textproduct: Pendleton

KEY MESSAGES

- Above-normal temperatures this weekend into early next week.

- Low (5-15 percent) chance of thunderstorms Monday.

- Uncertainty in pattern details Tuesday and beyond.

DISCUSSION

An upper-level ridge continues to build over the Pacific Northwest early this morning, and mostly clear skies are evident on satellite imagery. Ensemble NWP guidance is in excellent agreement that the ridge axis will continue to shift northeast through the weekend, with the axis overhead by Sunday, resulting in very high confidence (95 percent) that temperatures will warm to above normal. From a deterministic standpoint, widespread 70s, and isolated lower 80s, are advertised by the NBM for Sunday and Monday. Glancing at probabilistic output, there is a medium-high (50-95 percent) chance the eastern Columbia River Gorge, Yakima Valley, lower Columbia Basin, and lower elevations of north-central and central Oregon will reach 80 degrees Monday.

Dry conditions are expected (95 percent confidence) under the ridge through the weekend, but guidance is showing low (10-20 percent) chances of showers and very low (5-15 percent) chances of thunderstorms Monday as a weak shortwave wriggles into the Pacific Northwest and interacts with what long-range CAMs are showing as a weakly unstable environment (MUCAPE <500 J/kg) over the mountains (primarily the Blues, but also portions of the Cascades of both Oregon and Washington).

There is significant uncertainty in pattern details Tuesday through the remainder of the week. To give a broad overview, ensemble guidance generally depicts a closed low in the Pacific approaching the OR/CA coast while a second closed low and secondary shortwave trough dive down from Canada across either the Northern Tier (roughly 60 percent of members) or farther south into the Pacific Northwest (roughly 40 percent of members). Temperatures would be near or below normal should the latter scenario materialize. Right now, winds on Tuesday are the best chance of a headline-worthy event. The NBM suggests a low- medium (30-60 percent) chance of reaching or exceeding advisory-level wind gusts (45 mph or greater) through the Cascade gaps and across wind-prone portions of the Columbia Basin and surrounding lowlands.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Confidence is high (90 percent) that VFR conditions will persist through the period, albeit with increasing mid- and high-level clouds by Sunday. Winds will be diurnally and terrain-driven, sustained at 10 kts or less for all sites. Gusts of up to 15 kts are most likely at RDM/BDN this afternoon and evening. 86

Preliminary Point Temps/PoPs

PDT 68 41 72 45 / 0 0 0 0 ALW 67 45 72 50 / 0 0 0 0 PSC 70 40 75 46 / 0 0 0 0 YKM 69 42 72 45 / 0 0 0 0 HRI 70 41 74 46 / 0 0 0 0 ELN 64 40 68 44 / 0 0 0 0 RDM 71 36 75 39 / 0 0 0 0 LGD 66 39 69 43 / 0 0 0 0 GCD 68 38 71 42 / 0 0 0 0 DLS 71 46 74 49 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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