textproduct: Pendleton

KEY MESSAGES

- Breezy gap winds today becoming light through Thursday with near to above normal temperatures each day

- Widespread light rain and Cascade peak light snow return Friday with breezy to locally gusty winds in the lower elevations

- Trough entering Sunday to continue bringing cooler temperatures throughout the region

DISCUSSION

Mostly quiet conditions across the region tonight as an upper low passes well to the south of the PacNW. Nighttime satellite imagery does show decks of cirrus draped across the forecast area, with a stratus decks west of the Cascades. At the surface, breezy winds have developed through the Cascade Gaps post a weak frontal passage yesterday.

Today through Friday: Through early Thursday, the forecast area will remain under a west to southwest flow aloft, promoting mostly quite conditions and near to above normal temperatures. However, a strong, deep low in the Gulf of Alaska will swing a cold front into the area today, which will reinforce breezy winds (15-25mph with gusts up to 35mph) through the Cascade gaps. Otherwise, a weak shortwave impulse and difluent flow aloft will promote a low chance (10-20%) of shower over elevated terrain from the Elkhorn Crest to the Wallowas this afternoon.

There is great agreement amongst ensemble and deterministic guidance that an upper trough in the northeast Pacific will swing into the PacNW with widespread showers late Thursday through Friday. In the lower elevations, surface pressure gradients will tighten Friday in response to a surface low moving inland with the trough axis. This will result in breezy to locally gusty westerly winds (15-30mph with gusts 35-50 mph) developing through the Cascade gaps and into the lower elevations (confidence 65-70%). Temperatures will be on a cooling trend with the trough passage, with afternoon high temperatures in the 60s to low 70s, and 50s in the mountains. Lawhorn/82

Saturday through Monday: As the shortwave begins to move northeast into the Canadian Provinces, there will be a shortwave trough entering from the Pacific into Southern Oregon to Mid/Southern California. Models are in agreement with offshore troughing Saturday morning into midday, but are in disagreement with the position and strength of the exiting trough from earlier in the week. The GFS members show the exiting trough more stronger and more northward. The Canadian and the European members display a stalling and more southward position, with the European being the strongest bringing breezy conditions to the Cascade Gaps Saturday morning(15% Confidence). There is moderate confidence (40% - 50% confidence) that the Offshore trough makes landfall through Sunday, bringing light precipitation along the Cascades. Near normal/ slightly below normal temperatures with moderate confidence (40% - 50% confidence), with mins in the high 40's and highs in the high 60's cooling from Saturday into Monday.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

DLS/PDT/RDM/BDN: VFR conditions to prevail through the period. Winds will increase to 15-20kts with gusts up to 30kts at site DLS this afternoon, then gradually decreasing until becoming light overnight. Sites PDT/RDM/BDN will see winds increase to 10-15kts with gusts to around 23kts developing in the afternoon, becoming light in the evening. Lawhorn/82

YKM/ALW/PSC: VFR conditions are to be present for all sites through the TAF period. Breezy conditions of gusts up to 18KT present at ALW from 16z to 04z. Variable wind directions are to be present at YKM from 21z to 01z and PSC from 07z to 12z.

Preliminary Point Temps/PoPs

PDT 76 45 74 48 / 0 0 0 0 ALW 77 52 75 53 / 0 0 0 0 PSC 80 48 77 48 / 0 0 0 0 YKM 79 48 74 48 / 0 0 0 0 HRI 78 49 76 48 / 0 0 0 0 ELN 70 43 69 44 / 0 0 0 0 RDM 75 38 73 39 / 0 0 0 0 LGD 79 44 77 47 / 0 0 0 0 GCD 80 44 79 47 / 0 0 0 0 DLS 74 51 77 51 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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