Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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658 FXUS66 KPDT 230530 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1030 PM PDT Sun Sep 22 2024 Updated Aviation Discussion .SHORT TERM...Today through Tuesday... Bottom Line Up Front 1. Breezy conditions through Cascade Gaps today 2. Dry and warming conditions through mid-week Models show the flattened ridge to be steadily creeping overhead while an upper level shortwave makes its way across the area. Current observations show the shortwave to be just west of the Cascades over the Olympic Peninsula making its way eastward. As the shortwave traverses over the Cascades a bit later today, models show an increase in the surface pressure gradients at the surface, especially between Seattle and Ellensburg. Roughly 4 mb increasing to 7 mb during the passage will increase winds through the Kittitas Valley as well as the Gorge with the energy of the wave focused closer to the Kittitas Valley. 80-100% of the raw ensembles show the Kittitas Valley will see sustained winds of 20 mph or greater with gusts gusts to 30 mph beginning around 3 PM and lasting through the overnight period and shifting slightly eastwards from Ellensburg. The Gorge however, only show 40-60% of the raw ensembles seeing 20 mph sustained winds with less than 15% showing gusts to 30 mph and tapering off around 10 PM. With that said, the Kittitas Valley will continue seeing breezy conditions through the period as the ridge remains more zonal bringing continued westerly flow aloft keeping the winds elevated near 20 mph with 60-80% of the ensembles in agreement. After today, the most exciting thing is...well...nothing in the short term. Benign weather will persist through Tuesday as the ridge settles in overhead. Models show the ridge to be flat with the majority of the amplitude directed over central OR. Temperatures are steadily increasing as the ridge remains in place with the warmest temperatures settling over central OR Tuesday. Over 60% of the raw ensembles have the majority of the low elevations and central OR in the low 80s, 70s along the mid elevations and 60s along the higher. Mondays temperatures creep up a few degrees and then settle into the warmest temperatures on Tuesday. EFI shows Tuesday to also be above seasonal average with temperatures pushing into the 90s through central OR with 70% of the raw ensembles in agreement. As for the lower elevations 60% of the ensembles show the PDT area in the low mid to upper 80s and 80% show the same temperature as PDT in the Basin. Mid level and higher terrains will see low to mid 70s. Not so fall after all this week...yet. Bennese/90 .LONG TERM...Wednesday through Sunday...A fairly strong cold front has been progged by the models for at least several days now, so confidence is high that this front will have some impacts on the weather. Main impact will be winds. The ETA of the front will be late in the afternoon to early evening, and winds aloft will increase and pressure gradients will tighten with the cold frontal passage. Ensemble means show 25-30 kts at 850 mb and 40-45 kts at 700mb over the Lower Columbia Basin. The ECMWF EFI places central Oregon in the higher category of above average wind gusts with a 0.85 out of 1.0. I am not anticipating a high wind event, but there may be a need for wind advisories in some zones. There is deep dry air behind the front, but the dry air intrusion will occur as winds decrease. The afternoon RHs will be in the 20s to lower 30s--not critical for red flag conditions (confidence 60%). Most precipitation on Wednesday will be west of the Cascades, but there will be enough orographic lift for showers east of the Cascade crest and the northern Blue Mtns. There will be a cooling trend behind the front starting Thursday. Models are in agreement of a straight zonal flow through Friday for dry and seasonal weather. However, model differences begin to show for the weekend forecast. There is a shortwave advertised by the models north of the CWA, but there are timing differences as well as minor differences in the amplitude of the trough. Some show the trough passage along the BC/WA border on Saturday (mainly the ECMWF ensembles) while others have a little more amplitude and slower timing (mainly the Canadian) and track it across WA state. Current forecast will keep mostly dry conditions this weekend, but a slight chance of showers may need to be introduced if models come into better agreement with the timing and strength of the trough. Wister/85 .AVIATION...06Z TAFs...VFR conditions to prevail through the period. High level clouds sct-bkn 15kft-25kft will continue to impact sites through the period. Winds will be light, less than 12kts, through the period at all sites. Lawhorn/82 && .PRELIMINARY POINT TEMPS/POPS... PDT 51 79 53 87 / 0 0 0 0 ALW 55 82 56 89 / 0 0 0 0 PSC 56 83 56 87 / 0 0 0 0 YKM 52 84 53 87 / 10 10 0 0 HRI 55 83 55 89 / 0 0 0 0 ELN 56 82 54 87 / 10 10 0 0 RDM 46 80 48 90 / 0 0 0 0 LGD 48 78 49 86 / 0 0 0 0 GCD 46 78 50 87 / 0 0 0 0 DLS 59 86 59 92 / 10 10 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...90 LONG TERM....85 AVIATION...82