


Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
565 FXUS66 KPDT 182340 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 440 PM PDT Fri Jul 18 2025 .Updated Aviation Discussion... .AVIATION...00Z TAFS...VFR conditions currently across all sites, which will stay the course through the period. The main concerns revolve around elevated winds across all sites due to a passing cold front. Sustained winds of 12-20 kts with gusts up to 30 kts will be possible, with highest winds expected at KDLS/KPDT through this evening. Winds will stay breezy through the period for most sites, with the exception of KYKM/KPSC. 20-25kft SCT-BKN ceilings will accompany the cold front this evening, dissipating overnight but returning at KDLS/KYKM/KALW/KPSC late in the period. 75 && .PREV DISCUSSION... /issued 203 PM PDT Fri Jul 18 2025/ DISCUSSION...Tonight through Friday. Key Messages... - Critical fire weather conditions this afternoon and evening with hot, dry, and windy conditions, except across northeast OR and the upper east slopes of the WA Cascades - Heightened fire weather conditions Saturday across the Lower Basin and Kittitas Valley - Slight chance of isolated thunderstorms over the WA Cascades and eastern mountains Monday - Cooler, near average Sunday into early next week with highs rebounding above average Wednesday onward with a drying trend late next week. Latest water vapor imagery shows a shortwave trough descending into WA with a low over British Columbia in tandem with increasing mid-level flow spreading into south central WA. Latest day cloud phase imagery shows largely clear skies outside south central WA downstream of approaching high clouds. The shortwave trough will continue dropping southeastward with its attendant dry cold front crossing the area early tonight. Increasing W-SW winds ahead of the front will be reinforced with the strongest winds and gusts expected 5-11 pm today with minimum RH 10-20% common across the lower elevations. Increased confidence, 80% or higher, with gusts greater than 25 mph across the Lower Basin, eastern Columbia Gorge, south central WA; highest gusts spilling out of the eastern gorge into north central OR and the Kittitas valley wherein daily peak gusts of 39 mph or more are anticipated (80-100% chance). Winds will then subside and lessen gradually overnight. Despite cooler air mass post-frontal, a favorable overlap of breezy winds and afternoon humidity is expected again as the upper low sags to the southern BC-Alberta border. Of which, elevated to locally critical fire weather conditions are expected across a portion of the eastern Gorge into northern Sherman, Gilliam, Morrow counties and Kittitas valley. Highs will drop 4-8 degrees tomorrow from today. Meantime, afternoon RHs will be near to slightly above seen today across south central WA owing to modest isentropic descent and drying via 305-310 theta surfaces as seen among deterministic guidance. Breezy to gusty winds still expected with modest pressure differences seen cross-Cascades though flow aloft not as strong as this afternoon and evening. Quiescent fire weather conditions Sunday-Tuesday with respect to humidity and winds owing to a relaxed pressure gradient and more BL moisture. With the upstream amplification of an upper ridge in the eastern North Pacific and Gulf of Alaska late Saturday-Sunday, mean mid-level troughing will take hold downstream over the region Sunday-Tuesday. This with increased moisture and marginal instability with gudience supporting robust precipitable waters in place for this time of year will promote low chances, 10-25%, for thunderstorms Monday across the eastern mountains and WA Cascades, including chances for wetting rain as high as 30%. This threat will then shift farther east Tuesday, and be confined to the far eastern mountains. Looking onward, ensemble guidance favors a building upper-level ridge Wednesday-Thursday over the eastern CONUS with weak troughing/zonal westerly flow over the region. Meantime, clustering scenarios lean towards a warming and drying trend by Friday in response to the most likely outcome of a southwest flow regime taking hold by Friday (~75%). As such, drying and warming trend is anticipated with highs reading few-several degrees above average Wednesday-Friday. This scenario could result in elevated fire weather concerns. Of which, latest hot-dry-windy reflects this with GEFS showing increasing chance of exceeding the 75th and 90th percentile Wednesday and Thursday across the Lower Columbia Basin and south central WA. && .PRELIMINARY POINT TEMPS/POPS... PDT 61 88 59 84 / 0 0 0 0 ALW 65 88 62 83 / 0 0 0 0 PSC 60 91 58 86 / 0 0 0 0 YKM 59 88 57 85 / 0 0 0 0 HRI 61 90 60 86 / 0 0 0 0 ELN 57 84 57 83 / 0 0 0 0 RDM 52 85 49 83 / 0 0 0 0 LGD 57 85 56 83 / 0 0 0 0 GCD 56 87 53 85 / 0 0 0 0 DLS 61 84 61 82 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning until 10 PM PDT this evening for ORZ691-696>698- 700-701-703. WA...Red Flag Warning until 10 PM PDT this evening for WAZ690-691. && $$ SHORT TERM...80 LONG TERM....80 AVIATION...75