Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
403 FXUS66 KPDT 292046 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 146 PM PDT Sun Jun 29 2025 .SHORT TERM...Today through Tuesday night...Quiet weather is forecast for the remainder of today, tonight, and much of Monday as an upper-level ridge of high pressure builds into the Pacific Northwest. The ridge will facilitate light offshore flow into Monday, and more notably, warming temperatures. Ensemble NWP is very confident (95% or greater) that the aforementioned upper-level ridge will amplify through Monday and remain in place through Tuesday, leading to hot conditions. Meanwhile, an upper-level closed low will continue to develop off the central California coast, setting the stage for convection in southern/eastern Oregon Monday and Tuesday. CAMs suggest the bulk of the convective activity Monday will be across south-central Oregon with limited extension northward into central Oregon, perhaps due to weak forcing aloft. That said, have maintained a slight chance (15%) of thunderstorms in the forecast for the east slopes of the Oregon Cascades in Deschutes County and also for areas east into the Ochocos-John Day Highlands. Confidence is low (<50%) that thunder will accompany isolated to scattered showers in central and eastern Oregon Monday night, so have omitted mention in the forecast. Should mention that, due to ample forecast DCAPE of 1000-1500 J/kg per HREF and REFS soundings, convective outflow has the potential to generate gusts in excess of 50 mph in central Oregon Monday afternoon, and the SPC has a Marginal (level 1 of 5) risk of severe thunderstorms placed just south of Deschutes County. Convective potential looks better Tuesday across the Blue Mountains region where a slight chance (15-24%) to chance (25-30%) of showers and thunderstorms has been included due to the combination of sufficient mid-level moisture, instability, and modest upper-level forcing. Anticipated warming under the upper-level ridge has prompted the issuance of Heat Advisories for most of our lower-elevation areas across northern Oregon and south-central Washington for Monday through Tuesday. Widespread Moderate (level 2 of 4) to Major (level 3 of 4) HeatRisk is on tap due to forecast high temperatures of 91-103 degrees and overnight low temperatures of 61-73 degrees. Will note there is some uncertainty in high and low temperatures Tuesday and Wednesday due to potential cloud cover -- convective debris or otherwise. Plunkett/86 && .LONG TERM...Wednesday through Saturday...Wednesday through Friday, analysis of ensemble clusters indicates there is more uncertainty (timing and amplitude of 500-hPa heights) in pattern details, but guidance is strongly suggesting one or more shortwaves embedded within broadly southwesterly flow aloft. This pattern favors showers and thunderstorms for the Blue Mountains region, so have added a slight chance (15%) of thunder each afternoon. Otherwise, breezy to windy westerly winds are favored through the Cascade gaps Wednesday through Thursday. Confidence in surface moisture (dew point and relative humidity) is still low (<30%) due to aforementioned uncertainty in pattern details so will hold off on mentioning potential for any fire weather highlights. Plunkett/86 && .AVIATION...18Z TAFs...VFR conditions are very likely (>95% chance) through the period for all sites. Clear skies and mostly light (sustained at 10 kts or less), diurnally and terrain-driven winds are forecast. Will note gust potential of 14-18 kts in the afternoon and evening, mainly at BDN/RDM. Plunkett/86 && .PRELIMINARY POINT TEMPS/POPS... PDT 55 99 66 101 / 0 0 0 10 ALW 60 96 69 100 / 0 0 0 10 PSC 58 100 63 103 / 0 0 0 0 YKM 61 98 66 100 / 0 0 0 0 HRI 58 100 65 103 / 0 0 0 10 ELN 59 98 66 98 / 0 0 0 0 RDM 51 96 58 95 / 0 0 10 20 LGD 56 94 62 97 / 0 0 0 10 GCD 56 97 61 97 / 0 0 10 20 DLS 64 100 68 97 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Heat Advisory from 9 AM Monday to 9 PM PDT Tuesday for ORZ041- 044-507-508-510. WA...Heat Advisory from 9 AM Monday to 9 PM PDT Tuesday for WAZ024- 026>029-521. && $$ SHORT TERM...86 LONG TERM....86 AVIATION...86