textproduct: Pendleton

DISCUSSION

A progressive pattern featuring a 500 mb trough over the Intermountain West placing northwest flow aloft across the Pac NW/Eastern WA and OR and resulting in winter wx advisories for some of the mountains zones. Previous days snow stick at Mt Bachelor showed 5 inches in 24 hours ending yesterday afternoon, with an additional inch last evening. HREF trends are following the ramp down of snow accumulations over the Oregon Cascades Eastern Slopes and a ramp up of snow across the Northern Blue Mountains of Oregon This Morning lingering though the end of the day. With that, the advisory for OR509 will be allowed to expire at 12z while the advisory for areas higher than 4000 ft remains for the northern Blue Mountains of Oregon and Washington.

Added momentum transfer should kick in by mid morning with mixing, as steady winds overnight have been already breezy/gusty (as high as around 30-33kts) at PDT. NBMs mean surface gust fields across the Foothills of the Blues are in the 35 to 40 knots range This Afternoon, which can qualify for a wind advisory extending from non mountain zones north central Oregon and the Simcoe Highlands, to Umatilla County and the Oregon/Washington Highway.

An uptick in the snow across the mountain zones may develop again Thursday night. Even into the Friday timeframe, the IVT shows much stronger values 300-400 kg/ms. The lack of really high pops during this period may be due to the more parallel juxtaposition to the orographic forcing/Cascades. In the more medium range, the period beginning around Monday onward might see impactful snows across the WA Cascade Crest. Impact likelihood for minor impacts/winter driving conditions is 60-70% for the Pass areas, and about 20-30% for roughly Monday night through Tuesday Night. This also shows up in the GEFS/ENS mean ensemble plumes at Snoqualmie Pass that could linger through about mid week.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

VFR cloud bases and breezy to windy conditions will be the prevailing weather conditions for the terminals Today. Lowest ceilings should still be about 4,000 ft or higher in the foothills regions like ALW and PDT.

Preliminary Point Temps/PoPs

PDT 51 34 53 42 / 20 20 30 20 ALW 52 37 53 43 / 40 20 40 40 PSC 59 36 60 44 / 0 10 10 20 YKM 54 35 58 42 / 0 10 10 20 HRI 57 37 58 43 / 10 10 20 20 ELN 48 34 52 41 / 10 20 20 20 RDM 46 27 49 33 / 10 10 10 10 LGD 45 31 48 38 / 70 30 40 40 GCD 42 29 45 35 / 50 20 40 20 DLS 53 41 55 45 / 20 30 40 30

PDT WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until 10 PM PST this evening for WAZ030. Wind Advisory from 7 AM this morning to 7 PM PST this evening for WAZ521. OR...Winter Weather Advisory until 10 PM PST this evening for ORZ502. Wind Advisory from 7 AM this morning to 7 PM PST this evening for ORZ507-508-510. Winter Weather Advisory until 4 AM PST early this morning for ORZ509.