textproduct: Pendleton

KEY MESSAGES

- Showers and isolated thunderstorms along the Cascade crest Today.

- Breezy winds in the lower elevations through Sunday.

- Another system will bring additional shower and thunderstorm chances Monday through Wednesday.

DISCUSSION

544 dm upper low pressure centered near 48.6N and 128W is forecast to be centered near the WA/BC border 24 hours for now. What this means for sensible weather is more clouds and cooler temperatures This afternoon as well as mountain showers for the Cascades and even some risk for isolated thunderstorms. Additionally breezy to windy surface westerlies across the Columbia Basin/Blue Mt Foothills and Columbia River Gorge, will be largely diurnally driven, weakening in the evening. This upper low becomes stretched/amplified and lifts northeast into Canada overnight into Sunday morning with a shortwave ridge, subsidence and dry conditions setting up for Sunday afternoon. A dry Sunday will be followed by another upper low to influence sensible weather again Monday and Tuesday with rain and thunderstorms, and even wetting rains across the mountain zones, (eastern mountains included this time) as the track of the upper low appears much farther south. Thursday and Friday will bring a rebound to more summer like temperatures in the 80s across the lower elevations.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

VFR conditions prevail through the period. Breezy winds at times at the TAF sites, with PROB30 chances of a slight shower at the DLS site later today. Not expecting any significant CIG or VIS issues.

FIRE WEATHER

Right now, only the WA fire wx zone (691) of the Columbia basin has fuels ready for red flag consideration. For Saturday afternoon, the combined probabilities for sub 30% RH and 15 mph or higher are in the 20% to locally 55-60% range, a bit short of red flag issuance confidence. Sunday is similar in nature in terms fire risk, with combined probabilities for critical fore weather running 10-40% across the eastern sections of WA691 and near the Columbia River. Probability of lighting is between 10 and 30 % on Cascade ridgetop from around noon through 7 pm.

Preliminary Point Temps/PoPs

PDT 66 40 70 46 / 0 0 0 20 ALW 67 45 70 50 / 0 0 0 0 PSC 71 42 75 48 / 10 0 0 10 YKM 68 40 74 48 / 20 10 0 10 HRI 69 41 73 47 / 0 0 0 20 ELN 60 36 66 42 / 40 10 0 20 RDM 62 28 69 42 / 0 0 0 20 LGD 63 38 67 42 / 0 10 0 0 GCD 65 36 68 41 / 0 10 0 0 DLS 66 43 72 51 / 40 30 0 20

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...None.