484 FXUS66 KPDT 181128 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 328 AM PST Tue Nov 18 2025 Updated Aviation Discussion .AVIATION...12z TAFs...Low, MVFR cigs will linger around several sites (namely PDT, PSC, RDM, and BDN) early this morning, before some clearing is expected heading into the afternoon. A deck of bkn-ovc cigs around 15 kft will then move in, before much of the area sees clearing once again late Tuesday evening. Low cigs and even fog may return toward the very tail end of the period, given the light winds and relatively clear skies expected in the evening prior. Otherwise, for the afternoon hours, VFR conditions are anticipated. 74 && .PREV DISCUSSION... /issued 306 AM PST Tue Nov 18 2025/ DISCUSSION...Today through Wednesday: A shortwave trough to the north continues to drag a cold front boundary across the far eastern WA tonight, with light showers now diminishing in the lower Columbia Basin. Breezy winds have developed with the frontal passage, with breezy winds along the Blue mountain foothills and portions of the Columbia Basin expected to continue through sunrise this morning. Otherwise, plenty of clearing has occurred behind the frontal passage, with the back end of the associated stratus layer entering eastern portions of the Basin. The next in a series of shortwaves will pass over the PacNW today, however a lack of moisture with this system will only result in light precip along the WA Cascade crest and interior northern Blues through this afternoon, with precip consisting of snow or a rain/snow mix near pass levels. A colder and drier airmass will filter into areas east of the Cascade crest tonight, and coupled with clearing skies, lower elevation locations and mountain valleys will be looking at morning low temperatures below freezing Wednesday. There is moderate-high confidence (65-85%) that areas of the eastern Columbia River Gorge will see their first freeze of the fall/winter, which has resulted in a season ending freeze warning for Wednesday morning. In tandem with the clearing skies and lower temperatures, more moist conditions near the surface may also result in areas of patchy dense fog/freezing fog developing across the lower elevation and mountain valleys (confidence 40-65%) Wednesday morning, though confidence is low (15-25%) in the details for where and when fog may develop. Wednesday, a transient upper ridge will slide over the PacNW, resulting in dry, cool conditions with light winds. Thursday through Saturday: A semi-active weather pattern, though with light precipitation, will continue through the latter half of the work week into the weekend. Ensemble GFS and ECMWF guidance are in agreement of an upper trough approaching the PacNW Wednesday night, then transitioning into a closed low that will dive south along the coast and into CA Thursday. The closed low will clip the western and southern portions of the forecast area, resulting in light rain and mountain snow across the Cascade crest as well as across portions of central OR and the Blues (confidence 50-70%). Dry conditions will briefly develop Thursday night as the low moves further south of the region, but light rain with light snow mainly above 5kft to 6kft will redevelop along the Cascade crest and northern Blues Friday through the weekend as zonal flow develops aloft (confidence 50-75%). Sunday through Monday:Ensemble cluster guidance shows good agreement that the zonal flow aloft will persist through Sunday afternoon, with a southerly component developing as a trough dives down the BC coast. Sunday night through Monday, ensemble guidance comes into disagreement in timing and strength of the trough passage. One solution (GFS member majority) has the trough axis overhead by Monday afternoon, while another solution (ECMWF member majority) has the trough axis still offshore. The latter solution would delay more widespread precip while the former would result in widespread precip chances by early Monday morning. What these solutions do agree upon is that snow chances would be limited to the mountain zones. That said, there is yet another solution (made up of ECMWF and GFS members) that would arrive with a much colder airmass and widespread light snow or rain/snow mix to the lower elevations Monday. While confidence is moderate (40-65%) in widespread precipitation chances across the forecast area Sunday night into Monday, confidence is low (10-20%) precipitation type and amounts. Lawhorn/82 && .PRELIMINARY POINT TEMPS/POPS... PDT 50 30 48 31 / 0 0 0 10 ALW 49 34 48 34 / 10 10 0 10 PSC 52 29 49 31 / 0 0 0 10 YKM 50 29 49 31 / 0 0 0 10 HRI 51 30 48 31 / 0 0 0 10 ELN 47 27 46 29 / 10 10 0 20 RDM 48 21 51 26 / 0 0 0 20 LGD 50 29 51 33 / 10 10 0 10 GCD 50 31 54 34 / 0 10 0 20 DLS 52 34 50 37 / 0 0 0 30 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Freeze Warning from 11 PM this evening to 10 AM PST Wednesday for ORZ041. WA...Freeze Warning from 11 PM this evening to 10 AM PST Wednesday for WAZ024. && $$ DISCUSSION....82 AVIATION...74