textproduct: Pendleton

KEY MESSAGES

- An upper level low will move onshore Thursday and remain over the Pacific Northwest through much of the weekend.

- Widespread shower chances through early Thursday, with isolated thunderstorm chances each afternoon through Friday. Low (<30) shower and thunderstorm chances, mainly over the mountains through the holiday weekend.

- Below normal temperatures through the remainder of the week and into the weekend.

DISCUSSION

An area of low pressure off the British Columbia coast will move southeastward and inland over Washington and Oregon on Thursday. This upper low will keep the weather unsettled over the next few days.

As this low approaches, strong southerly flow ahead of it will bring a fairly widespread rainfall across the region this evening into early Thursday. Most locations, except the COlumbia Basin and possibly central Oregon should get wetting rain and the mountain locations should get significantly more, with mountain locations receiving at least 0.25 inches and possibly 0.50 inches or more. As the low moves across the region Thursday and Friday, the precipitation will largely be confined to the mountains, where additional wetting rains are possible. The highest rain total look to be for areas from the northern Blue Mountains eastward. With instability from the upper low in place, isolated (<20%) thunderstorms are possible, mainly over the mountains. Over the holiday weekend, precipitation chances still exist but will be lower, generally (<30%).

Finally, by Monday, the low begins to move eastward and drier weather will move in from later Monday through the midweek period.

Winds will also gust 20 to 30 mph this afternoon and evening as the low approaches.

High temperatures will mainly be in the 60s and 70s through the weekend. This is 7 to 10 degrees below normal on average. Lows will mainly be in the 40s, with some 30s as well, which are also about 7 to 10 degrees below normal. The ECMWF EFI indicates some areas mainly in central Oregon where departures are below normal are greater than the 90th percentile with some locations even in the 95th percentile below normal for high temperatures. By midweek, temperatures return closer to normal.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Upper low moving into the region over the next 24 hours will bring a changeover to rain and isolated thunderstorms in the first 12-18 hours of the TAF period and a clearing for lower elevations later Thursday. Most of the cloud ceilings will be in the the MVFR range at word, mainly in central Oregon RDM/BDN and YKM, where lower elevation terminals will have higher cigs in the VFR category. Rain rates will be light enough to maintain visibilities above the IFR.

Preliminary Point Temps/PoPs

PDT 45 68 42 67 / 90 20 30 30 ALW 49 68 47 68 / 100 30 40 40 PSC 47 72 46 72 / 80 0 10 30 YKM 47 70 48 71 / 40 10 10 20 HRI 47 71 46 71 / 90 0 20 20 ELN 43 66 42 67 / 60 30 20 40 RDM 37 64 35 63 / 80 20 50 50 LGD 46 65 42 65 / 90 70 80 70 GCD 44 63 41 65 / 100 70 80 40 DLS 50 69 50 71 / 80 30 30 30

PDT WATCHES/WARNINGS/ADVISORIES

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