Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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153 FXUS66 KPDT 251748 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1048 AM PDT Wed Sep 25 2024 .Updated for Aviation... .AVIATION... 18Z TAFS...A strong cold front will move across the area from west to east this afternoon into early evening. Winds will increase and become quite gusty along and ahead of the front with gusts generally in the 25 to 30 kt range. By early early evening winds should begin to subside to around 10 kts and become less than 10 kts by Thursday morning. With the gusty winds, it is possibly for some BLDU, especially in the Columbia Basin, which would most likely impact DLS and PSC, but could affect anywhere. If BLDU does occur, it would bring reduced VSBYS to MVFR, and possibly lower. The timing and extent is difficult to pinpoint. For now, have added some reduced VSBYS at PSC and excluded it elsewhere. && .PREV DISCUSSION... /issued 432 AM PDT Wed Sep 25 2024/ PREV DISCUSSION... /issued 259 AM PDT Wed Sep 25 2024/ SHORT TERM...Today through Friday night...Wind advisories and blowing dust advisories are in effect this afternoon and evening across portions of south central WA and north central OR. A mostly dry cold front accompanied by a strong low level jet will sweep across the region this afternoon and evening. The front has stalled along the eastern Pacific this morning due to a shortwave circulation riding north along the leading edge of the front off the northern CA coast, as evident by water vapor loops. Due to its slower timing, the gusty winds will not materialize until mid afternoon. Therefore, the start time of the advisories will be postponed to 2 PM rather than 11 AM. ECMWF EFI continues to place a large portion of the forecast area in the 0.7-0.9 for wind gusts meaning winds will be stronger than seasonal climatology. There are signs of isentropic descent bringing 35-40 kts of 850mb towards the surface. Blowing dust is common in late September across the Columbia Basin, so confidence that patchy blowing dust will be observed is high (80%) and confidence in areas of blowing dust is moderate to high (50-60%). The hot dry windy product has consistently indicated unusually dry and windy conditions today for eastern WA/OR. Although the RHs will not be critically low where the strongest winds occur, the expected dry and breezy weather is something to highlight in the fire weather forecast and social media. Models have trended drier with the front, so the QPF amounts today will be light. PoPs will show 40-60% over the mountains, primarily due to orographic lift and just a few hours of scattered showers. The Columbia Basin down to central OR may see little to no measurable rainfall with the passing front. Will keep the isolated thunderstorms over the eastern mountains with the best chance over the Blue Mountains north of Meacham. There are modest CAPEs approaching 500 J/kg and 60-70 kts of 0-6km shear, so storms will be organized and capable of brief heavy downpours, hail and strong outflows. NBM continued to shows 20% chance of thunderstorms along the WA Cascades and will keep, although CAMS have little indications of storms in that area. Near seasonal temperatures, partly to mostly cloudy skies, and locally breezy winds can be expected Thursday through Friday night. There is a 30-60% chance of showers along the east slopes of the WA Cascades Thursday night, associated with a Pacific front over western WA that falls apart Friday morning with the advection of mid level dry air. Wister/85 LONG TERM...Saturday through Wednesday...A shortwave trough moves inland of the PacNW through the weekend, bringing southwest flow but no significant weather. Winds will remain fairly light with occasional breezes up to 20 mph due to increased westerly flow (>70% probability). An upper ridge will then build over to the PacNW Monday with remained fairly light winds and lingering breezes (>70% probability). Models deviate for Monday where the ECMWF and Canadian model both favor the ridge building over, but with GFS appearing more zonal. Tuesday through Wednesday, the ridge will break down as another shortwave trough occurs with a cold front inland of the forecast area. With orographic lifting and southwest flow, slight chances (15- 20%) of showers could increase at the west of Kittitas Valley. Overall, models are in good agreement with the southwest flow over the forecast area. High temperatures will remain mainly in the 70s through the long term period. Feaster/97 && .PRELIMINARY POINT TEMPS/POPS... PDT 83 47 73 49 / 20 50 0 0 ALW 87 51 75 53 / 30 60 0 0 PSC 87 52 76 56 / 20 30 0 0 YKM 82 40 73 46 / 30 10 0 10 HRI 85 50 76 53 / 20 30 0 0 ELN 79 43 73 49 / 40 20 0 20 RDM 82 45 78 44 / 10 20 0 0 LGD 87 48 76 48 / 10 60 0 0 GCD 87 48 80 48 / 10 30 0 0 DLS 79 48 77 54 / 40 30 0 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Wind Advisory from 2 PM this afternoon to 11 PM PDT this evening for ORZ041-507-508-510. Blowing Dust Advisory from 2 PM this afternoon to 11 PM PDT this evening for ORZ044. WA...Wind Advisory from 2 PM this afternoon to 11 PM PDT this evening for WAZ024-026-027-029-521. Blowing Dust Advisory from 2 PM this afternoon to 11 PM PDT this evening for WAZ028. && $$ SHORT TERM...85 LONG TERM....97 AVIATION...77