** Updated 2/20, 3:15PM: NOAA officially issues Flood Watch for Snoqualmie Valley. “SOME UNCERTAINTY STILL EXISTS. HOWEVER RECENT WEATHER MODELS HAVE FORECAST THE HEAVIEST RAINFALL IN EASTERN KING AND SNOHOMISH COUNTIES. IN THIS AREA OF THE CASCADE MOUNTAINS 4-7 INCHES IS FORECAST…WITH SOME HIGHER BULLSEYES. THE RIVERS AT GREATEST RISK OF MAJOR FLOODING ARE THE ONES FLOWING OUT OF THIS AREA…THE STILLAGUAMISH… THE SKYKOMISH…THE TOLT…THE SNOHOMISH…AND THE SNOQUALMIE.” **
The National Weather Service says a rain storm is headed toward Western Washington, one bringing lots of soaking, tropical moisture, high snow levels and strong westerly air flow. The warm, westerlies slam up against the west slopes of the Cascades which increases rainfall amounts there. The Cascades saw massive amounts of snow over the weekend. The Summit at Snoqualmie alone received 31 inches of new snow. Now warmer weather is on the way, which melts all that new snow and forces run-off into mountain-fed rivers. It’s a classic weather scenario for Snoqualmie Valley flooding; whether it’s minor or major flooding.
Weather forecasters say tomorrow’s weather system is similar to the one that produced major Snoqualmie Valley flooding in November 1990. Don’t panic, though, those same forecasters also go on to say that the 1990 storm “was much stronger and lasted longer than this one will.” Approximately 3-6 inches of rain is predicted for the central Cascades starting 4AM Tuesday – 4PM Wednesday. Snow levels will hover around 6,000 ft. the entire time. Flood-prone rivers flowing off the west slopes of the Cascade have the greatest flooding threat with this incoming weather system – that includes the Snoqualmie and Tolt Rivers.
As with any incoming storm in our area, the path is critical. If it veers a little more south or north, the rain total amounts can decrease. You can check the latest weather forecasts at NOAA’s Snoqualmie Valley local page. If you want a forecast pinpointed exactly for your neighborhood, simply click on the map and the forecast will change. If needed, you can monitor Snoqualmie River flooding at King County’s Flooding Services page. Any flooding that happens will most likely occur Tuesday night or Wednesday, February 22nd.