Thursday, September 26, 2013

Stormy Days Ahead for Pacific Northwest

The month of September has been wetter than normal so far in most of Washington, Oregon, and Idaho after a dry summer. Drought has been absent from all but a small portion of Washington but still encompasses most of Oregon and Idaho as well as the remainder of the western states except for the eastern two-thirds of Montana.

It looks like it will get a lot wetter the next 3 to 5 days. A series of strong storm systems will slam into the Pacific Northwest producing copious amounts of rain. The first and strongest of these storms will arrive this weekend, and up to six inches of rain could fall from the Cascades to the coast.

Northern Pacific 500 millibar forecast map for Sunday, September 29 at 5:00 p.m. PDT

Quantitative precipitation forecast for the three days ending 5:00 p.m. PDT Sunday, September 29

Higher amounts could accumulate over west facing slopes of the Cascades where the moisture-laden onshore flow will be forced upward by the terrain. The first half of next week will be cloudy and showery as the large upper level trough remains over the region and smaller disturbances rotate through it.  A second system may bring more significant rain about midweek, though this system should be weaker.

The 5-day quantitative precipitation forecast for the period ending 5:00 p.m. MDT Tuesday, October 1.

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