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 /06Z TAFS THROUGH 06Z TUESDAY/

Ceilings near but not over the PDT ALW terminals due to cool moist boundary layer as the rains end and the fact that the HREF is printing low vsbys in the adjacent foothills. Guidance, both climate and HREF keep the terminal vicinities clear with light south to southwest winds overnight. NO chances for impacts elsewhere. Surface winds will increase marginally to 10 to 15 knots through the Gorge/Blue Mt Foothills terminals (DLS/PDT/PSC/ALW) Monday afternoon with gusts commonly in the 20 to 25 knot range).

Preliminary Point Temps/PoPs

PDT 47 71 42 75 / 20 10 0 0 ALW 51 73 49 77 / 40 20 0 0 PSC 50 76 46 79 / 10 0 0 0 YKM 52 76 48 78 / 10 0 0 0 HRI 50 74 45 78 / 10 0 0 0 ELN 48 71 45 77 / 20 0 0 0 RDM 37 68 38 75 / 20 0 0 0 LGD 45 68 42 74 / 90 20 10 0 GCD 44 67 41 76 / 90 10 0 0 DLS 53 74 51 80 / 30 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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