textproduct: Pendleton

KEY MESSAGES

- Scattered mountain showers through Wednesday morning

- Breezy to windy conditions through this evening, with breezy conditions Wednesday

- Warmer, drier conditions Thursday through the weekend

DISCUSSION

Today through Wednesday: Showers have retreated to the mountains this afternoon as an upper trough swings into northern ID and MT. Partly cloudy to cloudy conditions are evident across much of the forecast area, though some "clear" pockets have develop across portions of central OR and the Horse Heaven Hills. Breezy winds also continue across much of the area post a cold front passage this morning, with some "exposed" stations having recorded gusts 45mph or over so far.

Today, shower activity will continue across mountain areas as northwest flow aloft develops behind the trough axis exit. Weak instability will develop across far northeast OR and southeast WA late this afternoon, resulting in a slight chance (10-20%) of isolated thunderstorms. However, thunderstorm activity is expected to diminish early this evening as the trough lifts further into MT. Otherwise, widespread breezy southwest to west winds (15-25 mph with gusts up to 40 mph) will continue into this evening behind a cold front passage from earlier this morning. In the lower elevations, stronger periodic gusts to around 45 mph and sustained winds up to 30 mph will continue to impact areas of the Columbia Basin, Blue mountain foothills, and in portions of the Kittitas valley.

By Wednesday, the trough will slide further east of the region while upper level ridging will develop over the northeast Pacific. Any lingering shower activity over the mountains will diminish by the late morning as a shortwave rounding the trough exits to the east and the region comes under the influence of the upper ridge offshore. Breezy to locally breezy winds will continue into Wednesday evening, but will become light Wednesday night into Thursday.

Thursday through Monday: There is good agreement amongst ensemble guidance that the PacNW will be under the influence of an upper level ridge in the northeast Pacific through early next week. Conditions across the area will trend drier and warmer, with the peak of the heating corresponding with the upper level ridge axis drifting closer to the PacNW (confidence 60-70%). Per the NBM, chances of reaching 90 degrees have dropped to 15-30% for Saturday across portions of the Columbia Basin, with Sunday showing 35-60% chance, and Monday a 45-85% chance across most of our lower elevation locations. While winds would generally trend light through this period, ensemble guidance is in good agreement in locally breezy conditions developing Saturday and Sunday as a shortwave trough dives down the northern Rockies (confidence 65-70%). This would bring elevated fire weather conditions across the Columbia Basin into portions of Central OR and the OR Cascade east slopes over the weekend, with the NBM showing a 30-50% chance of critical wind/RH criteria (RH < 25% and winds > 15 mph) being met. Lawhorn/82

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

VFR conditions to prevail through the period. Breezy winds (15-25kts with gusts up to 40kts) will impact sites into this evening, with winds weakening late this evening and overnight. However, winds 12-17kts will persist at sites DLS/PDT/ALW/PSC overnight. Expect winds to increase again and gusts to return between 14Z-18Z at all sites tomorrow. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 43 68 41 78 / 10 10 0 0 ALW 47 69 46 78 / 20 20 0 0 PSC 45 75 43 82 / 0 0 0 0 YKM 43 74 44 81 / 0 0 0 0 HRI 44 72 43 81 / 0 0 0 0 ELN 39 64 40 76 / 10 0 0 0 RDM 34 67 34 81 / 0 0 0 0 LGD 41 63 37 77 / 30 50 0 0 GCD 37 65 35 81 / 0 0 0 0 DLS 49 70 46 81 / 10 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 11 PM PDT this evening for WAZ024-026>029- 521. OR...Wind Advisory until 11 PM PDT this evening for ORZ041-044-507- 508. Wind Advisory until 5 PM PDT this afternoon for ORZ510.