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 /18Z TAFS THROUGH 18Z WEDNESDAY/

Broad westerly surface winds and no risk of ceilings or visibility restriction for local terminals over the TAF period. A few locations like RDM/BDN/DLS can have stronger winds and gusts in the later afternoon due to gap winds. A ramp up in north wind speed at BND between about 21z and 00Z as downslope influences winds, keeping conditions gusty through around 3 or 4z. Any gusts at ALW should be occasional and short lived early this afternoon, while YKM and PSC remain light (under 12 kts).

Preliminary Point Temps/PoPs

PDT 77 45 74 46 / 0 0 0 0 ALW 78 51 75 52 / 0 0 0 0 PSC 82 49 77 48 / 0 0 0 0 YKM 81 48 74 49 / 0 0 0 0 HRI 80 49 77 48 / 0 0 0 0 ELN 72 44 69 44 / 0 0 0 0 RDM 74 38 74 40 / 0 0 0 0 LGD 77 44 77 47 / 0 0 0 0 GCD 80 44 80 48 / 0 0 0 0 DLS 75 50 77 52 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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