768 FXUS66 KPDT 211053 AFDPDTArea Forecast Discussion National Weather Service Pendleton OR 353 AM PDT Sun Sep 21 2025
.OVERNIGHT UPDATE...Radar is showing a few scattered showers over the area this early morning with ground observations showing a few of the higher terrain areas along the Blues receiving some accumulated rain amounts of up to 0.01 while other areas like here in PDT receiving a trace. Other than that, no real change from the current forecast. The upper level trough will continue to move in from the NW bringing increased chances of rain through the morning through early afternoon before teetering off in the afternoon with 20-40% probabilities of up to 0.03 inches of accumulation. Winds will also increase to between 20-25 mph through the Gorge and along the Horse Heaven Hills (45-70%). With that cold front, temperatures behind the passage will be between 5 to 10 degrees cooler than seasonal average with most areas seeing upper 60s to low 70s with a few isolated locations within the Columbia Basin seeing mid 70s (80%). Also, this cold front will be followed by a slot of cold and dry air which will cause overnight temperatures to dip to near freezing 32-36 degrees (50-80%) in lower central OR through the eastern mountains and into Wallowa Valley. Confidence in reaching below freezing is low to moderate at this time (30-60%). Bennese/90
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.UPDATED AVIATION...VFR conditions forecasted to prevail through the period. A cold front passage tonight through tomorrow will bring rain impacts to all sites through 2 PM with slight chances (15%) for BDN/RDM and chance(20-40%) rain for YKM/PDT/PSC/DLS/ALW. Winds will also see an increase through all sites seeing winds between 10-20 kts with gusts to 20-30 kts beginning at 13Z for DLS/BDN, and after 15Z at the remaining sites. Bennese/90
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PREV DISCUSSION... /issued 156 PM PDT Sat Sep 20 2025/
DISCUSSION...Satellite imagery reveals multiple features of interest in the Pacific. A closed low centered off the coast of central California is advecting remnants of tropical moisture northward into the Blue Mountains region, leading to PWATs of 150-200% of normal. To the northwest, a closed low is churning in the Gulf of Alaska, and water vapor imagery shows a shortwave diving southeast towards the Pacific Northwest. Ahead of the shortwave, a frontal boundary is draped from Vancouver Island southwest into the Pacific.
Today, there is a slight chance (10-15%) of isolated showers and thunderstorms across the Blue Mountains, roughly from the Bend metro area eastward. Cross-Cascade pressure gradients will drive breezy winds through the Cascade gaps into wind-prone areas of the Columbia Basin today. While some areas will approach Red Flag thresholds for wind and low relative humidity, confidence was too low (
NWS PDT Office Area Forecast Discussion