Coldest night of the year for many of us tonight

Quite a change today! All sunny in the metro area and much of the Willamette Valley, but cold/dry modified arctic air has flooded into the Pacific Northwest. This will remain in place through tomorrow, and to a lesser extent Thursday too. We struggled into the mid-upper 30s in the metro area. Portland’s high of 37 was the coldest since New Year’s Day, but not a record cold high temp for the date.

Notice it wasn’t quite as cold away from the Gorge. But very cold in Central Oregon! Teens there after a weekend in the upper 50s to 60.

Dewpoints have dropped down to around 10 in the metro area. The current value of 8 means it’s the driest airmass we’ve seen in 2.5 years in the metro area. We had an early season “arctic blast” back in late October 2019 that brought dewpoints down below 5 degrees in Portland. That’s skin-cracking dry! When the air is this dry, and wind is calm, the temperature can drop WAY down at night.

Easterly wind has backed off a little this evening, and I expect calm conditions by sunrise for about 1/2 of the metro area. We KNOW it’ll be cold everywhere tonight. In the windy areas (Troutdale, Camas, Gresham, Parkrose etc...) temperatures will “only” get down to 25-27 degrees. Then the spots that go completely calm should drop down into the teens. Maybe as low as 15 in the coldest outlying areas. The low temperatures so far this winter

It seems reasonable that the wind should at least go briefly calm at PDX airport tonight, allowing temps down into the lower 20s. We’re going for 22 at that location and this should be the coldest night of this cold spell. That’s because a few clouds show up tomorrow night, then the airmass warms after tomorrow

IF we make it below 23, it’ll be the coldest temperature in Portland since the February 2014 cold snap. That one involved a very cold Gorge wind plus snow.

Tomorrow should be great with sunshine once again, but east wind backing off. Much calmer conditions for many of us. I’m watching Thursday morning closely since a disturbance dropping down out of Canada could give us flurries. Some models are totally dry, others produce those flurries. At this point there’s no indication that we could even get 1/2″. There’s a very good chance we just stay dry. The evening GRAF model keeps trying for flurries at 7am Thursday