textproduct: Pendleton

KEY MESSAGES

- Showers and breezy conditions remain through this afternoon and into the evening hours.

- Wind advisories are still in effect this afternoon from the Kittitas and Yakima Valley's to the Lower Columbia Basin.

- Dry and light wind conditions return over the weekend; low chance for freezing temperatures Saturday near Wallowa Valley.

DISCUSSION

Current satellite and radar imagery show showers impacting our forecast area as the surface low moved onshore this morning. This system brought bands of light rain to the eastern slopes of the Cascades, with some showers still present in the central and northeast portions of the forecast area.

Showers and breezy conditions should diminish later tonight as the upper-level trough exits further northeast out of our forecast area. Post-frontal showers will continue this afternoon into the early evening hours and the breezy wind conditions should die down and become more light by early Saturday morning. Deterministic and ensemble guidance continue to be in good agreement of a weak broad shortwave developing offshore the PacNW along the California coast Saturday morning, then gliding through the area over Sunday (confidence 75-80%). Although probabilistic guidance depicts some vorticity advection aloft associated with the upper-level trough, there doesn't seem to be efficient moisture and low-level jet flow favoring the development of precipitation for our area (confidence 50-60%).

Model guidance continues to support below normal temperatures this weekend across the region, with afternoon high in the low-mid 60s Saturday and high 60s to low 70s Sunday. Per HiRes models, there is a low chance for freezing temperatures in and near Wallowa Valley, but looks to be confined to the Wallowa Mountains(confidence 15- 20%).

For Monday, probabilistic guidance is in good agreement that mostly zonal flow will return over the PacNW bringing dry and light wind &&

conditions to the forecast area. While an upper-level trough and attendant low-pressure system develops in Alaska and northern British Columbia which, per model guidance, should stay more northwest of the PacNW. Along with this trough is some embedded shortwaves which might bring precipitation chances Tuesday as it shifts southeastward(confidence 65-80%). Ames/01

Tuesday through Thursday: Models show the synoptic pattern to be in a more zonal flow regime. A shortwave will move through the zonal flow bringing mountain showers and breezy conditions Tuesday. 60-80% of the raw NBM ensembles show there to be a 60-80% chance of another 0.10-0.25 inches of rain along the central WA Cascades Tuesday. Not only will there be mountain rain, but models show a slight tightening of the pressure gradients at the surface. This will bring breezy conditions through the Columbia Gorge as well as along the foothills of the southern Blues. NBM raw ensembles show a 60-70% probability of seeing sustained winds near 15 mph with gusts to near 30 mph.

Wednesday models show the potential for some lingering showers along &&

the Cascades before the synoptic pattern begins to shift by Wednesday afternoon. 40-60% of the NBM raw ensembles show an additional 0.05-0.10 inches of rain through Wednesday afternoon. By Wednesday afternoon, models show the leading edge of the next system beginning to dig southwards into the region. However, the models begin to differ in what that system will ultimately be. EURO remains with zonal flow through Thursday while the GFS brings in the leading edge of a trough. Either solution shows temperatures to be at or slightly below normal with cooler temperatures through Thursday and dry conditions. 90

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

VFR conditions prevail. Winds are still gusty but winds are trending down overall thoughout the region. An occational gust in the higher elevations cannot be ruled out. Tomorrow winds should be relatively calm with speeds under 10 kts with little to no impactful gusts forecasted at this time.

KPSC is urrently under a Airport Weather Warning untill 5pm PDT. Highest winds so far around 51 mph/44 kts

Preliminary Point Temps/PoPs

PDT 39 64 37 65 / 0 0 0 0 ALW 45 65 42 66 / 0 0 0 0 PSC 42 68 41 71 / 0 0 0 && 0 YKM 40 64 41 67 / 0 0 0 0 HRI 42 67 40 69 / 0 0 0 0 ELN 36 60 36 63 / 10 0 0 0 RDM 32 63 33 63 / 0 0 0 0 LGD 37 64 38 68 / 0 0 0 0 GCD 37 67 40 70 / 0 0 0 0 DLS 45 68 45 71 / 10 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 11 PM PDT this evening for WAZ024-027>029- 521. OR...Wind Advisory until 11 PM PDT this evening for ORZ041-044-507- 508-510. Wind Advisory until 5 PM PDT this afternoon for ORZ511.