A chilly airmass is still sitting over Eastern Oregon below about 4,000′. That cold pool of air continues to feed a gusty east wind through the Gorge. You can see it in the cool colors on the 925mb WRF-GFS map:
The pressure gradient from The Dalles to Portland was up around 10 millibars earlier yesterday, but it’s down to around 7 right now. The pressure difference directly impacts the wind speed out there. This chart reads from right to left
Temperatures are within a few degrees of freezing from the Corbett & Mt. Pleasant areas in the western Gorge all the way to The Dalles. So right now we are maybe 5 degrees colder than last week when we saw a dusting of snow above 500′ or so east of Cascade Locks.
Tonight and most of the daylight hours Wednesday we’ll be dry as a dying system moves overhead. Sure, a few sprinkles west of the Cascades and a few flurries in the central/eastern Gorge, but that will be about it.
Tomorrow evening and night a wet system moves overhead. The flow of cold air will actually INCREASE as a deep low pressure area moves towards the coastline; the strongest east wind of this event will be the result in and near the western Gorge. At the same time precipitation arrives around sunset or just beyond and falls through that cold airmass. It appears now that it’ll be mainly snow from around Bonneville Dam eastward. A thinner layer of cold air from there to Corbett/Cape Horn areas means freezing rain & ice pellets are likely in the western Gorge.
There is not a huge amount of moisture available for a big snow/ice storm, but the best we’ve seen so far this season. That doesn’t say much this year! Here’s what I expect:
- Roads may turn icy in these areas anytime after sunset Wednesday, soon after steady precipitation arrives.
- I-84 will likely remain bare through this event up to at least Multnomah Falls. Expect snow on the freeway (or at least slush) for the Thursday morning commute east of there to The Dalles. By midday Thursday and beyond, the freeway should be clear since temperatures are not starting out as cold as they could be.
- Expect some school closures/delays in the Columbia River Gorge Thursday morning
- Additional precipitation later Thursday may fall as freezing rain in the Hood River and White Salmon valleys, but I doubt it’ll be cold enough for river-level highways (I-84 and SR14) to freeze up again.
- Expect a cold and windy night in central/east metro Wednesday night, but temperatures remain in the upper 30s, no freezing rain or snow.
Chief Meteorologist Mark Nelsen