12:30 pm Wednesday…
Here are the highlights…
WE ARE CONFIDENT WITH THIS:
- Most of us will see regular rain arriving between 11am and 1pm tomorrow.
- Anyone above 1,000′ will definitely see rain only. It’s warmer higher up.
- It only takes 5 minutes of freezing rain to turn a dry road into an ice rink.
- The morning commute should be dry. But spots of freezing fog again where skies clear this evening and fog redevelops.
- The evening commute should be fine, with rain showers and temps 35-40.
- The central/eastern Gorge won’t thaw until evening, that includes anywhere east of Multnomah Falls.
TIMING IS EVERYTHING TOMORROW:
- To get freezing rain to “freeze” on pavement, the air temperature needs to be about 28-30 degrees or lower during the daytime. Even at night, to get roads iced over, it needs to be down around 30-31. Most spots will be at that temp or warmer at 11am-1pm, thus the reason I think most of us west of the Cascades will not see traffic issues.
- IF THE RAIN ARRIVES BEFORE 10 AM, MORE WIDESPREAD FREEZING RAIN IS POSSIBLE! Tomorrow is definitely a “watch the radar” day.
- If the rain waits until noon-1pm, none of us westside should get freezing rain.
So what has changed since I posted about this event yesterday?
Not much, but I’m being a bit more cautious. It IS warming up dramatically above 1,500′ today. I see some 50 degree temps in the foothills of the Cascades and the KPTV Tower temp keeps rising. Thanks to Jim Little for this graph:
In the lowest elevations we had a round of freezing fog last night with the cold air trapped below an inversion; a common occurrence in wintertime here. I was really surprised a few districts in the metro area cancelled classes based on freezing fog! I’ve never seen that. Both Portland and Vancouver did so, although none did in Washington County or Clackamas County. And Portland was the only district to close in Multnomah County.
Skies are clearing in some spots, mainly where some east wind from the Gorge is drying things out. Just a little mixing going on, I’m seeing temps getting close to 40 in parts of Washington County and near the Gorge. Other than those “warm” temps, no changes through this evening. It’ll be another mainly clear and cold night with spots of freezing fog developing. Areas that don’t clear out today will just sit under low clouds/fog tonight.
So obviously that sets us up for possible freezing rain Thursday morning if the precipitation arrives early enough. Models are still insistent on nothing before 10-11am. They have been very consistent for quite a few runs. That includes the new 18z NAM and 18z RPM. There won’t be ANY mild mixing wind before the precipitation arrives, so that won’t help at all.
As a result it comes down to an epic race between the rising temperature and the incoming rain tomorrow morning/midday. The best chance for freezing rain may be the calm pockets in Washington, Columbia, and Clark counties. Areas near the Columbia River Gorge in the metro area might have the LEAST chance because of the mixing east wind going tonight keeping temps up. Just a guess. Our RPM even shows a few spots in western Washington County as the precip shows up around 10am:
The east wind in the Gorge will be dying quickly tomorrow, so I think it’s most likely we’ll only see freezing rain east of Multnomah Falls, assuming the rain waits until 11am or later to show up. It’s possible the freeway will be mainly clear if temps rise above 30. But I do not expect a widespread and dramatic warming during the afternoon, thus some ice accumulation is likely at Stevenson, Hood River, and maybe The Dalles.
Chief Meteorologist Mark Nelsen