FXUS66 KPDT 121127 CCA AFDPDT Area Forecast Discussion...UPDATED AVIATION. National Weather Service Pendleton OR 427 AM PDT Sat Oct 12 2024 .SHORT TERM...Today through Sunday night...This weekend will be quiet and dry due to prevailing upper ridging over the PacNW. For today, the SPC HREF and current satellite trend support mid to high clouds arriving across most of the area with an exception of Kittitas valley and northern portion of the Yakima valley. The clouds will act to limit warming today and assist in keeping the temperatures cool around central OR and the Columbia Basin due to increased cloud coverage. Highs will generally be 2-8 degrees warmer today compared to yesterday. Starting Saturday night through Sunday, the ridge continues with an upper low tracking beneath its flow. Dry conditions will persist throughout the day, nonetheless. Clear skies will then return with few clouds in the area, which warming and ample solar radiation will help promote temperatures to slightly increase. However, clouds will begin arriving again Sunday night associated with a weakening cold front that reaches the Pacific NW. Overall, a slightly warming trend still remains for the highs over the weekend. Confidence increases with EFI showing temps to be at or above seasonal. The raw ensembles even suggested a 60-90% probability of the highs reaching to low to mid 70s or higher at the Columbia Basin, valley zones and some portions of the central OR. That said, temperatures may vary through this weekend depending on the amount of cloud cover we get (50% confidence). Lastly, winds will remain light throughout this weekend. Feaster/97 .LONG TERM...Monday through Friday Night...The long term revolves around a pattern change as mid level ridging over the west gets shunted east by an typical for this time of year eastern North Pacific trough. The main highlights are: - A cold front will start a cooling trend Wednesday with highs a few to several degrees below normal Thursday and Friday after warmer than normal temps Mon-Tue, - A wet and unsettled period Tuesday night through the end of the week with widespread high chances Tuesday night and Wednesday, - Moderate-high chances for peak daily gusts in excess of 35 mph Wednesday across parts of south central WA, Lower Basin, northern OR, and foothills of the Blues, - Potential first snowfall of the season, albeit light, at higher elevations of the eastern mountains and Blues The large scale pattern early Monday will be characterized by an upper-level ridge extending across the west into Nunavut with a embedded upper low in the central Great Basin with a upper-level low in the Gulf of Alaska/eastern North Pacific. This former feature will evolve and dig southeastward with its leading shortwave trough approach the PacNW Tuesday night while shunting east the upper ridge into the central CONUS. Some synoptic differences still apparent in the evolution of this upper-level trough with clustering scenarios increasing ensemble member disagreement with the timing and amplitude. Of which, GEFS and deterministic GFS showing a less amplified and faster lead wave while the EPS and its deterministic showing a more amplified solution. The two outcomes show greater disparity when it comes to precip potential Tuesday Night-Wednesday rather than winds. EPS/ECMWF show a lot stronger IVT with its attendant AR compared to the weaker GEFS and GFS. Of which, areas outside of the WA Lower Basin have high chances (> 70%) for seeing wetting rain of a tenth or more compared to the 50-70% in the Lower Basin. QPF amounts for the mountains over a 24-hr period ending late Wednesday range from a quarter of an inch to 1-2 inches with the crest of the Cascades and upper slopes having the best potential for more than one inch (50-70%) by late Wednesday. That said, considerable increasing spread Wednesday night onward when it comes to additional shortwave troughs coming through and the evolution of the upper trough. Meanwhile, moderate winds are expected early Wednesday with the crossing cold front. 40-70% chances for peak daily gusts in excess of 35 mph Wednesday across parts of south central WA, Lower Basin, northern OR, and foothills of the Blues based on the latest NBM probabilities with modest spread seen in guidance. Increased confidence in breezy/gusty conditions continuing Thursday with winds lessening late Thursday. With the colder air mass and lowering snow levels, there looks to be increasing potential for higher elevations of eastern OR to see their first snow of the season, albeit light amounts. Good agreement with snow level dropping around 4.5-5 kft Wednesday night/Thursday. While much lower precipitation amounts are expected Wednesday night-Thursday, could see higher elevations pick up a dusting or more. This includes US 97 for La Pine South, US 395 Seneca south, and the upper elevations of the Northern Blues in the Umatilla National Forest. && .AVIATION...12Z TAFs...Limited concerns through the TAF period with presently VFR area-wide. Any aviation concerns continue to revolve around smoke layers/smoke transport across central OR, and mainly the KBDN terminal. Of which, continue to see transient impacts with lower ceilings, mainly during the evening and overnight hours. Latest HRRR guidance shows potential for impacts again tonight, however, confidence is low in timing and severity. Otherwise, light winds prevail, generally under 10 kts, with light and variable to calm overnight. && .PRELIMINARY POINT TEMPS/POPS... PDT 67 41 72 43 / 0 0 0 0 ALW 70 45 75 46 / 0 0 0 0 PSC 72 44 74 46 / 0 0 0 0 YKM 72 41 75 42 / 0 0 0 0 HRI 70 43 75 44 / 0 0 0 0 ELN 75 43 76 45 / 0 0 0 0 RDM 70 36 74 39 / 0 0 0 0 LGD 76 42 76 44 / 0 0 0 0 GCD 75 41 76 44 / 10 0 0 0 DLS 75 46 80 49 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...97 LONG TERM....80 AVIATION...80