textproduct: Pendleton

KEY MESSAGES

- Weak warm front today

- High pressure returns Tuesday through Friday

- Likely pattern change by the weekend

DISCUSSION

Today, a weak warm frontal passage will cause snow levels to rise above mountain pass levels through the day. Prior to snow levels rising, light snow (trace to 2 inches) is forecast for the Washington Cascades. Outside of the Yakima and Kittitas valleys and northern Blue Mountains, measurable precipitation is not anticipated east of the Cascades.

Tuesday through Friday, ensemble clusters all show some flavor of an anomalously strong upper-level ridge over the Pacific Northwest. This pattern favors air stagnation, lowland stratus and fog, and warm mountain temperatures. Have included a mention of patchy fog in the gridded forecast through Thursday morning since confidence is high (80 percent) that there will be at least periods of fog in the Columbia Basin and surrounding lowlands. Also worth a mention, should widespread fog and stratus materialize, afternoon high temperatures will almost certainly fail to reach the NBM's optimistically warm values for areas affected by fog/stratus. Moreover, the NBM's cloud cover forecast is showing mostly SCT-BKN skies in the lowlands, but OVC conditions are more representative of what is typically observed in this pattern.

By next weekend, ensemble clusters show good potential for a return to an active winter pattern, though with ensemble membership at roughly a 60:40 split between a wetter troughing pattern and a drier ridging pattern, confidence in forecast details is low.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Aside from IFR CIGs this morning at DLS, anticipating VFR conditions as we await the arrival of a weak warm front later this morning. CIGs will lower later this morning through afternoon as the front crosses the region, though precipitation will be limited; temporary -RA is forecast at YKM, while ALW/PSC have PROB30 groups included. Elsewhere, did not include a mention of precipitation at DLS/PDT, with only 10-20 percent chances of -RA forecast. Unless FG manages to form this morning at RDM (confidence too low to include in the TAF), BDN/RDM will remain VFR through the period with only FEW to SCT mid- and high-level cloud.

Sustained winds will be mostly light at 10 kts or less.

Preliminary Point Temps/PoPs

PDT 36 51 33 50 / 10 0 0 0 ALW 38 50 36 51 / 10 0 0 0 PSC 33 50 34 50 / 10 0 0 0 YKM 33 49 34 50 / 10 0 0 0 HRI 34 50 34 49 / 10 0 0 0 ELN 33 44 33 46 / 20 0 0 0 RDM 28 58 27 58 / 0 0 0 0 LGD 34 55 36 54 / 10 0 0 0 GCD 32 57 33 57 / 0 0 0 0 DLS 37 52 37 50 / 10 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...None.