394 FXUS66 KPDT 172110 AFDPDTArea Forecast Discussion National Weather Service Pendleton OR 210 PM PDT Wed Sep 17 2025
.DISCUSSION...Today through Friday: Quiet, benign weather prevails with warm, dry conditions as the high pressure system gradually moves eastward. However, the thermal trough remains persistent. The approaching upper trough will last tomorrow into Friday, but with both days remaining dry. This weather pattern will keep the high temperatures in the 70s and 80s with a 60-90% probability of reaching in the mid to high 80s. Daytime RHs will remain in the 30s today for lower elevations, though with John Day Highlands and Basin in the mid-teens and low 20s before improving tomorrow onwards.
Saturday through Wednesday: The deterministic models and ensembles do show an agreement for Saturday with the PacNW in between a cutoff low extended across CA coast and an upper ridge over British Columbia. The ECMWF favors light moisture over the eastern mountains Saturday around 5pm from an potential upslope flow, but the GFS has the Cascades with light precip later on that day as well. Overall, this raises a challenge in forecasting the precip due to the timing difference with the frontal system.
However with this pattern and the associated thermal trough, gusty west winds could develop along the Cascade Gaps at 20-30 mph. This may potentially promote elevated fire weather conditions for nearby wildfires. Confidence is low (
NWS PDT Office Area Forecast Discussion