Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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664 FXUS66 KPDT 210511 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1011 PM PDT Fri Sep 20 2024 .Updated for Aviation... .AVIATION... 06Z TAFS...VFR conditions are generally expected through the period. Smoke or haze from fires in central Oregon could impact BDN/RDM overnight with BDN the more likely location. However, impacts tend to be limited. For now just introduced a SCT layer, and confidence is low (<30%) in MVFR conditions. If any do occur they would likely be brief. Winds will generally be 10 kts or less through the period. && .PREV DISCUSSION... /issued 432 PM PDT Fri Sep 20 2024/ AVIATION...00Z TAFs...VFR conditions forecast through the period for all TAF sites. Smoke/haze from fire activity in central Oregon may drift across BDN/RDM as winds turn southerly, presenting an opaque layer overnight into Saturday morning, but confidence is low (<30% chance) in sub-VFR VSBYs/CIGs. Winds will diminish this evening and overnight, remaining mostly light (<10 kts) Saturday aside from periodic afternoon gusts to 15 kts. Otherwise, some cirrus passing overhead will result in skies ranging from SKC to BKN250. Plunkett/86 PREV DISCUSSION... /issued 219 PM PDT Fri Sep 20 2024/ SHORT TERM...Today through Sunday night... Key Messages: 1. Breezy winds this evening, returning Sunday. 2. Warming trend through weekend, reaching above normal Sunday. Current radar and visible satellite imagery showing dry conditions under clear to mostly clear skies extending across the region. This is in response to an upper level ridge pushing onshore and into the Pacific Northwest in the wake of a weak shortwave along the Canadian border and another slow, upper low pressure system moving east through Southern California. These synoptic features have allowed a weak pressure gradient to develop along the Cascades, providing breezy west northwest winds across the Gorge, Kittitas Valley, and portions of the Basin. Winds of 25-35 mph have been observed at these locations this afternoon, and will begin to dissipate after 9 PM. Confidence in wind gusts of 30 mph or greater is high (80%) over the Kittitas Valley, as the HREF suggests a 70-90% chance of this occurring. The chance of 35 mph wind gusts is considerably lower to between a 10-30% chance. Winds through the Gorge are also expected to be on the lower end of the 25-35 mph range this evening, as the HREF advertises a 30-50% chance of gusts reaching 30 mph or greater, and dropping to a 10% when bumping up gusts to 35 mph. Today`s northwest flow turns more from the west Saturday before a return to northwest flow on Sunday associated with a weak shortwave. This feature on Sunday will attribute to a chance (15-35%) of showers along the Central Washington Cascades and another surface pressure gradient developing along the Cascades. Elevated winds are expected to return to the Kittitas Valley and the Gorge, with gusts of 25-35 mph out of the west northwest and peaking between 2 PM and 6 PM. Confidence in these gusts is moderate (70%) as the NBM suggests a 60-80% chance of gusts of 30 mph or greater over the aforementioned areas Sunday. Elevated winds both today and Sunday are not expected to result in any fire weather concerns, as the afternoon humidities will be improving slightly through the weekend. However, overnight recoveries will be on the decline through Saturday night ahead of excellent recoveries returning Sunday night associated with the incoming shortwave. Temperatures will also be on the increase through Sunday, with above normal high temperatures anticipated and highs breaking into the low 80s for lower elevations of the Basin. Confidence in 80 degree high temperatures on Sunday is moderate (60%) as the NBM showcases a 50-80% chance of Sunday`s highs reaching 80 degrees or above for Yakima (78%), Tri-Cities (51%), and Hermiston (51%). 75 LONG TERM...Monday through Friday... Bottom Line Up Front 1. Dry and warming conditions through mid-week 2. Diurnal winds through the Cascade Gaps 3. Cascade rain and a cooling trend late next week Models are in firm agreement with the upper level ridge moving overhead at the start of the forecast period. Dry and warmer conditions will prevail under the ridge through Wednesday before an upper level trough breaks it down bringing rain to the crests and east slopes of the Cascades as well as diurnally driven enhanced winds across the wind prone areas in the CWA. Even with the upper level ridge moving overhead, EFI is signaling at or near normal seasonal temperatures through Wednesday. Monday the majority of the CWA will see temperatures in the mid to upper 70s with 80-100% of the raw ensembles in agreement. However, 40-60% of the raw ensembles have the Basin and the Gorge in the low 80s. As the ridge settles overhead, temperatures will steadily warm with Wednesday being the warmest day of the period. 70-90% of the raw ensembles show the majority of the lower elevations and central OR to be in the low to mid 80s while the higher mid-level terrains will see upper 70s. Temperature will begin to cool a few degrees as the upper level trough brings with it cooler temperatures bringing the majority of the region back into upper 60s to low 70s. With the current pattern set up under the ridge, winds will remain the typical diurnally driven winds below 15 mph through the Cascade Gaps and along the foothills with 80-100% agreement. However, winds will briefly pick up Wednesday and Thursday as the upper level trough moves across the region. Models do show a very weak pressure gradient moving across the Cascades which will bring the heightened winds. However, only 40-60% of the ensembles show the winds to be at or near 15 mph both days while 60-90% show the region to primarily see winds near 10 mph. Thursday ensembles show much of the same before slightly decreasing Friday. Models are in some agreement with the incoming upper level trough. Clusters show the biggest variance between the models is the timing and precipitation at the onset. EURO brings the trough in much sooner with lighter amounts of precipitation along the Cascades; GFS brings it in faster with much more rainfall associated with it and extending the rain over the Blues. With that said, forecast is using the NBM which appears to be more on track with the EURO solution of light rain along the Cascades and the Blues. 20-40% of the raw ensembles show the WA Cascades seeing 0.02 inches of rain Thursday while less than 20% show 0.01 inches along the Blues. With that said and the fact that this is day 7, confidence in the chances of rain are low (10-20%). Bennese/90 && .PRELIMINARY POINT TEMPS/POPS... PDT 41 72 43 77 / 0 0 0 0 ALW 46 74 47 79 / 0 0 0 0 PSC 47 76 49 80 / 0 0 0 0 YKM 43 75 47 81 / 0 0 0 0 HRI 45 76 46 81 / 0 0 0 0 ELN 42 75 46 80 / 0 0 0 0 RDM 35 71 39 78 / 0 0 0 0 LGD 40 71 41 76 / 0 0 0 0 GCD 37 72 40 77 / 0 0 0 0 DLS 47 79 50 83 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...75 LONG TERM....90 AVIATION...77