Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
663 FXUS66 KPDT 301726 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1026 AM PDT Mon Jun 30 2025 Updated Aviation Discussion .AVIATION...18z TAFs...VFR conditions expected. Skies will remain clear during the day with light, terrain-driven winds less than 12 kts, except for some gusts up to 20 kts for BDN and RDM. Mid clouds sct-bkn will then build in late this evening and overnight for BDN and RDM, spreading to all other sites by daybreak Tuesday. Evans/74 && PREV DISCUSSION... /issued 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 && .PRELIMINARY POINT TEMPS/POPS... PDT 98 64 100 67 / 0 0 0 20 ALW 97 68 99 70 / 0 0 0 10 PSC 99 64 102 66 / 0 0 0 10 YKM 97 65 100 65 / 0 0 0 0 HRI 99 64 102 68 / 0 0 0 10 ELN 95 63 96 65 / 0 0 0 0 RDM 95 60 94 54 / 0 20 10 20 LGD 94 59 96 64 / 0 0 0 20 GCD 97 61 96 61 / 0 10 10 30 DLS 101 68 96 66 / 0 0 0 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Heat Advisory until 9 PM PDT Tuesday for ORZ041-044-507-508-510. WA...Heat Advisory until 9 PM PDT Tuesday for WAZ024-026>029-521. && $$ SHORT TERM...86 LONG TERM....86 AVIATION...74