First, here are the snow reports from the Seattle NWS office:
PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE SEATTLE WA
610 PM PDT SUN NOV 21 2010 ..
SNOWFALL TOTALS THROUGH SUNDAY AFTERNOON...
KING COUNTY SNOWFALL(IN) TYPE
ENUMCLAW 6(MILES)NNE 3.5 SPOTTER
PIERCE COUNTY SNOWFALL TYPE
EATONVILLE 3.0 SPOTTER
PUYALLUP 5 WSW 1.1 SPOTTER
PUYALLUP 4 SSE 1.0 SPOTTER
LEWIS COUNTY SNOWFALL TYPE
ETHEL 4 SW 1.5 SPOTTER
THURSTON COUNTY SNOWFALL TYPE
GRAND MOUND 5 NNW 1.8 SPOTTER
CLALLAM COUNTY SNOWFALL TYPE
FORKS 2.0 CO-OP PORT ANGELES 4W 1.9 SPOTTER
Most of region had a few flurries or some drizzle, with the heaviest snow concentrated near or just west of the foothills southwest of Seattle. Puyallup and Federal Way had some sticking light snow. Also some snow in the Shelton area and the northern Coast.
The weather service is going for a 70% chance of snow tomorrow...with 1-3 inches.
Seattle DOT is applying anti-icing substances on the roads tonight (a good precaution) and Metro is putting its vehicles on snow routes tomorrow morning (commendable perhaps but probably unnecessary).
The latest model runs are in and here it is (24h total ending 4 PM tomorrow).
Bottom line...NO ACCUMULATING SNOW in Seattle, but white stuff over SW Washington and Oregon. We could get a few flurries like today.
and here is the latest probcast probability of precipitation based on ensembles and statistics. Same story. Very low probability of precipitation in Seattle. Again, no accumulating snow.
The weather channel...which computes an independent forecast... is going for scattered snow showers and snow of less than an inch in Seattle.
Again, my conclusion....no accumulating snow in or north of Seattle. But if you are driving south, particularly south of Olympia, the chances go way up. Also snow in the mountains and foothills and along the coast. SDOT and Metro can probably rest easy.
But it will be cold..tonight the temps will dip into the 20s in many locations and the winds will pick up. Really strong NE winds over NW WA and northerlies pushing down the Sound. Temperatures dropping into the low 20s and teens on the west side of the State on Tuesday AM...it will be brutal. And east of the Cascades them combination of strong wind and temperatures in the single digits will produce extreme, dangerous conditions on Tuesday.
Finally, for users of probcast...it has a problem with minimum temperatures that will be fixed soon...don't take crazy low temps seriously (unless you work for some TV station weather hype dept!).