Here is the 24 hr precipitation ending 8 AM Friday for sites with more than .5 inch. Some locations on the western slopes of the Cascades and Olympics have already gotten two inches.
The precipitation over the same period from Seattle RainWatch (based on calibrated radar data) shows a profound rainshadow NE of the Olympics, but 1.5-2 inches along the western Cascade slopes.
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It is now clear that we are going to have one of the wettest periods in a while starting today, with less rain in the lowlands and much more in the mountains.
An infrared satellite photo late Thursday, shows the moisture arching into our region
Let me show you a sequence of 24h precipitation totals from the UW WRF modeling system. For the period through 5 PM Friday there is 1-3 inches in the mountains. Note that Puget Sound region is drier--the is due rainshadowing to the east of the Olympics Mountains, something expected from the westerly flow regime we will be in.
Far more serious the next 24 h, with some locations in the southern Cascades seeing 5-10 inches
Adding up the entire period is impressive and scary (see below), with 5-10 inches over much of the WA Cascades and mountains of southwest WA, with some peaks getting even more.
This will be enough water to push some westside rivers, and particularly those near and south of Mt. Rainier, to flood stage. The NW River Forecast Center is predicted a number of local rivers to hit flood stage, with some attaining a moderate flood.
The hydrograph plot for the Snoqualmie River near Carnation shows the story with an extraordinary rapid rise predicted.
The snow forecast for the period is on track, with the amounts being enhanced from the previous forecast cycle (see below).
Need more weather fun?...no problem. Strong winds will be found along the coast, NW Washington, and on exposed mountain peaks.
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