This morning's showers are expected to continue as a southwesterly flow prevails ahead of an incoming cold front.
It will become more rainy and snowy in the mountains later today, with heavy snow possible in the Cascades this evening and into Thursday early. As a result of the cold front passing through Thursday afternoon, precipitation will be limited to showers.
As we go into the holiday weekend, much colder air will flow into the area, which will remain for the rest of the week.
Additional meteorological disturbances will keep the prospect of precipitation throughout the cold weather alive, perhaps bringing heavy snow to the lowest altitudes of the mountain ranges as well.
From now through Friday, because of the southwesterly flow continuing ahead of a coming Gulf of Alaska cold front, mild weather and isolated showers are expected to prevail over most districts.
A layer of cooler air has remained stuck in the Hood River Valley, resulting in some sporadic freezing rain as the storms pass across the area. Temperatures remain marginal for any consequences near the river/I-84 level, but some ice is anticipated to develop on untreated roadways when temperatures rise above 500-1000 feet to closer to 30 degrees Fahrenheit.
As a result, the Winter Weather Advisory in effect for the upper Hood River Valley will remain in effect for a few more hours, after which temperatures should gradually reduce around daybreak.
Late tonight and early Thursday morning, the aforementioned cold front will pass southeast through the forecast area, bringing rain to the area. After this front passes through, the air mass behind it will be much colder, reducing snow levels to roughly 2000 feet on Thursday.
With this frontal system, the chance of reaching winter storm criteria in the Cascades looks to be minor, but it is near enough that we will keep the warning in place. Currently, 10 to 18 inches look reasonable bet above 4000-5000 ft elevation.
With a respite in between, expect two waves of precipitation: one later tonight into this evening, and another along with the cold front Thursday morning. It will be necessary to monitor QPF throughout the Oregon Coast since rivers are already overflowing due to recent rainfall.
Precipitation after the next Gulf of Alaska cold front will continue through Friday, with some enhancement and a spell of stratiform rain and mountain snow possible later Thursday night into Friday when the next cold front goes through.
The fact that snow levels are dropping into the foothills, combined with a plentiful supply of moisture, means that this front might deliver warning accumulations of 6 or more inches to the Coast Range and Cascade foothills.
Another storm will bring more showers on Christmas Eve, but the southerly flow should maintain snow levels above the valley floors, at least for the time being.