textproduct: Pendleton

KEY MESSAGES

- Widespread breezy to locally windy conditions tonight, strongest in the Kittitas Valley where a Wind Advisory remains in effect until 7 AM PDT

- Morning showers in eastern portions of the Columbia Basin tomorrow

- Below-normal temperatures, breezy to locally windy west winds, and occasional light mountain showers through the week

SECOND EVENING UPDATE

Windy conditions persist through the Kittitas Valley, and are expected to continue through the night so have opted to extend the Wind Advisory until 7 AM PDT.

EVENING UPDATE

A strong cross-Cascade pressure gradient has persisted this afternoon, peaking thus far at a 13-mb difference between PDX (Portland) and GEG (Spokane). Widespread breezy to windy westerly winds of 20-35 mph with gusts of 35-45 mph have expanded eastward across north-central Oregon, the lower Columbia Basin of Oregon, and the foothills of the Blue Mountains of Oregon. Have opted to expand the Wind Advisories to include the aforementioned zones through 11 PM this evening.

DISCUSSION

Water vapor satellite imagery this afternoon shows a closed low centered along the MT/Alberta/Saskatchewan border, which facilitated a shortwave passage over the forecast area earlier today. Showers associated with this shortwave continue to push south across Wallowa, Union, and Grant counties this afternoon, with shower activity expected to diminish by early this evening. Otherwise, a surface low strengthening under the upper low has resulted in a tightening cross-Cascade pressure gradient, with breezy to locally windy westerly winds (15-30 mph with gusts 25-45 mph) spilling through the Cascade gaps and into the lower elevations. The strongest winds so far have been noted in portions of the Kittitas Valley and the eastern Columbia River Gorge, with gusts up to 50 mph and sustained winds around 30 mph.

Monday through Thursday: A prolonged troughing pattern supported by periodic shortwave passages will remain over the PacNW through the workweek. The upper low will continue to meander east tonight through Monday, with the next round of shower activity expected to arrive across the eastern third of the forecast area with a shortwave passage late tonight through tomorrow morning. There is increasing confidence (55-75%) that showers will also impact eastern portions of the Columbia Basin (including Tri-Cities and Hermiston) tomorrow morning, with heaviest showers expected along the WA Blue Mountain foothills.

Cluster ensemble guidance remains in good agreement of a shortwave trough diving down the AK/BC coastlines and across the PacNW Tues/Wed which will bring another round of light mountain rain showers (confidence 55-75%). Another shortwave trough is advertised to drop into the PacNW Thursday, however, over the last 24 hours, ensemble and deterministic guidance has trended drier with this system. Confidence in another round of light mountain showers for Thursday is low-mod (30-45%).

Breezy winds will remain in place across the lower elevations and Cascade gaps through much of the work week as the troughing pattern persists overhead. After today, winds will generally be between 15-25 mph with gusts up to 40 mph throughout the week.

Lastly, the persistent trough pattern will keep temperatures much cooler than normal through the week, with afternoon temperatures generally 5 to 15 degrees below normal (confidence 60-75%). This means that afternoon temperatures in the lower elevations will be in the 70s, with locally 80s, throughout much of the week. In the mountains, mid-elevations will generally be in the upper 50s to 60s, with lower to mid 50s in the high- elevations.

Friday and Saturday: Late Friday into Saturday, ensemble cluster guidance is in agreement of the upper trough pushing east, with a quasi-zonal flow and weak upper level high pressure developing over the PacNW (confidence 40-65%). This will result in a warming trend into near to above normal temperatures across the forecast area (80s in the lower elevations, 60s and 70s mountains) with dry conditions and light winds by Saturday. Lawhorn/82

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Predominantly VFR conditions and periods of breezy winds are forecast for the next 24 hours. A band of light rain is forecast to continue spreading southwest overnight into Monday morning, affecting sites ALW/PDT/PSC, and perhaps YKM. ALW has the best chance of sub-VFR CIGs and included a mention of MVFR conditions towards morning in light rain.

Preliminary Point Temps/PoPs

PDT 53 75 52 76 / 10 50 10 0 ALW 54 76 57 77 / 70 80 10 10 PSC 57 81 58 82 / 20 50 10 0 YKM 59 83 56 83 / 10 20 10 0 HRI 55 79 56 79 / 0 40 10 0 ELN 54 75 53 74 / 20 20 0 0 RDM 42 72 41 74 / 0 0 10 0 LGD 50 70 50 75 / 30 80 10 10 GCD 46 72 48 77 / 0 20 10 0 DLS 57 73 56 72 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 7 AM PDT Monday for WAZ026. OR...None.