Winter knocks again: Rain and mountain snow this weekend

Weather

PORTLAND, Ore. (KOIN) — Rain starts your Friday morning across SW Washington and NW Oregon, but may not reach the remaining valley to the south until midday. This will be the light variety as a cold front saunters across the Pacific Northwest. We’re working with an elongated trough which is essentially slowing and weakening this front. A cousin to this front will split off over the weekend and potentially direct rain and mountain snow to California.

In this water vapor imagery notice what appears to be popcorn NW of Vancouver Island. That is a nice red flag for instability.

Aside from the rain, the one thing that will get your attention is the relatively cold air. Daytime highs and morning lows will barely differ today: mid to upper 40’s expected. We’ve been skating by this week with temperatures above normal since Tuesday. What is normal, anyway? It’s 54° for Portland in early March. For our Puget Sound neighbors to the north it will be cold enough to snow at 500′ to 1,000′ today, yet still too warm to collect on roadways.

Forecast rain totals for the day are not likely to exceed 0.40″ in the Willamette Valley. Add Saturday and the two-day total is closer to 0.60″. Something is better than nothing. March rain so far has been under performing. PDX rain totals are -0.67″ below normal month to date — a very different situation compared to how we started this year. January was an overly abundant rain month, but we fell short in the month of February. 

Forecast snow totals for the Cascades will be minimal to start — perhaps only 1 inch over mountain passes today. Saturday is a different animal. Watch for snow falling as low as Sunset Summit Saturday morning. Also, like last Saturday, colder air aloft coupled with other atmospheric dynamics spells i-n-s-t-a-b-i-l-i-t-y. This may lead to thunderstorms. Watch for downpours and hail. If you you’re out playing sports Saturday – remember when thunder roars, go indoors.

P.S. Spring your clocks forward Saturday night before you go to bed. It’s that time of year again.

These are forecast temperature contours at 850 mb or approx. 5,000 feet. Coldest time period will be Saturday behind the cold front.

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