Mountain Weather Forecast

Weather Synopsis

A complex system will bring impactful weather and significant snowfall focused on the southern half of our forecast region through Thursday afternoon. Snow started around Mt Hood around noon as a warm front lifts slowly northward. The associated low pressure sits of the Oregon coastline and tracks slowly toward the mouth of the Columbia River. The warm front will bring increasing moderate to heavy snow Wednesday night to areas from Mt Hood to Mt Rainier, with higher snowfall rates also possible with E slope enhancement for the Wenatchee Mountains and Icicle Creek areas. The combined upper-level support of ESE winds aloft and increased low-level pressure gradients will drive moderate winds through the mountain gaps and along exposed ridgelines near and west of the Cascade Crest, with peak winds Wednesday night. The front lingers near the coastline or shifts slightly onshore on Thursday, bringing the highest snowfall rates to the SE Olympics, but continued decreasing moderate to locally heavy snowfall for the southern volcanoes and Wenatchee Mountains. Storm totals should be in the 20-30" range for Mt St Helens, 15-20" range for Mt Hood and Paradise, and 5-15" range for most other areas south of I-90. Snowfall amounts decrease dramatically from Snoqualmie Pass northward, where we expect 1-4" accumulations, with only a dusting for Mt Baker. Temperatures will be favorable for high snow-water ratios and snow levels hovering near or just above sea level.

Snow showers taper or end over much of Washington State Friday evening as the remnants of the low move onshore. A stationary front lingers over North Oregon Thursday night and weakens Friday as ridging brings a mostly dry day on Friday. Expect a cold start to the day with freezing levels rising rapidly up to the 3000 ft range for the west slopes of the Cascades. E flow increases as an offshore frontal system approaches.