Here is the story at 6 AM. The commute for Seattle and to its west should be uneventful. The winds aloft are still westerly aloft that we are in the rainshadow of the Olympics and that should not change much before 8 AM. As normal for rainshadow, precipitation picks up in the eastern suburbs east of Lake Sammamish. Snow showers are moving into the region, but as seen in the radar most of the action is north of Everett and south of Bellingham. So Whidbey Island, the San Juans, and the northern Olympics are seeing snow showers now, some occasionally heavy.
In fact, you will notice the heaviest precipitation is over the eastern Strait and westward and that is probably due to the convergence of modest NE flow coming out of the Fraser and southerly wind coming up the Sound and westerly wind moving eastward in the Strait (see map below). Such low level convergence forces upward motion. WATCH THAT BOUNDARY--that is where the big action will be today. Go south of McChord and there are snow showers moving through the Chehalis Gap. Moderate to heavy snow on the western slopes of the Cascades and foothills.
So bottom line for Seattle commuters...you will have no problem getting into work. Temperatures are above freezing and road surfaces are wet. Looking at the satellite pictures (see below) I am not impressed with what is coming in from offshore. Not much cooling of the cloud tops (such cooling means deepening of the clouds and intensification). The models indicate that during the day the flow approaching the region will weaken and turn more southerly....that will open Seattle to snow showers, and as the low moves south, northerly flow will push southward. But not yet.
Last night the NWS was going for a hard freeze of this stuff later today during the commute home. Looking at the situation now I believe that is highly unlikely. Temperatures will remain at or slightly above freezing during the day. Major urban roads should be ok, particularly since many DOT's applied deicers. The only failure mode would be if the snow rate gets SO large that we get a slippery slush layer after the deicers get diluted.
Reminder...my talk at Ivar's Mukilteo has been delayed to March 9 due to snow forecast. It will not be good if it doesn't snow!
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