textproduct: Pendleton

AVIATION

A breezy/windy and wet forecast in in store for the next 24 hour period of the general area as a prefrontal trough is replaced by a warm front moving across the area on Monday. Some minor impacts to visibility in locally stronger rain rates are possible (4-5sm), however the lower end of the categorical risk is not anticipated as ceilings remain largely above the MVFR level in rain. Strong southwest winds are likely (80-90%) to gust higher than 22 knots and 35 knots is the cutoff, where much lower odds of winds that strong will be at BDN/RDM, but still more likely (65-85% confidence) across terminals like DLS/PSC/ALW/PDT late in the TAF period. Russell/71

PREV DISCUSSION

/issued 239 PM PST Sun Dec 7 2025/

DISCUSSION...Rest of Today: Light rain in the lower elevations has tapered off this afternoon as rain/high elevation snow showers have started to develop along the Cascade crest and portions of the northern Blues. Showers will continue tonight as a quick moving cold front and shortwave slides across the PacNW. Breezy southwest winds will continue overnight behind the cold front passage, but confidence is low (<20%) in wind gusts 45mph or higher developing.

Monday through Thursday: Ensemble and deterministic guidance is in good agreement that multiple surface frontal and upper shortwaves will slide down the west side of an upper ridge of high pressure in the northeast Pacific through the midweek, with each of these systems sliding across the PacNW each day. These systems will also be accompanied by a persistent plume of tropical to subtropical moisture that will see IVT values of 500 to 750 kg/m/s, resulting in high confidence of heavy rain developing across most mountain zones through this period, while a cold front passage Monday night into Tuesday will result in the best chance of moderate to locally heavy rain in the lower elevations (confidence 70-85%). Due to the warmer nature of the incoming AR, snow levels will mainly be above 5.5kft throughout the AR duration, however a cold front passage Monday night into Tuesday will briefly bring snow levels down to pass level in the central WA Cascades with wet snow developing in White, Snoqualmie, and Blewett passes. Otherwise, a low level jet (50-70kts) will move over the PacNW by Monday afternoon, with strong winds mixing down into Columbia Basin/Gorge and adjacent valleys/foothills through Tuesday morning as the cold front moves across the forecast area. Confidence is moderate- high(70-85%) that sustained winds of 25-35mph with gusts 45-55mph will impact wind prone areas, with stronger gusts across exposed ridges in the Columbia Plateau and along the Cascade crest and east slopes.

Over a 3 day period ending Thursday morning (covering the peak of the AR), the NBM shows the WA Cascade crest at a 50-70% chance for at least 7 inches of QPF, while the Cascade crest overall will see a 50-85% chance of receiving 5 inches or more of QPF, and the northern Blue Mountains will see a 35-50% chance of at least 3 inches in the same period. Area rivers and streams will rise beginning early this week as most of the incoming precipitation in the mountains is expected to fall as rain (confidence 65-85%). Of note, rivers originating from the WA Cascade east slopes will see rises into at least action stage Monday night into Tuesday morning (confidence 60-80%), with low confidence (10-25%) in rivers reaching minor flood stages at this time.

By late Thursday, there remains good agreement that the upper ridge offshore will amplify and nudge closer to the PacNW, effectively moving the AR north of the region. Precip chances and amounts will gradually wane from south to north throughout the day, with dry conditions returning to the lower elevations by Thursday night (confidence 55-75%).

Friday into the Weekend: Good agreement remains amongst ensemble guidance that the upper ridge will remain amplified as the ridge axis approaches the PacNW Friday and moves inland Saturday. This will result in precipitation chances mainly across the WA Cascade crest through this period, with dry conditions elsewhere. That said, about 12% of ensemble cluster members (ECMWF, GFS, and Canadian) do favor the ridge being less amplified as it moves inland Saturday, resulting in light rain and high mountain snow across the Cascade crest into Oregon and across the Blue Mountains. Lawhorn/82

AVIATION...00Z TAFS...VFR conditions currently across all sites, but conditions are expected to degrade to MVFR for KDLS toward the end of the period due to reduced visibilities of 4SM and ceilings of 1kft. Light rain will be impacting all sites Monday morning, with breezy winds anticipated for KPDT/KRDM/KBDN/KALW. Gusts at these sites are likely to hover around 25 kts late Monday morning as a cold front passes the area. 75

PRELIMINARY POINT TEMPS/POPS

PDT 42 59 47 56 / 40 70 70 90 ALW 45 57 48 54 / 50 90 80 90 PSC 43 60 48 56 / 10 60 50 70 YKM 36 55 40 51 / 10 80 70 70 HRI 42 62 49 57 / 20 60 60 90 ELN 33 49 37 46 / 20 90 80 60 RDM 36 57 44 57 / 30 40 40 80 LGD 37 49 44 51 / 70 80 90 100 GCD 37 52 45 51 / 40 50 50 90 DLS 46 59 50 55 / 60 90 90 90

PDT WATCHES/WARNINGS/ADVISORIES

OR...Wind Advisory from 1 PM Monday to 7 AM PST Tuesday for ORZ041- 510.

Wind Advisory from 4 PM Monday to 7 AM PST Tuesday for ORZ044- 507-508.

WA...Wind Advisory from 1 PM Monday to 7 AM PST Tuesday for WAZ024- 521.

Wind Advisory from 7 PM Monday to 7 AM PST Tuesday for WAZ027>029.