weekend. We’ve been talking about this possibility for almost a week so I’m ready to get on with it.
As we approach a big event like this I like to nail down “what we know” vs. what is still a bit unclear. Luckily we are now highly confident these two weather factors are locked in, but the rest is still a bit unclear.
1) Cold and dry arctic air arrives Friday (probably midday & PM) in the metro area and then spreads westward to the northern Oregon coast and down into the Willamette Valley. That means temperatures FALL on Friday and they may fall dramatically well down into the 20s in the metro area by/after midday…we’ll be freezing up! We assume forecast models are too cold forecasting highs only around 15-20 on Saturday! Portland has not seen a high temperature in the teens in 35 years; that seems unlikely to occur.
2) An unusually strong and possibly damaging east wind will accompany the cold air with gusts 35-50 mph in the West Hills plus central/eastern metro area by Friday night. Everyone will see a gusty east wind, but the really strong gusts will be in the usual areas. Winds gust 70-90 mph in the western Gorge Friday night and Saturday morning, bringing wind chill temps down to around zero or below in the metro area. Power outages when it’s in the 15-25 degree range are no fun.
As for snow, at this point most signs point to at least SOME snow from Longview down to Salem and possibly the far northern Oregon coastline. The rest of the Coast and south of Salem may only see rain switch to freezing rain later Friday. And of course it’ll be all snow in the Cascades and Columbia River Gorge.
KEY POINTS
- Tomorrow is prep day; you should have all pipes wrapped by the end of the day, outdoor water lines turned off, plants protected, flags taken down, etc…
- The NWS has a Winter Storm Watch up for all of NW Oregon and SW Washington. They likely convert that to a warning for some areas as we get closer to Friday. If that occurs, I hope many school districts will cancel classes Friday, even though it’ll just be light rain/snow mixed the first half of the day. A very risky day to have kids on busses in the afternoon.
- Light rain/snow showers Friday morning likely change over to all snow (first east metro, then west/south) and roads freeze up at some point during the day. IF YOU CAN WORK REMOTELY, FRIDAY IS THE DAY TO DO IT! Still, the snow MAY be light Friday afternoon. But wet roads will be freezing up and then even an inch or two of snow on top of that means traffic fiasco.
- A 2nd wave of deeper moisture arrives Saturday and that one dumps quite a bit of snow or freezing rain. Most likely it’ll be snow in the metro area and freezing rain in the valley to the south (Salem/Albany/Eugene). Roads remain frozen and high winds in the metro area would lead to drifting and blowing snow. An ice storm (liquid rain freezing on contact) may cause many power outages in the Willamette Valley.
- Precipitation ends Saturday night and Sunday the sun comes out…but possibly with 2-6″ fresh snowfall in the metro area with a high temperature in the 20s and windchills 0-10 degrees…brrr!
- Wind dies down Monday and Tuesday and we S-L-O-W-L-Y warm above freezing
The setup for Friday and Saturday IS the classic big snow/ice storm setup for NW Oregon and SW Washington. Cold arctic air slides south into the region and then abundant Pacific moisture/precipitation rides over that cold air. We’ve seen it many times, most recently back in December 2022. That event was mainly ice pellets and freezing rain, in this one the cold air should be deeper in the metro area = snow.
The last piece of this wintery mess “puzzle”? How far north/south the main band of precipitation will be as it moves onshore Friday and Saturday determines how much snow we pick up. For several days the GFS model (and its ensemble system) has been pushing much of it over the metro area or even farther north into western Washington. Tons of precipitation but a bit “warm-ish”. Meanwhile the Euro and Canadian models (and their ensembles) have been keeping much of the precipitation aimed at central/southern Oregon, leaving the Portland metro area and points north mainly dry and just cold. They have come together a bit now. Take a look at the 18z Euro ensemble chart for 24 hour precipitation for Portland ending 4pm Saturday. Only 18 of 50 are dry. Far more wet than dry now…didn’t look that way 24 hours ago. That increases the chance for metro snow.
Every single one of those GFS ensemble members are wet (white) for us. Thus our increasing confidence that at least SOME snow is likely for Portland
Our evening GRAF model only generates light snowfall through the evening commute Friday all the way down to around Salem, but too dry up at Astoria and Longview. Again, only 1-2″, but with temps dropped into the 20s would still be a mess on roads
Then the 2nd surge of precipitation Saturday at 2pm as a surface low pressure system moves toward Florence. Notice somewhere north of the metro area gets NO SNOW Saturday. And those temperatures under the precipitation…so cold! Ice storm in progress in the valley.
Now that we’re within 2-3 days of the event, it’s alright to share ice and snow accumulation maps. That’s a mess in the Willamette Valley!
And (remember it’s just one model!) GRAF showing solid snowfall all across metro and Gorge, but little or nothing along coastline (too warm overhead or too dry) and Longview northward (too dry)
That GRAF model has also been pretty good with arctic air the past 2-3 years, but I find it hard to believe we’d stay in the teens all day Saturday with 7″ snowfall. That plus the extremely strong wind would be close to blizzard conditions in the eastern part of the metro area. We’ll assume it’s going to back off on both a bit on future runs.
A big question…could we still avoid a big snowy/icy mess? Yes, if the entire precipitation shield Friday PM and Saturday shifts south 50-100 miles. The metro area would just be very cold, windy, and dry Friday/Saturday. But I feel that’s unlikely at this point. Instead, I think you should prepare for this to be safe. I’ll have more tomorrow.
Copyright 2024 KPTV-KPDX. All rights reserved.