Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
609 FXUS66 KPDT 281749 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1049 AM PDT Sat Jun 28 2025 .AVIATION...18Z TAFs...VFR conditions are forecast through the period for all TAF sites. FEW-BKN stratocumulus, mainly across central Oregon, are expected to dissipate through the day with SKC for all sites by tonight. Diurnally and terrain-driven winds are forecast through the period, strongest this afternoon and evening for DLS/BDN/RDM/YKM. Plunkett/86 && .PREV DISCUSSION... /issued 427 PM PDT Fri Jun 27 2025/ SHORT TERM...Tonight through Sunday...Satellite imagery this early afternoon shows cumulus fields developing across portions of northeast OR and southeast WA as an upper trough axis passes over the region. Otherwise, surface observations indicate breezy conditions across the lower elevations. A broad, shallow upper trough will continue to sit over the PacNW today with shower activity confined to the WA Cascade crest through this evening. Breezy winds will also continue through the Cascade gaps into the Columbia Basin today. Tomorrow the upper trough will be pushed east as upper level ridging builds offshore. Breezy winds will continue through the Cascade gaps for Saturday, otherwise conditions will remain dry with locally breezy winds in the Columbia Basin. Upper level ridging will move inland and strengthen over the region Sunday, resulting in afternoon temperatures in the lower to mid 90s developing in the lower elevations and mid 70s to 80s in the mountains. Lawhorn/82 LONG TERM...Monday through Friday...Ensemble guidance in good agreement that upper level ridging will persist across the PacNW through Tuesday morning, before slowly moving east of the northern Rockies. During this time, afternoon temperatures will continue to warm across the region, with high confidence (80-90%) of widespread mid to upper 90s developing both Monday and Tuesday leading to widespread moderate and pockets of Major HeatRisk developing; confidence is mod-high (60-80%) in temperatures reaching or just exceeding the 100 degree mark in portions of the Columbia and John Day Basins, leading to areas of Major HeatRisk in these areas. Will continue to monitor for the need of heat highlights for Monday and Tuesday. Otherwise, as the upper ridge pushes east on Tuesday, the cross-Cascade surface pressure gradient will strengthen, resulting in breezy winds returning through the Cascade gaps and into portions of the Columbia Basin. Ensemble guidance is also in good agreement that a broad upper low that develops off the CA coast will help facilitate a monsoonal moisture push into OR both Monday and Tuesday. Combined with increasing surface instability and modest mid level Theta-E lapse rates, slight chances (10-25%) of thunderstorms will develop across central OR and the eastern OR mountains in the afternoons and evenings. Wednesday through Friday, ensemble cluster solutions are in agreement of upper level troughing developing across the PacNW, though differences increase in its position and strength. That said, ensemble cluster solutions favor another round of a slight chance (~15%) of thunderstorms across the eastern mountains Wednesday afternoon with dry conditions Thursday into Friday. While confidence is moderate (60-70%) that temperatures will cool across the region, there is higher uncertainty in how cool it will get owing to the disagreement on the strength of the upper trough. At this time, the NBM deterministic forecast is forecasting high temperatures in the mid 80s to mid 90s across the lower elevations and 70s to mid 80s mountains each day (confidence 25-40%). Otherwise, mod-high confidence (60-80%) that breezy winds will continue through the Cascade gaps through the end of next week. Lawhorn/82 && .PRELIMINARY POINT TEMPS/POPS... PDT 85 55 92 60 / 0 0 0 0 ALW 83 59 90 64 / 0 0 0 0 PSC 87 55 93 59 / 0 0 0 0 YKM 85 55 91 61 / 0 0 0 0 HRI 87 55 94 59 / 0 0 0 0 ELN 82 55 91 60 / 0 0 0 0 RDM 82 45 90 52 / 0 0 0 0 LGD 79 51 87 56 / 0 0 0 0 GCD 82 50 91 57 / 0 0 0 0 DLS 84 59 94 64 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...82 LONG TERM....82 AVIATION...86