textproduct: Pendleton

KEY MESSAGES

- Dry and warm weather through Friday.

- Low pressure will approach the region on Friday and will move inland late Friday night or early Saturday, bring shower and thunderstorm chances, mainly to the mountains and gusty winds.

- Fire weather conditions look to become elevated, if not critical as we approach the weekend.

DISCUSSION

Southwesterly flow will remain over the Pacific Northwest as the region remains between a large area of high pressure over the four corners and low pressure over the Pacific Ocean.

Heights will rise over the area through Friday and temperatures are expected to rise into the mid to upper 90s both Thursday and Friday. HeatRisk values will be widespread moderate on Thursday with some local Major Risk. The usual caveats apply to temperatures. The presence of wildfire smoke will affect afternoon high as it has for much of the summer, and clouds should be increasing on Friday, as the offshore low approaches, which could also temper the high temperatures.

The low in the Pacific will move northeastward towards the Washington and Oregon coasts through Friday. It will then move onshore with late Friday night ore early Saturday as an open trough, before continuing northeastward into British Columbia.

Latest guidance has trended slower with the motion of the low, an most of Friday now appears dry. There could be some showers/thunderstorms over far western sections of the area during the afternoon, but most of the precipitation chances look to occur during the evening/overnight hours on Friday and then Saturday looks to be the better day for shower or thunderstorm potential, mainly in the mountains. Right now, chances remain about 15 to 20 percent for thunderstorms, while shower chances are higher (30-40 percent), especially over the Oregon Cascades Friday evening/night and Washington Cascades on Friday night/Saturday.

Additionally, as the trough moves and associated cold front moves across, winds will increase on Saturday and become gust, with wind gusts 25 to 35 mph possibly as high as 45 mph in the normally breezier locations...the Kittitas Valley, Simcoe Highlands, Columbia Basin, Gorge and Foothills of the Blue Mountains. In these areas NBM probabilities of wind gusts >=39 mph range from 50 to >90 percent. Wind gust probabilities >=47 mph range from 10 to over 60 percent locally.

The strong winds will meet with marginal RH values that will be marginal for Red Flag Warning criteria. Will continue to monitor this, and conditions will be elevated, but confidence is not high enough that they will reach critical levels.

Beyond Saturday, we get into a drier west to eventually southwest flow.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

VFR conditions perisit through the forecast period. Winds will be generally light under 12 kts. There is low confidence (10-15%) in smoke making it to the surface and reducing VIS to 5SM or MVFR conditions.

FIRE WEATHER

Dry conditions with low relative humidity is expected through Friday. Then, an area of low pressure will approach the region and move onshore late Friday night or early Saturday. This low could touch off some showers and thunderstorms, mainly over western areas in the afternoon on Friday, but the better (yet still low (<20 percent) chances of thunderstorms look to be Friday night and Saturday over the mountains.

Additionally, as the low and associated cold front moves northeastward, winds will increase across the region, gusty west winds will develop on Saturday. Winds could gust 25 to 35 mph, with gusts possibly as high as 40 to 45 mph especially across the Kittitas Valley, Simcoe Highlands, Columbia Basin, Gorge and Foothills of the Blue Mountains. RH values will rise with the frontal passage. Fire weather conditions will be elevated and could become critical on Saturday, but RH values currently are marginal.

Preliminary Point Temps/PoPs

PDT 56 95 62 95 / 0 0 0 0 ALW 64 97 67 99 / 0 0 0 0 PSC 56 97 61 99 / 0 0 0 0 YKM 61 98 65 98 / 0 0 0 0 HRI 59 97 64 97 / 0 0 0 0 ELN 60 94 64 95 / 0 0 0 0 RDM 50 96 56 94 / 0 0 0 0 LGD 57 98 61 100 / 0 0 0 0 GCD 57 98 61 100 / 0 0 0 0 DLS 62 99 67 96 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...Air Quality Alert until 11 AM PDT Thursday for ORZ050-502-505- 506-509>511.