This cold episode has just about played itself out in the metro area. The cold air layer is quite thin, so I’m thinking it’s going to be tough to get precipitation in the form of snow as all models show warming above about 2,000′ during the night. Most (light) showers should be in the form of sleet (ice pellets) or liquid rain. So of course to get freezing rain you have to get surface temperatures below freezing. Note the current temps:
Thick cloud cover has moved in, stalling metro area temperatures right around the freezing mark. We’re not going to see any significant additional drop.
The flow of cold/dry air out of the Gorge has weakened dramatically. Only 3+ millibars PDX-DLS is not typical ice storm material for us. It’s just a breeze from the east right now even in the usual windy spots; evidence the cold pool is shrinking and turning shallower eastside.
Dewpoints have also risen a bit, so if/when precipitation arrives, temperatures will only fall maybe 1-2 degrees with evaporative cooling.
That means almost none of us drop below 30 degrees. Which leads me to believe that most roads which are thawed right now are unlikely to re-freeze tonight. Freezing rain typically needs air temps down to 30 to get new ice on roads that aren’t already frozen.
- It’s doubtful we see a widespread icing of already-thawed roads in the metro area
- There may be a few new spots of icing, but the main highways/freeways WEST of I-205 and south of Milwaukie/Happy Valley should be clear tomorrow morning.
- Frozen roads in the hills and east metro will remain that way through the morning commute.
We continue the slow thaw tomorrow with almost all roads in decent shape by late afternoon, still some ice east of I-205 though.
South wind arrives Thursday afternoon/night. Until that time no dramatic warmup, just a slow thaw. We should be around 50 by late Thursday evening.
Chief Meteorologist Mark Nelsen