textproduct: Pendleton

KEY MESSAGES

- Breezy to locally gusty winds through the Cascade Gaps and across the Columbia Basin today

- Near to below normal temperatures through the weekend

- Dry conditions with light winds into the middle of next week

UPDATE

A Wind Advisory has been issued for the Columbia River Gorge of WA and OR, the western lowers Columbia Basin of OR, the Southern Foothills of the Blues and the Simcoe Highlands of Klickitat County. NBM Raw ensembles shows 60-80% probabilities of sustained winds of 20-30 mph with gusts between 40-50 mph beginning after 11 AM and persisting through 11 PM. The Winds Advisory for Kittitas Valley remain ins effect through 11 AM for sustained winds of 25-35 mph with gusts up to 50 mph with high probabilities of 80-90%. 90

DISCUSSION

Today: Convective activity has come to an end across the PacNW tonight, with lingering light showers still hanging on across the central WA and OR Cascade crest with clear/dry conditions across the remainder of the forecast area. Otherwise, quiet conditions have developed across much of the forecast area, except for breezy winds that have developed through the Cascade gaps.

Today, the upper low/trough over the Great Basin will swing northeast into the central/northern Rockies, pulling the trough axis and an area of diffluence aloft over the forecast area. This will revitalize isolated to scattered showers across the Cascade east slopes, central OR, and the Yakima/Kittitas valleys this morning, with shower activity spreading across the eastern mountains by this afternoon. Isolated thunderstorms will also be possible across the eastern mountains as surface instability (250-500 J/kg) and low level lapse rates (8-9.5 C/km) increase in the afternoon. Otherwise, a surface pressure gradient setting up over the Cascade crest will produce persistent breezy winds through the Cascade Gaps and across the Columbia Basin, with the strongest winds (25-35mph with gusts 45-55mph) developing through the Kittitas valley this afternoon and evening.

Saturday through Tuesday: Over the weekend, the upper low will slowly swing northward across the northern Rockies, placing the region under a cool westerly flow that will keep afternoon temperatures in the mid 60s to mid 70s. Conditions will remain dry across the forecast area through this period while winds will become light as the Cascade crest pressure gradient breaks down. There is, however, a low chance (<10%) for isolated light showers to develop across the mountainous terrain across Wallowa County as moisture attempts to wrap around the upper low to the east.

By Monday, a weak upper ridge will build over the PacNW as the low lifts into Canada, continuing the dry and weak wind trend across the forecast area. The ridge overhead will also promote a weak warming trend that will bring lower elevation temperatures back into the lower to mid 80s by Tuesday (confidence 60-75%).

Wednesday and Thursday: Ensemble cluster guidance is in good agreement that a shortwave trough ejecting from an upper low in the northeast Pacific will slide across the PacNW Wednesday, producing light rain showers across the mountainous terrain and breezy conditions in the lower elevations (confidence 60-65%). Weak, broad ridging will then build back over the PacNW with drier conditions and locally breezy conditions for Thursday (confidence 50-60%). That said, there are some ensemble cluster members (~20%) that favor troughing over the PacNW, resulting in continued chances of showers across the Cascades, Blues, and Wallowas for Thursday. Lawhorn/82

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

VFR conditions will generally prevail through the period. The only exception is at RDM, where there has been some MVFR CIGS this morning. These CIGS may linger for another hour or two before returning to VFR.

Otherwise, expect expect gusty winds to around 30 kts this afternoon at DLS, YKM and PDT and 20 to 25 kts at most other sites. Winds should decrease to 10 kts or less overnight. DLS and PDT will gust to around 25 kts on Saturday afternoon as well.

Preliminary Point Temps/PoPs

PDT 68 41 67 42 / 10 10 0 0 ALW 71 47 68 47 / 0 10 10 0 PSC 74 45 73 43 / 10 10 0 0 YKM 72 43 72 42 / 60 0 0 0 HRI 69 43 70 43 / 10 0 0 0 ELN 65 39 65 40 / 50 0 0 0 RDM 59 31 62 30 / 80 0 0 0 LGD 72 41 64 37 / 40 10 10 0 GCD 67 36 65 34 / 50 30 0 0 DLS 67 45 69 45 / 30 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 11 PM PDT this evening for WAZ024-026-521. OR...Wind Advisory until 11 PM PDT this evening for ORZ041-044-508.