Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
758 FXUS66 KPDT 290518 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1018 PM PDT Sat Jun 28 2025 .Updated Aviation Discussion. .AVIATION...06Z TAFS...VFR conditions currently across all sites, which will stay the course through the period. Skies will stay clear with light winds below 10 kts. 75 && PREV DISCUSSION... /issued 202 PM PDT Sat Jun 28 2025/ SHORT TERM...Today through Monday night...Quiet weather is forecast for the remainder of today and Sunday as an upper-level ridge of high pressure builds into the Pacific Northwest. Breezy winds through the Cascade gaps this afternoon and evening will diminish overnight with a reversal to a lighter offshore flow anticipated Sunday into Monday. Ensemble NWP is very confident (95% or greater) that the aforementioned upper-level ridge will amplify through Monday, and an upper-level closed low will develop off the central California coast Sunday through Monday, setting the stage for area-wide heat and convection in southern/eastern Oregon for 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 due to weak forcing aloft. That said, have introduced a slight chance (15%) of thunderstorms in the forecast for the east slopes of the Oregon Cascades roughly from Santiam Pass south, and across the Ochocos and John Day Highlands. 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 90-103 degrees and overnight low temperatures of 59-73 degrees. Will note there is some uncertainty in high and low temperatures Tuesday, (and especially Wednesday in the "LONG TERM") due to potential cloud cover -- convective debris or otherwise. Plunkett/86 LONG TERM...Tuesday through Friday...Confidence is high that an upper-level ridge of high pressure will be overhead Tuesday. Above-normal temperatures are expected region-wide, and mostly dry conditions are anticipated outside of 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. 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 Friday. 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 54 91 59 99 / 0 0 0 0 ALW 59 91 63 97 / 0 0 0 0 PSC 58 92 61 100 / 0 0 0 0 YKM 57 90 61 98 / 0 0 0 0 HRI 57 92 59 101 / 0 0 0 0 ELN 53 89 58 97 / 0 0 0 0 RDM 46 89 52 96 / 0 0 0 0 LGD 51 87 55 94 / 0 0 0 0 GCD 50 90 57 98 / 0 0 0 0 DLS 60 94 64 99 / 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...75