textproduct: Pendleton

KEY MESSAGES

- Low (<20%) shoer and thunderstorm chances this afternoon and evening across far eastern Oregon.

- Gusty west winds and low relative humidity will combine to create critical fire weather conditions Tuesday afternoon, mainly across the Columbia Basin of Oregon.

- Another chance of showers and thunderstorms and gusty winds toward the of the week, associated with an upper low.

DISCUSSION

Southwesterly flow over the region today will give way to a more split flow regime on Tuesday. There is still a low <20 percent) possibility of showers and thunderstorms, mainly across Wallowa County and the Blue Mountains as some short waves move through, but chances are lower than the last few days.

The split flow that develops overnight into Tuesday will bring gusty westerly winds. These winds could gust as high as 30 mph across the Kittitas valley, Simcoe Highlands Columbia Basin, Gorge and Foothills of the Blue Mountains. Across all of these areas, except the Kittitas Valley, where RH values are expected to be a bit higher, Red Flag Warnings have been issued for Tuesday.

After Tuesday, the region is expected to remain in a dry west to southwest flow through midweek as low pressure moves from southwest to northeast off the Pacific Coast. As we approach the weekend, the low is expected to weaken into an open trough and move onshore in Washington/Oregon likely sometime on Saturday.

There are still some differences in the models that have to be resolved, but overall there is decent agreement. Winds will likely increase beginning Friday and even more into Saturday and continuing into Saturday night before decreasing. Winds could gust in the 25 to 35 mph range, and possibly to 40 mph, especially across the normally breezier areas of the Kittitas Valley, Simcoe Highlands, Columbia Basin, Gorge and Foothills of the Blue Mountains. At this point, NBM probabilities of wind gusts >=25 mph are >80 percent in these locations while wind gusts >=39 mph >40 percent.

Additionally, the exact position and timing of the trough will determine precipitation threat, but there is at least some threat of showers and thunderstorms later Friday into Friday night and, potentially a better threat on Saturday.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

VFR conditions will persist through the forecast period. Confidence remains low (15-25%) in vsby reducing to MVFR or lower at sites due to smoke impacts except at RDM which is MVFR and will stay as such through much of the period. Winds will be below 12 kts across all sites except DLS which is at 10g15 and all. Breezy winds will increase tomorrow afternoon at sites DLS/PDT/RDM/ALW.

FIRE WEATHER

There remains a low (<20 percent chance of showers and thunderstorms across far eastern Oregon this afternoon and evening.

The next threat is for gusty west winds developing on Tuesday, mainly across the Oregon Columbia Basin and surrounding areas, as humidity values remain low (around 15 percent). Fire weather conditions will become critical in these areas and Red Flag Warnings have been issued.

After Tuesday, the next time period of concern looks to be closer to the weekend as an area of low pressure approaches the Oregon and Washington coasts. Winds will increase and become gusty especially on Saturday and there will be at least some shower and thunderstorm potential, over the mountains. All of the finer details will come into better focus over the next few days.

Preliminary Point Temps/PoPs

PDT 58 91 54 90 / 0 0 0 0 ALW 65 92 62 91 / 0 0 0 0 PSC 60 95 57 93 / 0 0 0 0 YKM 60 95 60 92 / 0 0 0 0 HRI 62 93 60 92 / 0 0 0 0 ELN 59 87 58 88 / 0 0 0 0 RDM 49 91 48 92 / 0 0 0 0 LGD 57 92 54 93 / 20 0 0 0 GCD 56 93 55 95 / 10 0 0 0 DLS 62 90 60 91 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...Air Quality Alert until 1 PM PDT Wednesday for ORZ041-505-506- 509>511. Red Flag Warning from noon to 10 PM PDT Tuesday for ORZ691-701- 703.