Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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596 FXUS66 KPDT 081056 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 207 AM PDT Wed May 8 2024 .SHORT TERM...Today through Friday night...No major weather concerns are anticipated in the short term period. In fact, it will be quiet. The forecast area will be between a building ridge offshore and a large upper low to the east today, leaving us in a north-northeast flow aloft. There is a slight chance (20%) of light showers in far eastern Wallowa County today associated with wrap around moisture, but the upper low is way east over the northern Plains that any showers will be isolated. The offshore ridge will amplify and shift to the east while a closed low sets up over the four corner states, resulting in a rex block across western Canada and the western U.S. for the remainder of the short term period. All that means for WA/OR is continued dry with a warming trend. The inverted surface thermal trough will remain west of the Cascades Thursday through Friday. If the thermal trough was farther east, we would anticipate a major warm up. Afternoon highs on Friday will be around 10-15 degrees above seasonal average, but not record-breaking temperatures. Wister/85 .LONG TERM...Saturday through Wednesday...The long term will be characterized by an upper level high pressure ridge to start. Sunday night into Monday, a few shortwaves will attempt to make their way across the region beginning Monday bringing with it slightly cooler temperatures and minimal mountain precipitation. Saturday through Sunday afternoon models are in firm agreement with the upper level ridge well overhead. Clusters also show decent agreement with the upper level ridge, primary difference being with the amplitude. Dry and warming conditions will dominate with some areas in the forecast region seeing temperatures nearing the 90s. Raw ensembles show over 90% probabilities that the Columbia Basin, the Gorge and portions of the foothills of the Blues will see temperatures over 85 degrees Saturday decreasing in area to primarily the Basin Sunday. Temperatures in the mid elevations will see 70-80% probabilities of upper 70s to low 80s while the higher elevations will see 60-70% chances of high 60s to low 70s. EFI shows that these temperatures are above normal for this time of the year with the signal strongest over the Cascades and the Columbia Basin. Sunday night through Wednesday models show a ripple of shortwaves making their way across the forecast region. However, clusters show a bit of a discrepancy with how these shortwaves will affect the ridge. If the ridge remains strongly amplified, little will come of the shortwaves. If the ridge weakens in any way, the upper level shortwaves could be strong enough to flatten the ridge slightly bringing a more westerly flow across the region. With this, the NBM ensembles have taken almost a middle ground with the models. Monday morning there is a less than 20% probability of 0.01 inches of precipitation expected along the highest points of the WA Cascades. As the shortwave continues across the region, probabilities only increase to under 25%. However, due to the shift to a more westerly flow, winds are expected to pick up primarily through the Cascade Gaps. 50-70% of the raw ensembles show winds of 20-25 mph through the Gorge, foothills of the Blues, and Kittitas and Yakima Valleys. EFI shows a steady decline back towards seasonal average by Wednesday due to the flattening of the ridge and the incoming shortwaves. However, 70-80% of the raw ensembles keep the Basin, adjacent valleys, the Gorge and the foothills in the mid to upper 70s, mid elevations in the low to mid 70s and the higher elevations in the low to mid 50s. Bennese/90 && .AVIATION...12Z TAFs...Primary interest this period will be the winds. Winds will be mostly terrain driven between 05-12 kts with RDM/BDN seeing gusts to 20 kts through 01-03Z. Otherwise, VFR conditions will dominate the period with mostly clear skies. Bennese/90 && .PRELIMINARY POINT TEMPS/POPS... PDT 62 40 73 46 / 0 0 0 0 ALW 64 43 78 49 / 0 0 0 0 PSC 72 45 81 52 / 0 0 0 0 YKM 72 42 80 48 / 0 0 0 0 HRI 69 43 79 49 / 0 0 0 0 ELN 69 43 78 49 / 0 0 0 0 RDM 60 34 71 41 / 0 0 0 0 LGD 56 38 71 44 / 0 0 0 0 GCD 57 33 72 42 / 0 0 0 0 DLS 71 47 81 52 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...85 LONG TERM....90 AVIATION...82