Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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621 FXUS66 KPDT 292322 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 422 PM PDT Sat Jun 29 2024 .Updated for Aviation... .PREV DISCUSSION... /issued 153 PM PDT Sat Jun 29 2024/ SHORT TERM...Today through Monday...SW flow aloft is currently enveloping the forecast area as a broad trough moves into the PacNW. Much of the region has been enveloped with cloud cover as a result, which is expected to continue until drier air filters in from behind the trough passage by early Sunday. Until then, light mountain showers are possible, primarily for the Washington Cascades and eastern mountains. Thunderstorms had previously been a concern, but given the ongoing cloud cover across the area, current thinking is that any thunderstorm activity that develops today will be very isolated and short-lived in nature. Latest CAMs suggest that shower activity will dwindle overnight, with perhaps a few lingering showers over Wallowa County by daybreak Sunday, but largely ending by late afternoon Sunday at the latest. The trough passage will bring in breezy winds Sunday into Monday, however gusts are expected to be relatively moderate - roughly 30 to 35 mph across our more wind prone areas with widespread 20 to 30 mph gusts elsewhere. Could see isolated 40+ mph gusts, mainly on Monday, for the Kittitas Valley and Columbia River Gorge, but winds look to overall fall short of advisory criteria. Given the marine push brought about by the trough passage, RHs look to remain above critical levels as well, so even though breezy conditions will exacerbate fire spread concerns, critical fire weather conditions are overall not anticipated. Temps will be relatively stagnant through the short term, with highs in the 80s and 70s in the mountains, before a more distinct warming trend takes place later on in the upcoming work week. Evans/74 LONG TERM...Tuesday through Saturday...Deterministic models and ensembles are in good agreement on the 500 mb pattern through much of the period, though there is some uncertainty in how hot it will get mainly on Saturday. The upper pattern starts out with a NW flow aloft on Tuesday with an upper ridge offshore and a trough over SW Canada. A shortwave will move through the flow across NRN WA and NRN ID Tuesday night and Wednesday. This will result in breezy winds in the Cascade gaps both Tuesday and Wednesday afternoon and evening, but strongest on Tuesday. As of right now the need for wind highlights looks low (20-30%) with most wind gusts in the 30-40 mph range mainly Tuesday. On Tuesday and Wednesday high temperatures will be within 2-3 degrees of normal. However on Thursday as the ridge begins to build northward and closer to the coast, high temperatures will warm into the low to mid 90s in the lower elevations. The ensemble clusters do show some variability for Friday and Saturday but there is roughly an 80% chance of an upper ridge being located over the area or just offshore. However there is a low probability (roughly 10% chance of occurring) alternate scenario worth mentioning where the ridge breaks down and temperatures cool to near normal. The warmer scenario from the NBM was used for this forecast. For Friday and Saturday it looks to be hot with high temperatures in the mid 90s to around 100 in the lower elevations Friday, and upper 90s to low 100s on Saturday. Of note, the raw 850 mb temperatures from the GFS support even warmer high temperatures on Saturday. With the building heat toward the end of the week the experimental HeatRisk product is highlighting concerns for sensitive groups Friday and even more so for Saturday. This situation will have to be monitored as next week progresses. With almost no chance of rain (less than 5% chance) and decreasing afternoon humidities with time (as low as 10-15% Friday and Saturday), fire weather concerns will be elevated. However winds will be decreasing with time as the upper ridge builds over the area, which will help to mitigate the overall threat somewhat. 78 AVIATION... 00Z TAFS...VFR conditions are expected through the TAF period. A weak system passing over the region will keep clouds over most of the area. Much of the guidance brings SHRA east of the TAF sites later tonight (after 30/06Z) however some of the shorter range guidance brings at least a chance to PDt and ALW. So have included a TEMPO group at these locations though confidence is no higher than 40 to 50%. Wind gusts at DLS, BDN and RDM will decrease in the 30/04-05Z range and every site should be 10 kts or less afterward. All locations will have gusty winds again on Sunday with wind gusts generally 20-25 kts and increasing from the morning through the afternoon hours depending on location. && .PRELIMINARY POINT TEMPS/POPS... PDT 59 82 54 81 / 20 0 0 0 ALW 63 86 57 85 / 30 10 0 0 PSC 63 88 59 89 / 10 0 0 0 YKM 56 84 54 85 / 20 0 0 0 HRI 62 87 58 87 / 20 0 0 0 ELN 57 75 54 78 / 30 0 0 0 RDM 49 78 47 79 / 10 0 0 0 LGD 56 78 50 77 / 40 20 0 0 GCD 54 81 49 80 / 40 10 0 0 DLS 61 81 59 81 / 10 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...74 LONG TERM....78 AVIATION...77