Sunrise 5:22 AM   Sunset 8:34 PM Moonrise 1:41 PM   Moonset 2:08 AM

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FXUS66 KPDT 172109 AFDPDT

Area Forecast Discussion National Weather Service Pendleton OR 209 PM PDT Fri May 17 2024

SHORT TERM
Tonight through Sunday night...A strong west- northwest flow aloft remains in the wake of an upper level shortwave that swept across the region late last night. Strong winds at the surface will continue in the lower elevations this evening and gradually decrease overnight as boundary layer winds decouple from winds aloft. The wind advisory for the Kittitas Valley is set to expire at 2 PM. The wind gusts for the next several hours will flirt around the advisory criteria near Ellensburg and Ryegrass Summit, and the plan for is to extend the advisory until 6 PM. From 6 PM until sunset, forecast will show gusts 35-45 mph based on the majority of the high resolution models. The tight cross Cascade gradient will remain through the night and into Saturday morning, therefore the eastern CR Gorge and some of the wind exposed gaps will remain breezy to windy through the night.

The forecast area will be under a stationary trough through the weekend. Another upper low initially over the BC coast will sag south across WA on Saturday with enhanced vorticity that will result in numerous showers along the northern half of the WA Cascades and a 20-30% chance of light showers over the northern Blue Mountains and foothills Saturday evening. The rest of the area will be dry and breezy with gusts 25-35 mph in many areas.
NBM probabilities of gusts > 35 mph on Saturday is minimal or zero with the exception of localized spots in the Kittitas Valley and the eastern CR Gorge.

Sunday and Sunday night will be met with a cool northerly flow aloft. After a chilly start to the morning, the afternoon will be partly to mostly cloudy with a 20-30% of orographic mountain showers and temperatures slightly below seasonal average. Snow levels will be around 4000 feet, and some of the mountain passes could see a light dusting of snow. Early morning temperatures are not forecast to fall below freezing in the zones currently in the growing season, but close with low in the mid-30s resulting in areas of frost in the Grande Ronde Valley, Simcoe Highlands and north central Oregon. Wister/85


LONG TERM
Monday 12Z(Monday) to Saturday 06Z(Friday night)...Not much has changed this work week with the NW flow aloft over PacNW left behind as the low over eastern Canada moves farther east while this trough pattern persists. Precip chances will be very low (<10%) at the low elevations however, chances of light mountain showers will increase as the front passes over PacNW (20-40%) starting Tuesday thus bringing orographic lift into the moisture- starved trough. This can induce thunderstorms across Wallowa County for Monday through Wednesday but with low chances (<20%) due to weak instability and less moisture from the dry airmass.

QPF amounts remain very light at the low elevations whereas Cascades increase up to 0.25 inch Tuesday including the Blues for Wednesday and Thursday before decreasing Friday. Gusty winds continues at around 20-30kts Tuesday into Wednesday night mainly along Simcoe Highlands, OR Columbia Basin, Kittitas and Yakima Valley with strong surface pressure gradient due to the front passing. The NBM probabilities of wind gusts >=22 mph shows high chances greater than 70%, but 40-60% over Ochoco-John Day Highlands.

Good agreement overall with the models and ensembles on trough pattern with light mountain showers Thursday and Friday. Though, 23% of total cluster members favor the low over PacNW as does the GFS model whereas other models show the low moving east from the forecast area after Wednesday but no major differences in shower chances. High temperatures will be in the 60-70s at the low elevations with 50s-60s at the mountains. Snow levels will increase to about 5000ft or higher this week. Feaster/97



AVIATION
18Z TAFS (previous discussion)...VFR conditions remains favorable for the TAF period. All sites currently have clear skies until high clouds starts occurring for some this evening, but clears up at KPDT Saturday morning. Wind gusts are today's major concern at 20-30kts with sustained winds at 12-20kts until decreasing this evening for most sites, except for KDLS at 14Z Saturday. Feaster/97



PRELIMINARY POINT TEMPS/POPS
PDT 39 67 39 63 / 0 0 10 0 ALW 44 70 44 66 / 0 0 20 10 PSC 46 72 45 71 / 0 0 10 0 YKM 39 69 38 69 / 0 0 0 0 HRI 44 71 43 70 / 0 0 0 0 ELN 41 63 40 63 / 0 10 0 0 RDM 35 66 33 58 / 0 0 0 0 LGD 36 66 38 58 / 0 0 10 10 GCD 36 68 36 59 / 0 0 0 0 DLS 44 67 45 66 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES
OR...None.
WA...Wind Advisory until 6 PM PDT this evening for WAZ026.

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