textproduct: Pendleton

KEY MESSAGES

- A Very low chance (<20 percent) of showers and thunderstorms from the Blue mountains eastward this afternoon and evening.

- Above normal temperatures with widespread moderate heat risk today and Wednesday.

- A tightening pressure gradient in response to low pressure moving into British Columbia will bring increased winds Wednesday and even breezier conditions on Thursday. Fire weather conditions will approach critical on Wednesday over portions of the Columbia Basin an Gorge. Despite stronger winds Thursday, RH values will be higher as well.

DISCUSSION

Strong high pressure over the southwest will bring warm and generally dry weather to the region through Wednesday. The only caveat, is a very low (<20 percent) chance of afternoon and evening showers and thunderstorms over the Blue Mountains and Wallowa County today as some weak short wave energy movers through.

Otherwise, it will be very warm, with afternoon high temperatures in the low to mid 90s. These temperatures are about 5 to 10 degrees above normal, depending on location, with today's temperatures a tad warmer than on Wednesday. HeatRisk is expected to be widespread Moderate both days.

By Wednesday, an area of low pressure will be moving northeast off the coast toward British Columbia and will move inland in British Columbia Wednesday night or early Thursday. As this low moves closer, the pressure gradient will increase between it and the strong high pressure over the southwest. The increased pressure gradient will cause an increase in winds beginning Wednesday and a further increase on Thursday.

Additionally, while the main upper trough stays to the north, a cold front will move through and this front will bring cooler temperatures on Thursday and we will get into a more split flow pattern, then a more westerly flow through the weekend.

Winds will gust in the 25 to 30 mph range, possibly as high as 35 mph in a few spots Wednesday afternoon, mainly across the Cascade Gaps, Simcoe Highlands and Columbia Gorge and Oregon Columbia Basin and Foothills of the Southern Blue Mountains. NBM probabilities of wind gusts >=25 mph are >80 percent in these areas. However, wind gusts >=39 mph are generally less than 30 percent, with a few local areas >= 50 percent.

The combination of the wind gusts and low RH values will bring elevated to critical fire weather conditions and portions of the Columbia Basin and Gorge will have to be monitored for fire weather headlines.

On Thursday, winds are possibly a tad stronger and more widespread than on Wednesday. A very large portion of our area has probabilities of wind gusts >=25 mph that are >70 percent. It is mainly the Simcoe highlands, portions of the Basin, Gorge and Kittitas Valley that have >50 percent probabilities for wind gusts >39 mph. However, with temperatures 8 to 10 degrees cooler than on Wednesday, RH values will be about 5 to 10% higher on average. This will keep fire weather conditions elevate but should preclude any critical conditions.

For those sky watchers out there, this Thursday night, August 27th, there will be a partial (but 93%) lunar eclipse. With sunset being around 740 PM or so, depending on your location, the moon will already be in eclipse when the sun goes down. Peak eclipse will be around 912 PM PDT and the eclipse will end around 1051 PM PDT. At this point, the sky looks to be relatively clear, the only concern will be if there is any smoke or haze from nearby wildfires in your vicinity.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

VFR conditions are mainly expected at all TAF sites through the period. However some local MVFR can not be ruled out, especially at PDT and ALW through the morning hours.

Gusty winds will develop at BDN, RDM and DLS through the afternoon and evening hours before decreasing. Winds could gust in the 20 to 25 kt range. All other sites should be 10 kts or less.

Preliminary Point Temps/PoPs

PDT 94 59 92 58 / 0 0 0 0 ALW 95 66 93 65 / 0 0 0 0 PSC 95 61 96 61 / 0 0 0 0 YKM 95 62 95 59 / 0 0 0 0 HRI 95 63 94 61 / 0 0 0 0 ELN 92 61 91 56 / 0 0 0 0 RDM 95 50 91 48 / 0 0 0 0 LGD 97 58 97 56 / 20 20 10 0 GCD 96 58 96 56 / 10 10 0 0 DLS 95 64 89 62 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Air Quality Alert until noon PDT Wednesday for WAZ026-028>030- 522-523. OR...Air Quality Alert until noon PDT Wednesday for ORZ044-502-503- 507.