


Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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415 FXUS66 KPDT 162332 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 432 PM PDT Thu Oct 16 2025 Updated Aviation Discussion .AVIATION...00z TAFs...VFR conditions expected. A weather system moving into the region tonight will make for bkn-ovc cigs around 15-20 kft, followed by clearing conditions and an increase in westerly winds Friday afternoon. Any precipitation associated with this system is expected to remain in the mountains. Outside of gusty winds in the DLS this evening, all other sites are expected to see light and terrain-driven winds, before becoming W/NW tomorrow afternoon and gusting up to 25 kts, especially at DLS and PDT. 74 && .PREV DISCUSSION... /issued 250 PM PDT Thu Oct 16 2025/ DISCUSSION...Tonight through Friday, a shortwave passing across the northern Rockies will clip the region, bringing a chance (25-50%) of light rain showers to the Washington Cascade crest with a slight chance (15-20%) farther south over the Oregon Cascade crest; predominantly dry conditions are forecast elsewhere. The main weather concern associated with the system tonight through Friday will be breezy to locally windy west to northwest winds as cross-Cascade pressure gradients strengthen and isentropic descent to the lee of the Cascades facilitates downward momentum transfer to the surface. Additionally, while confidence is only medium (50%), localized Red Flag conditions (overlap of wind/low RH) may develop Friday afternoon through the Kittitas Valley and also limited areas of the east slopes of the Washington Cascade and Columbia Basin. Forecast soundings from some CAMs indicate a layer of very dry air aloft, approximately between 850 and 700 hPa. The main question is if the dry air will be able to mix all the way to the surface. If so, surface dew points in the upper single digits to upper teens would result in significantly lower RH compared to what is shown by NBM guidance. Friday night into Saturday, confidence is very high (>90%) that a temporary ridge of high pressure will move over the Pacific Northwest. The main item to note will be poor to moderate overnight RH recovery for mountain areas, especially the higher mountains. The next chance of widespread precipitation will be associated with a robust low-pressure system that is slated to arrive Saturday into the weekend. A warm frontal passage is anticipated Saturday morning through afternoon, passing from southwest to northeast. Little to no precipitation is forecast with this front. A southwest-to-northeast-orientied cold front will arrive Saturday night through Sunday, sweeping from west to east. Frontal passage is expected to bring breezy to windy conditions to the region, with the best chances (30-70%) of reaching advisory thresholds across our climatologically windy locations -- the Simcoe Highlands, the Blue Mountain foothills, and portions of the Columbia River Gorge and lower Columbia Basin. Snow levels will be high enough to preclude snow at pass level, with the exception of Sunday night into Monday as snow levels lower to 4500-5000 feet behind the cold front. Regarding uncertainty with the weekend system, while ensemble clusters are in excellent agreement (>90% of members) that some form of trough/low will move over the Pacific Northwest through the weekend, they are still unsure on the form (fast-moving trough versus slower-moving closed low) and how much precipitation the region will get. The faster-moving trough solution is becoming more likely (~85% of ensemble members) compared to the slower- moving closed low (~15% of members). The former scenario would lead to less precipitation, especially for the lower elevations, and windier conditions through the Cascade gaps and into the Columbia Basin. Tuesday through Wednesday, not anticipating any significant weather as ensemble NWP suggests a modest chance (35%) of a shortwave traversing otherwise quasi-zonal upper-level flow over the forecast area. && .PRELIMINARY POINT TEMPS/POPS... PDT 41 65 34 64 / 0 0 0 0 ALW 45 64 39 62 / 0 0 0 0 PSC 40 69 34 60 / 0 0 0 0 YKM 40 66 34 59 / 0 0 0 10 HRI 42 67 35 62 / 0 0 0 0 ELN 39 59 30 56 / 0 10 0 10 RDM 34 64 28 70 / 0 0 0 0 LGD 37 63 31 65 / 0 0 0 0 GCD 36 64 32 69 / 0 0 0 0 DLS 47 66 40 63 / 0 10 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...86 LONG TERM....86 AVIATION...74