Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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504 FXUS66 KPDT 131031 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 331 AM PDT Thu Jun 13 2024 .SHORT TERM...Today through Saturday night...Mostly clear skies and a dry air mass have led to efficient radiational cooling for most areas, resulting in cool temperatures nearly area-wide. After the chilly start to the morning, temperatures will increase this afternoon with another warm, dry day anticipated across the forecast area. Winds will be light through afternoon, but a sharp up-ramp in winds is anticipated this evening through the Cascade gaps and into the Columbia Basin as onshore-directed pressure gradients strengthen in response to an approaching trough. Forecast soundings indicate a 30-40kt LLJ over the Columbia River Gorge (CRG) and Kittitas Valley (KV) this evening through Friday morning. Confidence is high (80% chance) that wind-prone locations in the KV will approach or exceed 45 mph wind gusts so have opted to issue a Wind Advisory, valid 8PM this evening until 11AM Friday morning. In the CRG and across the adjoining portions of the Columbia Basin (CB), north-central OR (N-C OR), and the foothills of the Blue Mountains (BMF), confidence is moderate (40-60% chance) in winds reaching advisory criteria so have opted to forgo any highlights. Of note, the nocturnal nature of the event decreases confidence relative to a daytime event. Friday, winds will remain breezy to windy as the first in a series of shortwaves wraps around a deep, upper-level closed low and ejects northeastward into northern WA and southern BC. Due to the trajectory of the impulse, precipitation chances (15-60%) will be confined to the Cascade crest of WA on Friday. Saturday, the second shortwave is advertised to punch across the forecast area, resulting in another round of breezy to windy onshore winds. Winds may approach advisory criteria for wind- prone locations such as the KV, CRG, and portions of the CB and BMF (50-80% chance), but have opted to hold off on any highlights for now. Precipitation chances will increase Saturday, but the best chances (60-90%) will still be pinned to the Cascade crest. Elsewhere, chances are <15% for most of the CB and central OR (C OR), while chances are higher (15-40%) for the BMF and Blue Mountains (BM). Confidence is low (<20% chance) in thunderstorms Saturday afternoon, but steep low- and mid-level lapse rates will lead to modest instability. Plunkett/86 && .LONG TERM...Sunday through Thursday...The forecast starts out on Sunday with some discrepancies on the timing and location of an upper low that will impact the region early next week. The majority of the clusters favor a more offshore solution on Sunday similar to the deterministic GFS compared to the more progressive ECMWF. This will keep shower activity (30-40% chance) confined to the Cascade crest during the day on Sunday. On Monday and Monday night rain showers will spread across the region as the upper low moves across the region...with the potential for wrap around precipitation over the foothills and Blue and Wallowa Mountains on Tuesday. There is a low chance (10-20%)of TSTMS Monday afternoon and evening mainly in Grant County but any storms will remain rather isolated and brief given marginal instability. QPF amounts Monday through Tuesday are forecast to be around .50 inches in the Foothills of the Blues and around 1.00 inch in the eastern mountains with lighter amounts elsewhere. Right now there is a disconnect between the NBM QPF and POPS. Despite the higher QPF amounts the POPS are modest at only 30-50%. Considered bumping POPS up but the ECMWF and GFS ensemble members show considerable spread in QPF amounts with some members showing heavy QPF and others none at all (at KPDT and KMEH for reference). Roughly 10% of the ensemble members are indicating the potential for rainfall exceeding 1.00 inch at KPDT and 2.00 inches at KMEH. Think the QPF and POP inconsistency will decrease with time as the event gets closer. The clusters show considerable spread on how quickly the upper low moves east of the region on Wednesday. Went with the NBM which dries things out on Wednesday but if the low exits the region more slowly, there could be lingering showers over the northeast mountains. There is low-moderate confidence (40-50%) in the forecast for Thursday given the differing cluster solutions. It does appear that the flow will be slightly less amplified which will allow temperatures to warm up. In fact after high temperatures bottom out at 10-15 degrees below normal Sunday and Monday a warming trend will occur through Thursday such that high temperatures will be right about normal Thursday afternoon. 78 && .AVIATION...06Z TAFS...VFR conditions are expected through the period and beyond. Gusty winds at DLS have decreased and winds of 10 kts or less are expected everywhere through the night and much of Thursday. Winds will begin to increase again later Thursday/Thursday evening at DLS/BDN/RDM and winds will gust to around 25 kts at these locations. Everywhere else will be 10 kts or less. && .PRELIMINARY POINT TEMPS/POPS... PDT 83 51 73 48 / 0 0 0 0 ALW 86 55 77 51 / 0 0 0 0 PSC 88 56 80 54 / 0 0 0 0 YKM 85 48 76 46 / 0 0 0 0 HRI 88 55 79 52 / 0 0 0 0 ELN 82 49 71 45 / 0 0 0 0 RDM 82 42 72 41 / 0 0 0 0 LGD 84 49 72 45 / 0 0 0 0 GCD 88 48 75 43 / 0 0 0 0 DLS 84 51 73 51 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...Wind Advisory from 8 PM this evening to 11 AM PDT Friday for WAZ026. && $$ SHORT TERM...86 LONG TERM....78 AVIATION...77