textproduct: Pendleton

KEY MESSAGES

- Southwest flow through Monday will bring shower and isolated thunderstorm chances mainly to far eastern Oregon.

- Breezy westerly winds and low relative humidity Tuesday afternoon and evening, especially across the Columbia Basin of Oregon.

- Another chance of showers and thunderstorms toward the weekend.

DISCUSSION

Southwest flow will continue through Monday. Several short waves will move through the flow. These short waves coupled with residual moisture could trigger showers and isolated afternoon thunderstorms, mainly for Wallowa County, but other mountain areas can't be ruled out.

By Tuesday, the Pacific Northwest gets into more of a split flow pattern and as a result, west winds will increase across the area. Winds will become gusty beginning Monday night and into Tuesday, with wind gusts 20 to 30 mph, with some locations possibly as high as 35 mph, in the usually breezier areas such as the Kittitas Valley, Simcoe Highlands, Blue Mountain Foothills, Columbia Basin and Gorge. NBM probabilities of wind gusts >=25 mph are >60 percent, while NBM probabilities of wind gusts >= 39 mph are generally 50 percent or less.

RH values do decrease a bit between Monday and Tuesday and with the gusty winds, fire weather conditions will be elevated, and could become critical. A Fire Weather Watch was issued for the Lower Columbia Basin of Oregon (OR691), in effect Tuesday afternoon and evening. Additional headlines may be needed, but confidence was too low to issue today.

Beyond Tuesday, the midweek period looks rather quiet, in dry west to southwest flow.

However, by the weekend an area of low pressure will move northward off the coast. This low is then expected to move onshore in Oregon or Washington at some point on Saturday. There is still some disagreement as to where the low comes ashore and how strong it will be and the natural uncertainty in a forecast 5 days out, but shower and thunderstorm chances do look to increase, especially for the mountains as we head into the weekend.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

VFR conditions are forecast at all sites through the period, except for temporary MVFR due to a layer of smoke presenting a ceiling at BDN late this evening. Otherwise, there is low confidence (20%) in any smoke impacts redeveloping at sites, though if impacts do occur expect reduction in VSBY in the overnight and early morning hours. Winds will be predominantly light at 10 kts or less, except at DLS where breezy westerly winds are forecast during the late afternoon and evening hours on Monday. Skies will consist of SCT-BKN mid/high cloud for the majority of the period.

FIRE WEATHER

Isolated showers and thunderstorms (<20% Monday) are possible mainly across Wallowa County in southwest flow.

As the flow becomes more westerly Monday night into Tuesday, winds will increase and become gusty, with gusts as high as 20 to 30 mph and possibly as high as 35 mph across the Kittitas Valley, Simcoe Highlands, Blue Mountain Foothills and the Columbia Basin and Gorge. These winds and low relative humidities will yield elevated fire weather conditions Tuesday and could bring critical conditions once again.

Beyond that, there is the potential for more thunderstorms going into next weekend.

Preliminary Point Temps/PoPs

PDT 57 89 58 90 / 0 0 0 0 ALW 63 91 64 90 / 0 0 0 0 PSC 59 94 60 94 / 0 0 0 0 YKM 60 94 61 93 / 0 0 0 0 HRI 61 92 63 93 / 0 0 0 0 ELN 58 90 60 86 / 0 0 0 0 RDM 51 88 49 90 / 0 0 0 0 LGD 57 92 57 91 / 10 20 20 0 GCD 56 92 56 92 / 0 10 10 0 DLS 60 93 62 89 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Air Quality Alert until noon PDT Monday for WAZ026-522-523. OR...Air Quality Alert until noon PDT Monday for ORZ041-503-505-506- 508>511. Fire Weather Watch from Tuesday afternoon through Tuesday evening for ORZ691.