266 FXUS66 KPDT 132144 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 244 PM PDT Mon May 13 2024 .SHORT TERM...Today through Wednesday Night... Key Messages: 1. Windy conditions across the Kittitas Valley through Tonight. 2. Elevated river levels on the Naches River. An upper level shortwave will continue to pass through the area this evening, which will allow a slight increase in cloud cover and a pressure gradient to develop along the Cascades to promote elevated winds over the Kittitas Valley, Simcoe Highlands, Eastern Gorge, and the northern Blue Mountain foothills. Maximum wind gusts of 44 mph have already been observed at the Ellensburg Airport, with the pressure gradient and winds expected to peak between 5 PM and 11 PM this evening. This has warranted the issuance of a Wind Advisory for the Kittitas Valley through 11 PM as gusts of up to 50 mph will be possible. The 44 mph gusts occurred during an observed pressure gradient of 8.7 mb between Portland and Spokane, and the pressure gradient is expected to top out just shy of 11 mb via GFS guidance. Confidence in wind gusts reaching 50 mph is moderate to high (70-80%), as the NBM suggests a 75% chance at Ellensburg, increasing to an 86% chance of gusts reaching 47 mph or greater. The consistent above normal temperatures coupled with the mountain snow event preceding the warm temperatures last weekend have allowed for some elevated river levels - primarily for the Naches River. The currently level of the Naches River at Cliffdell is 28.86 feet, as action stage is forecast to be reached Tuesday evening and peak Friday morning at 29.76 feet. Confidence is high (>95%) in this reach breaking into action stage, but low (<5%) in reaching minor flood stage (31 feet). The Naches River at Naches is currently at 15.38 feet, and is also expected to reach action stage (16 feet) Thursday morning. This reach is forecast to peak Friday morning at a level of 16.3 feet before dropping below action stage Saturday morning. Confidence in reaching action stage is moderate (62%), as reaching minor flood stage is low (<5%). All other area rivers are currently forecast to stay well below action stage. An upper level ridge will build offshore as high pressure infiltrates into the region from the west. This will keep skies mostly sunny and conditions dry. Northwest flow aloft will set up in the wake of the passing shortwave tonight into Tuesday, dropping high temperatures slightly by 1-3 degrees from today. Flow will incur more of a westerly component to keep temperatures above normal and increasing high temperatures 5 to 9 degrees Tuesday to Wednesday. Afternoon humidities will be on the decline, dropping about 5% Monday to Tuesday and another 3% to 6% on Wednesday. 75 .LONG TERM...Thursday through Monday...Dry, northwesterly flow continues through Thursday afternoon as high pressure remains anchored off the Pacific Coast. A shortwave will begin to move through the northern reaches of the forecast area Thursday night, producing a slight chance (10-20%) for showers over the Washington Cascades. The shortwave will dig further south through Friday, bringing cooler air with it, though leaving showers generally confined to the Washington Cascades. Temperatures across the area will cool 10 to 15 degrees under the influence of this shortwave, though values still generally remain 5 degrees above seasonal averages. The other impact related to this system will be an increase of gusty to breezy wind both late Thursday and again Friday afternoon. The strongest winds are expected across the Columbia Basin and into the Yakima and Kittitas Valleys where wind gusts of around 35 kts are highly favored (75- 95%). Beyond Friday, model disagreements become more apparent, with the clusters showing variations in both placement of the next area of low pressure, as well as the intensity of it. Current forecast indicates a slightly stronger lean towards a solution with moisture across the Pacific Northwest, though mostly west of the Cascades. The Oregon and Washington Cascades present in this forecast area will see a slight chance (15-30%) for mountain showers into early next week. A slightly better agreement is demonstrated for Monday as low pressure is favored to impact the Pacific Northwest. Cooler temperatures will return, along with a larger coverage area for shower activity. In addition to the Oregon and Washington Cascades, guidance demonstrates the potential (10-20%) for showers to develop across the Blue Mountains on Monday. This system will again create increased winds across the region, with a 50-70% chance for gusts of 30 to 35 kts. Branham/76 && .AVIATION...18z TAFs...Widespread VFR with dry conditions through the TAF period. Gusty winds will be remain this afternoon. Guidance indicates a high chance (70-100%) for gusts of at least 22 kts for today across most terminals. The focus for the strongest wind lies between KDLS and KYKM where a high chance (75-95%) for gusts of 34 kts today. Winds are anticipated to lessen through the later portion of the forecast period, especially after around 10z Tuesday. Branham/76 && .PRELIMINARY POINT TEMPS/POPS... PDT 46 74 47 80 / 0 0 0 0 ALW 50 76 52 82 / 0 0 0 0 PSC 53 81 54 87 / 10 0 0 0 YKM 46 81 49 87 / 0 0 0 0 HRI 50 80 50 86 / 0 0 0 0 ELN 46 75 49 82 / 0 0 0 0 RDM 41 73 43 80 / 0 0 0 0 LGD 44 72 44 77 / 0 0 0 0 GCD 42 73 44 79 / 0 0 0 0 DLS 50 80 53 85 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...Wind Advisory until 11 PM PDT this evening for WAZ026. && $$ SHORT TERM...75 LONG TERM....76 AVIATION...76 |