Looking Colder…

October 8, 2009

snapshotLots of sunshine again today with temps finally reaching 70 degrees.  So I suppose if we actually would have seen offshore flow this week (remember that was the initial plan about 6 days ago), temps in the mid 70s should have been doable.  But the warm 70 temps will soon be a memory won’t they?

Not much has changed in the somewhat historic cold snap coming this weekend.  Arctic air is pouring west of the Continental Divide this evening…one would think it’s winter with temps in the Flathead Valley heading down into the teens overnight with snow.  This is the first surge of chilly air;  the leading edges of it come through the Columbia River Gorge tomorrow afternoon/evening.  Then a strong upper-level shortwave rotates south from west of Hudson’s Bay Saturday night and Sunday.  That one reinforces the chilly airmass.  So both Saturday and Sunday we’ll see gusty east wind in the Metro Area.  Nothing too crazy there, maybe gusts 50-55 mph.  Temp forecasts for Saturday and Sunday are tough.  If it was Halloween I’d say highs around 48-50 degrees, especially Sunday.  So I went with 55-60, coolest on Sunday with the 2nd push of colder air.

The airmass coming in is going to be very dry…dewpoints at least down into the 20s.  Couple that with clear skies and the calm wind locations should have a hard freeze Saturday and Sunday nights.  I think the only spots that will avoid this will be east Portland out through the west end of the Gorge.  Will the wind drop off Saturday or Sunday night at PDX?  Seems unlikely with 6-7 mb of gradient through the Gorge and a cool airmass, but it could happen.  Cooler east wind hangs on at the Airport overnight much better than the warmer wind we get in early Fall.

Okay, out of time for now.  Still looks wet beginning Tuesday.

Chief Meteorologist Mark Nelsen