textproduct: Pendleton

KEY MESSAGES

- Shower and thunderstorm chances through this evening, with decreasing chances on Monday.

- Dry weather through much of the week with seasonable temperatures. - Potential for another upper trough and precipitation next weekend.

DISCUSSION

The persistent upper low that has been over the Pacific Northwest will begin to move eastward tonight and will be well east of the region on Monday. However, some troughing will remain over the area and will keep unsettled conditions, mainly over the eastern Oregon mountains on Monday, with everywhere else remaining dry.

By Tuesday, and through much of the week, the area will be under a split flow regime, with a more westerly flow moving in by Thursday.

On Friday, another upper low will drop down from the northwest, and bring another chances of showers, and possibly some thunderstorms, mainly to the mountains. This low will cross the region on Saturday and exit on Sunday. Unlike the current low, this looks to be a fast moving progressive low.

Latest radar showed isolated to scattered showers. Satellite imagery showed abundant cloud cover and many areas were struggling in the 50s and lower 60s, though the Columbia Basin was close to 70 degrees. Cloud cover is affecting thunderstorm development, but if we are able to get some sufficient breaks later this afternoon, the most likely areas for thunderstorm development would be from the northern Blue Mountains eastward.

In areas of heavy rain, the could be 0.25 to 0.50 inches, but most places will see less than 0.25 inches.

Monday will see breezy winds, in the 25 to 30 mph range, possibly as high as 35 mph across the Cascade Gaps, Kittitas Valley, Simcoe Highlands and the Columbia Basin and Gorge.

Another breezy period will be Thursday across the same areas in advance of the next trough winds will be similar (possibly a bit higher), though RH values will be lower on Thursday. Areal coverage of wind gusts are a bit more on Thursday while probabilities of wind gusts >= 25 mph >80 percent both days.

High temperatures will remain 10 to 15 degrees below normal on Labor day before rising to near seasonal normals for much of the week. Highs will ten drop below normal again Friday and Saturday as the next trough moves through. the ECMWF EFI has 0.8 to 0.9 below normal for Monday across mainly central and eastern portions of Oregon.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Periods of light to moderate rain showers continue through the next few hours. Rain will dry out as we head into the later afternoon to early evening hours. Guidance is picking up wind getting breezier in DLS and ALW tomorrow morning with max wind gusts of 15 to 25 knots. For the rest of the today, VFR conditions prevail but there has been some reported MVFR conditions temporarily lasting which I expect to not last long as the precip moves out of the area. There is still a low probability (10 to 20 percent) of some MVFR conditions moving in and out at the TAF sites.

Preliminary Point Temps/PoPs

PDT 47 71 42 76 / 20 20 0 0 ALW 51 73 49 78 / 50 30 0 0 PSC 50 77 48 80 / 10 20 0 0 YKM 52 77 51 79 / 20 0 0 0 HRI 50 75 48 79 / 10 20 0 0 ELN 48 71 45 77 / 20 0 0 0 RDM 37 68 37 75 / 30 0 0 0 LGD 45 68 41 74 / 90 40 10 0 GCD 44 67 41 76 / 70 10 0 0 DLS 53 75 51 80 / 20 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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