Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
417 FXUS66 KPDT 302330 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 430 PM PDT Mon Jun 30 2025 .Updated Aviation Discussion. .AVIATION...00Z TAFS...VFR conditions currently across all sites, which will stay the course through the period. Winds will stay light and below 10 kts for most sites, with the exception of KRDM/KBDN/KDLS experiencing gusts up to 20-25 kts toward the end of the period. KRDM/KBDN will also experience gusts up to 20 kts late this afternoon before dissipating this evening. SCT-BKN ceilings of 20-25kft will build in this evening and overnight as a system approaching from the south. 75 && .PREV DISCUSSION... /issued 156 PM PDT Mon Jun 30 2025/ SHORT TERM...Today through Wednesday...Heat returns to the forecast area as the PacNW finds itself wedged between high pressure ridging to the north and a cutoff low to the south over California. Such a setup is ripe for not only hot temperatures through Tuesday, but also for elevated thunderstorms for central Oregon, spreading eastward through Wednesday as the northeastward progression of this low amplifies SW flow and thus moisture advection over the forecast area. Not much change in heat headlines, as Heat Advisories remain in effect for the Basin, Gorge, Yakima/Kittitas Valleys, and north central Oregon. Tuesday continues to look like the hottest day, with much of the Basin expected to eclipse the century mark on Tuesday afternoon. Once high pressure is nudged aside heading into Wednesday, temperatures are expected to trend toward more seasonable readings. Keeping an eye on the shower and thunderstorm threat for central Oregon starting this evening as a result of SW flow becoming more prominent over the region. Latest HREF guidance generally keeps convective activity south of the forecast area tonight, before ramping up tomorrow afternoon and spreading as far north as the southern Blues and as far east as the John Day Valley. Bullseye currently appears to be Deschutes and Crook Counties, at least for our forecast area. PWATs are on the higher end (0.7-0.9 inches) owing to strong SW flow aloft, and a slower storm motion would suggest more of a wetting rain potential, but with convective parameters as supportive of convection as they are (plentiful mid- level moisture with MUCAPEs reaching up to 1000 J/kg), have elected to err on the side of caution and issue a Red Flag Warning for at least one central Oregon zone (OR700) for dry lightning. QPF falls off quite a bit to the north of this "bullseye," so am not confident enough in widespread wetting rains to completely negate the dry lightning effect. Confidence in wetting rains increases for storms closer to the Cascades. On Wednesday, winds increase as high pressure breaks down. Temps cool, but with the boundary layer still dry from Tuesday`s heat, winds have the potential to combine with low RHs in the teens to create critical fire weather conditions. Have opted to issue a Fire Weather Watch for the Washington Columbia Basin and Kittitas Valley for Wednesday as a result. RHs do seem high enough to preclude critical conditions in adjacent zones, and winds/RHs are admittedly borderline in the watch zones, but the overall setup does at least support elevated fire spread concerns. Will see how models evolve with regards to the RH and winds on Wednesday and adjust the Watch accordingly. Evans/74 LONG TERM...Thursday through Monday...Ensembles suggest the potential for another shortwave trough to cross through the PacNW on Thursday, making for another chance for showers and isolated thunderstorms across mainly the eastern mountains. The thunderstorm risk will be downplayed, however, due to weakening instability, stemming from lower lapse rates as this relatively progressive synoptic pattern shaping up helps stabilize the atmosphere to a degree. Ensemble clusters generally suggest a benign pattern heading into the Holiday weekend, split between a weak zonal or SW pattern, but neither strong enough to produce shower chances for either the Cascades or eastern mountains. Expect generally seasonable temperatures, with winds slackening after Thursday as the progressive nature of the pattern lightens up. Evans/74 && .PRELIMINARY POINT TEMPS/POPS... PDT 64 100 67 93 / 0 0 10 10 ALW 68 99 70 92 / 0 0 10 20 PSC 63 102 66 96 / 0 0 0 10 YKM 65 100 65 94 / 0 0 0 0 HRI 63 102 68 95 / 0 0 10 10 ELN 65 99 65 87 / 0 0 0 0 RDM 57 96 55 87 / 0 10 20 10 LGD 60 96 63 89 / 0 0 10 20 GCD 61 97 60 90 / 0 10 30 20 DLS 68 98 65 85 / 0 0 10 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Heat Advisory until 9 PM PDT Tuesday for ORZ041-044-507-508-510. Red Flag Warning from 2 PM to 9 PM PDT Tuesday for ORZ700. WA...Heat Advisory until 9 PM PDT Tuesday for WAZ024-026>029-521. Fire Weather Watch from Wednesday afternoon through Wednesday evening for WAZ690-691. && $$ SHORT TERM...74 LONG TERM....74 AVIATION...75