Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
341 FXUS66 KPDT 050459 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 959 PM PDT Fri Jul 4 2025 Updated Aviation Discussion .AVIATION...06Z TAFS...VFR conditions to prevail through the period. CIGs of generally bkn-ovc AOA 12kft AGL will prevail through tonight, with clearing skies or high level few-sct decks for most of tomorrow. Winds will generally be 12kts or less through the period, except at site DLS where winds 12-17kts with gusts to around 25kts will redevelop around 17Z and persist through the end of the period. Lawhorn/82 PREV DISCUSSION... /issued 201 PM PDT Fri Jul 4 2025/ .SHORT TERM...This afternoon through Sunday...An upper-level low- pressure system is moving onshore into western Oregon this afternoon, inducing widespread cloudiness and precipitation over the forecast area. The first of two shortwaves embedded within the broader low is continuing to move inland across eastern Oregon, western Idaho, and southeast Washington. Activity with this wave has developed into a weak deformation band and is suppressing afternoon temperatures. Meanwhile, clearing across central Oregon and the Ochoco-John Day Highlands early afternoon has facilitated modest (250-500 J/kg) surface-based CAPE. The second shortwave is moving into southwest Oregon and is progged to propagate in inland over south-central and eastern Oregon through the remainder of the afternoon and evening. Coupled with falling heights aloft as the main upper low moves overhead, this should aid additional thunderstorm development primarily for Deschutes, Crook, Wheeler, and Grant counties. Of note, 12Z HREF neighborhood probabilities are highlighting up to a 70% chance of 3-hr precipitation exceeding 1 inch over last year`s burn scars in the Ochoco-John Day Highlands. The main burn scars of concern include those associated with the Wiley Flat, Rail Ridge, Crazy Creek, and Falls fires. After collaboration with BOI, have issued a Flash Flood Watch for the aforementioned burn scars, valid through 8PM PDT. Quieter weather will return Saturday and Sunday as the low exits to the east and drier zonal flow aloft moves overhead. Plunkett/86 .LONG TERM...Monday through Thursday...Confidence is increasing in warm to hot weather Monday through Thursday as an upper-level ridge of high pressure builds over the Pacific Northwest. That said, ensemble clusters do depict some differences in the 500-hPa height field over the region, most notably the evolution of a closed low that all clusters show off the NW California coast Monday. Ensemble mean 500-hPa heights and vorticity show the aforementioned low tracking inland across southern Oregon and the northern Great Basin late Tuesday through Wednesday. Farther north across southern BC, roughly half of ensemble members show a shortwave trough propagating inland, significantly reducing the amplitude of the ridge over the Pacific Northwest. The track and timing of the closed low and shortwave will modulate temperatures as well as shower and thunderstorms chances. Probabilities of showers and thunderstorms are currently too low (<10%) to have in the forecast. Forecast HeatRisk ranges from Moderate (level 2 of 4) on Monday and Wednesday to Major (level 3 of 4) on Tuesday. This level of heat would support Heat Advisories for the Yakima/Kittitas valleys, lower Columbia Basin, and foothills of the northern Blue Mountains on Tuesday. Plunkett/86 .FIRE WEATHER...Through this evening, a low-pressure system moving over the Pacific Northwest will facilitate widespread precipitation chances, highest for Oregon. Additionally, a chance of thunderstorms is forecast for central Oregon and the Blue Mountains. Chances of wetting rain through the evening are medium- high (50-80 percent for the Blue Mountains) with low-medium chances (30-60 percent) for the rest of central and eastern Oregon. No Red Flag Warnings have been issued due to the anticipated wetting rain, but frequent cloud-to-ground lightning is expected. Thunderstorms will be capable of producing locally heavy rainfall, small hail, and strong, gusty outflow winds in excess of 60 mph across southeast Deschutes, Crook, and Grant counties this afternoon and evening. Plunkett/86 && .PRELIMINARY POINT TEMPS/POPS... PDT 57 86 56 91 / 20 0 0 0 ALW 61 86 60 90 / 10 0 0 0 PSC 59 89 56 92 / 10 0 0 0 YKM 59 88 57 91 / 10 0 0 0 HRI 59 89 57 93 / 10 0 0 0 ELN 58 85 57 88 / 10 0 0 0 RDM 43 82 45 89 / 20 0 0 0 LGD 52 81 53 87 / 30 0 0 0 GCD 47 82 51 89 / 60 0 0 0 DLS 56 84 57 90 / 10 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...86 LONG TERM....86 AVIATION...82