Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
363 FXUS66 KPDT 092217 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 217 PM PST Sat Nov 9 2024 .SHORT TERM...Tonight through Monday...The remnants of a weakening upper level trough is passing over the region late today and overnight. This will produce some light precipitation across the forecast area overnight through Sunday morning before it exits to the east leaving just some lingering mountain showers. Precipitation amounts will range from a couple hundreths in the lower elevations to .10-.20 inches in the mountains. There is not much cold air with this so snow levels remain high at around 6000 to 7000 feet with very little accumulations. A deeper and stronger upper level trough over the Gulf of Alaska will be approaching the Pacific Northwest late Sunday. This will clip the forecast area with a warm front Sunday night followed by a cold frontal passage on Monday. The brunt of the warm frontal precipitation will be along the Cascades and the east slopes of the Washington Cascades Sunday night with snow levels remaining around 6000 feet. The warm front will bring increasing warm southerly winds across eastern Oregon overnight but not have much impact in the lower elevations around the Columbia Basin. The cold front then passes over the forecast area on Monday shifting the winds to westerly and begins to ushers in cooler air and lowering snow levels through the day and overnight. The combination of a warm front followed by cold frontal precipitation will bring a high probability (60-90%) of around 1 inch to the Cascade crest but without cold air support there will not be much snow accumulation through Monday afternoon. Lowering snow levels Monday night into Tuesday to 3500 to 4500 feet will produce some snow along the crest at the magnitude of 3 to 6 inches above 4000 feet. Snow levels will lower over the eastern mountains Monday night resulting in 1 to 3 inches above 4000 feet. .LONG TERM...Tuesday through Saturday... Key Messages: 1. Progressive rounds of precip and gusty winds through Thursday morning. 2. Snow levels drop Thursday onwards. 3. Cooler temps occur Friday into Saturday. This long term period is characterized by progressive frontal systems sweeping across the PacNW, bringing rounds of precip and gusty winds. Potential mix of mountain rain and snow might also be produced due to excessive moisture from these systems. Over 50% of the raw ensembles favor QPF amounts exceeding between 0.50-1" along the WA/OR Cascades through Thursday before steadily decreasing Friday until the next system occurs Saturday night. The northern Blues has a 40-80% probability of QPF amounts at 0.25-0.50". The remaining mountain areas (rest of the Blues and high terrains of central OR) will have a bit lighter QPF at around 0.10-0.15" (>50% prob) through Friday as the trough begins moving out of the area. Things should gradually simmer down a bit Friday as the shortwave trough moves eastward before we enter in between systems Saturday. However, lingering mountain showers will be left behind from Tuesday`s and Wednesday`s frontal systems. And given the increased west to southwesterly flow from this weather pattern, there is a moderate to high chance (50-90%) of gusty winds (25-35 mph) over the Foothills, Grande Ronde valley, the Simcoe Highlands, the Gorge and Santiam Pass Tuesday into Thursday morning. Though, breezy winds (up to 25 mph) returns across the forecast area Thursday afternoon onwards as the frontal system weakens. Snow levels for Tuesday will be 4-4.5 kft with the cold front moving across our area, then increases above 5kft Wednesday into Thursday morning as the warm front passes. Snowfall may accumulate up to 4-8" at the crest of the Cascades including Santiam Pass through Wednesday (>60% prob). Snow levels will then steadily drop with another frontal system arriving Thursday night into Friday from 4- 4.5 kft to 3-4 kft with >40% prob for snowfall developing up to 6" over those areas. Snow levels for Saturday drops further to 2-3 kft as the trough exits the PacNW with lingering showers for snowfall to exceed up to 3-4" over the Cascades including Santiam Pass (30-60% prob). Temperatures will be seasonably warm for Tuesday through Thursday due to the warm front. However, temps will then start steadily becoming cooler Friday onwards with the trough sweeping across the PacNW. Feaster/97 && .AVIATION...00Z TAFs...VFR conditions continues prevailing for rest of the TAF period with KDLS currently having light showers. Light rain develops tonight with the frontal system passing through. MVFR conditions may occur at KPDT and KALW tomorrow morning due to CIGs and VSBYs dropping from the fog/mist and low clouds. However, VSBY for KPDT will improve tomorrow afternoon. No IFR concerns for now but will monitor and make adjustments when necessary. Winds remains less than 10 kts. Feaster/97 && .PRELIMINARY POINT TEMPS/POPS... PDT 40 55 46 56 / 60 30 30 90 ALW 41 56 47 57 / 70 40 40 90 PSC 42 55 47 59 / 60 10 50 80 YKM 36 53 41 56 / 60 10 80 80 HRI 41 56 45 58 / 60 20 40 80 ELN 35 51 40 52 / 60 10 90 90 RDM 39 58 43 50 / 60 10 30 90 LGD 39 50 43 49 / 70 60 20 100 GCD 39 53 42 49 / 50 60 20 100 DLS 42 58 47 58 / 60 10 80 100 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...91 LONG TERM....97 AVIATION...97