Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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554 FXUS66 KPDT 032323 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 425 PM PDT Wed Jul 3 2024 Updated Aviation Discussion .SHORT TERM...Tonight through Friday night...Water vapor imagery reveals an amplifying upper-level ridge offshore in the Pacific, a harbinger of the much-advertised upcoming heat wave. Ensemble guidance is in excellent agreement (100% chance) that the aforementioned ridge will continue to amplify through the week, slowly migrating eastward such that mid-level height rises are anticipated each day over the forecast area. This will support a warming trend of 5-10 degrees each day through Friday, culminating in widespread afternoon high temperatures in the 90s to lower 100s by Friday afternoon. NBM probabilities suggest the chance of exceeding 100 degrees is broadly 20-50% across the lower elevations, except locally 60-90% in the hottest areas of the eastern Columbia River Gorge as well as central and north-central OR. In tandem with modest overnight temperature recovery (lows in the mid-50s to upper 60s), this will facilitate Moderate to Major HeatRisk across the lower elevations. After coordination, we have opted to issue a Heat Advisory for the Lower Slopes of the Eastern Washington Cascades Crest, valid noon Friday until 10PM PDT Tuesday. This zone joins our non- mountain zones (except the Grande Ronde Valley) where existing heat highlights (Advisory or Warning) are in effect for the same period. While mountain zones will certainly observe above-normal temperatures, forecast lows in the 50s preclude HeatRisk values above Moderate at this time and do not support Heat Advisories. Should confidence in warmer overnight lows develop, additional highlights may be needed for these areas. In terms of fire weather concerns, the combination of a dry air mass and hot temperatures will induce very low afternoon RHs in the single digits and teens. However, surface pressure gradients are not anticipated to be supportive of more than locally breezy winds each afternoon and evening through the Cascade gaps and across central OR. Thus, Red Flag conditions are not forecast at this time. While heat highlights start Friday afternoon, the bulk of the heat wave will commence Saturday. More details are given in the discussion below. Plunkett/86 && .LONG TERM...Saturday through Wednesday...There is very good model agreement with the building of a strong and persistent upper ridge over the west through the extended (and likely beyond). The center of the ridge will actually slide southeast through Monday, and remain over California, then reposition itself and strengthen further for the early and middle part of next week. What this means is that very hot temperatures will linger into next week, with virtually no chance of any precipitation. Excessive heat warnings and heat advisories have been issued through Tuesday at this time and will monitor for any possible extensions. HeatRisk values will generally be Moderate to Major, with some locations even reaching the Extreme category. Anyone who is outside for long period of time, and especially those who are heat sensitive should take precautions during this extended heat wave, including adequate hydration and trying to spend some time indoors. Highs across the lower elevations will generally be 100 to 105 degrees (90-100%) in most areas with 105 to 110 degrees in the Columbia Basin (90-100%). These temperatures would be about 20 degrees above normal. Some records temperatures are also expected. ECMWF EFI values for high temperatures range from 0.6 to 0.9 across the region (generally from west to east) and increasing though early next week. The ensembles are in generally good agreement as well and supportive of the strong ridge solution (>60%) beyond midweek. The GFS ensembles have at least several members >=110 degrees in the Columbia Basin Monday through Wednesday. The ECMWF has many members. The ECMWF may be overdone while the GFS is underdone, but guidance does indicate at least some potential for high temperatures >=110 degrees in the Columbia Basin, especially early next week. At this point the most likely days would be Monday- Wednesday (with 50% at best at this time). && .AVIATION...00Z TAFS...Clear skies and light terrain driven winds will continue througn 00Z/5th. Wister/85 && .PRELIMINARY POINT TEMPS/POPS... PDT 54 90 58 95 / 0 0 0 0 ALW 57 93 60 98 / 0 0 0 0 PSC 58 94 62 100 / 0 0 0 0 YKM 54 93 59 99 / 0 0 0 0 HRI 56 95 59 100 / 0 0 0 0 ELN 56 93 59 99 / 0 0 0 0 RDM 48 92 54 98 / 0 0 0 0 LGD 51 87 55 91 / 0 0 0 0 GCD 50 91 55 95 / 0 0 0 0 DLS 59 97 64 104 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Excessive Heat Warning from noon Friday to 10 PM PDT Tuesday for ORZ041-044-507-508-510. Heat Advisory from noon Friday to 10 PM PDT Tuesday for ORZ505- 511. WA...Excessive Heat Warning from noon Friday to 10 PM PDT Tuesday for WAZ024-026>029-521. Heat Advisory from noon Friday to 10 PM PDT Tuesday for WAZ523. && $$ SHORT TERM...86 LONG TERM....77 AVIATION...85