textproduct: Pendleton

AVIATION...00z TAFs

Variable conditions will materialize this evening as another round of rain showers develop over primarily the Basin and adjacent valleys. MVFR conditions are possible (40-50% chance) under rain showers. BDN and RDM are largely expected to be spared of rain through the period, outside of trace amounts. Once rain tapers off by around midnight, winds will start to pick up by sunrise Wednesday. Gusts could reach 30 kts at many sites, possibly as high as 40 kts in sites across the Basin (30-40% chance). Cigs will transition from low to mid bkn-ovc this evening to sct-bkn mid cigs during the day tomorrow. 74

PREV DISCUSSION

/issued 242 PM PST Tue Dec 9 2025/

Key Messages...

- Excessive Rainfall in the elevated category across the Washington Cascades with numerous flooding impacts continuing . - Breezy to Windy conditions beginning overnight and lasting though Thursday.

- Warmer than normal temperatures are expected in the extended periods.

DISCUSSION...

The synoptic setup shows a trough of low pressure lifting into BC as a warm front spreads north across WA/OR Today. An Atmospheric River will remain relevant to the sensible weather Tonight, lifting northward and spreading more rain along the frontal boundary. As the AR weakens Tonight and Wednesday , precipitation will become more relegated to the Cascade Caps and eastern Mountains, continuing to aggravate the recent onset of flooding across the Yakima Valley.

Additional river flooding risk will continue along rivers of the Yakima valley Tonight as excessive rainfall across the Washington Cascades remains in the elevated category. This is due to a combination of runoff from rains along the lowers lower slopes of 1 to 2 inches and several inches from the Upper Slopes.

Breezy to windy conditions are anticipated across the entire area as a warm front lifts across the area Tonight. The potential for sustained winds greater than 30 mph ramps up to around 60-80 percent by the overnight hours. This will bring the need for wind advisories focused large on the lower Columbia Basin of WA, the Simcoe Highlands as well as the Foothills of the Northern Blues. The advisory has been issued for these areas beginning 6 am Wednesday and lasting through 9 am Thursday.

Temperatures with the westerly flow will be markedly warmer in the lowlands of the Columbia Basins and central Oregon/John Day basin, and typically well into the 60s Wednesday and into Thursday.

The AR weakens with midweek, however enough moisture transport appears available to maintain and slight risk (15% chance of exceeding flash flood guidance) west of a line from Wenatchee to Hood River through the day on Wednesday. Risk ramps down on Thursday, but a 5% chance for these conditions persist for the Upper Slopes. An areal flood watch is in place for much of Kittitas, Yakima and Klickitat counties through Friday morning. Russell/71

PRELIMINARY POINT TEMPS/POPS

PDT 46 64 51 61 / 90 40 10 20 ALW 48 63 53 60 / 100 60 20 40 PSC 46 65 54 63 / 100 20 10 20 YKM 41 63 48 59 / 100 60 50 40 HRI 46 66 53 62 / 90 20 10 20 ELN 37 58 43 52 / 100 70 60 60 RDM 44 62 36 59 / 50 10 0 10 LGD 43 59 46 56 / 100 50 10 30 GCD 45 58 39 56 / 80 10 0 10 DLS 48 63 53 61 / 100 70 70 60

PDT WATCHES/WARNINGS/ADVISORIES

OR...Wind Advisory from 6 AM Wednesday to 7 AM PST Thursday for ORZ041-044-507-508-510.

WA...Wind Advisory from 6 AM Wednesday to 7 AM PST Thursday for WAZ024-027>029-521.

Flood Watch through Friday morning for WAZ026-027-521>523.