Low Snow Levels Friday Night - Saturday Morning

By Rod Hill on 2020-03-13

Friday - Saturday forecast discussion for possible snow accumulation:

Light precipitation becomes possible Friday morning,
but heavier rainfall will hold off until closer to the noon hour as the developing
low pressure center approaches the coast. Look for rainy weather much of this
afternoon and periods of heavier rainfall Friday night. Daytime temps on this Friday
will hold in the 40s and likely go no higher from the noon hour.  Morning variable 
winds will back to the southeast - east to 15 mph. 

As rain picks up overnight, so will the east winds, gusting to 25 mph by morning, to 
30 near the gorge.  The air mass gets sharply colder Friday night, dropping snow 
levels for accumulating snow to near 1,000 feet.  Lowest elevations in the valley, 
including Portland will see overnight temps near freezing to holding in the mid 30s. 
Due to available moisture amounts of .25-.50” Friday night through Saturday morning, 
significant snow accumulation will be at least possible and this forecast should be 
watched closely.  Forecast guidance believes Portland will hold in the mid 30s with
rain and a snow mix in the air, but a few degree drop with east winds blowing and the air
mass could quickly drop accumulation snowfall. 

Especially areas near 1,000 feet should watch for snow on the ground. 

The threat of snow and winter precipitation quickly ends by noon Saturday as daytime
temps rise to 40 degrees and the moisture field dries up as the surface low drops to 
our south.  Saturday daytime highs may warm into the mid 40s with gusty east winds
15-35 mph.  

Mostly dry weather Saturday evening and overnight and Sunday with partly cloudy skies. 

A hard freeze in wind protected areas (blocked from the east wind)  is still likely Sunday, 
Monday and maybe Tuesday mornings.  Coldest temps could drop into the mid 20s. 

Rod Hill