textproduct: Pendleton

KEY MESSAGES

- Light to moderate rainfall with breezy to locally windy conditions will continue through the late afternoon to evening hours across parts of the Columbia Basin and Blue Mountains.

- Hydro concerns along the Naches and Umatilla Rivers.

- A drier and warmer pattern is expected Thursday!

DISCUSSION

Current radar shows a line of light to moderate rain continuing to fall in the Columbia Basin down through the Blue Mountains. The Kittitas and Yakima Valleys have dried out for the rest of night with the line advancing ahead, though windy conditions persist with 40-50 mph gusts prevailing across the Kittitas through the evening hours. Near the Northern Blue Mountains, strong orographic lift has enabled continuous moderate rainfall embedded with gusty 35-45 mph winds through the morning to afternoon hours. Observations from the past 12-hours shows that multiple sites already received 1 inch or greater of precip that include Meacham, Boiling Point, and Emigrant Springs. High confidence (>90% chance) that the Northern Blues will see at least an additional 1.7 to 2.7 inches of precip through tonight with the HREF 24-hour precip showing 1.3 to 1.5 inches in the 25th percentile. At the 75th percentile that jumps to 1.7 to 2.2 inches. Winds will continue to be breezy to locally windy across the OR Foothills, Kittitas Valley and Blues with winds decreasing below advisory level in the later evening hours (>90% confidence).

Synoptically, a ridge protruding into the PacNW & British Columbia area in a sideways rex pattern will tapper down PoP's through early next week. Model cluster support a cutoff low in the Alberta area will bring the area in-between the two systems with the ridge keeping most of the region dry while the low to the east will bring light snow showers into the Wallowa's and parts of the Northern Blues. All of the LREF clusters tell a similar story through early next week with keeping the Columbia Basin dry with some light snow showers and rain across the mountainous regions (that includes Central Oregon). Not seeing anything in the way of any major impacts or highlights through early next week at this time with the ridge still present and preventing any major QPF systems to develop.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Conditions range from VFR (most areas) to MVFR and even some IFR across the region as low pressure and rain impact the area. Latest radar imagery showed the back edge of the precipitation has made it through PSC and was working its way S and E. Conditions are expected to improve this evening.

Winds will continue to gust, but will gradually lessen and most locations will be around 10 kts by morning, with DLS being the only exception.

The other story is the gusty winds, mainly from the southwest to northwest across the TAF sites. These winds have beens as high as 40 to 45 kts across the region. Winds will remain gusty through the afternoon and evening hours before decreasing somewhat overnight. However, winds in the 15 to 25 kt range will be prevalent through the overnight hours.

HYDROLOGY

Rainfall has been less than forecast but has still been substantial. Rain amounts have been up to 2 inches in the Blue Mountains and up to an inch in the Blue Mountain Foothills so far and another half inch to inch of rain is possible through this evening. This has caused streams and rivers to rise. The Umatilla River at Gibbon is forecast to approach moderate flood stage this afternoon, though with reduced rainfall amounts, confidence is low to medium (30%-40%) of approaching moderate flood stage. Confidence is 70% to 80% that the Umatilla at Gibbon will reach minor flood stage. The Umatilla River at Pendleton is forecasted to reach minor flood stage by a few inches briefly between 9 PM and 5 AM tonight. Confidence is only about 50% of this happening. The Grande Ronde River at Troy, the John Day River at Service Creek and the Walla Walla River at Touchet River are all expected to exceed bankfull tonight and tomorrow. The first two only exceed it by a few inches. The Walla Walla River at Touchet gets to within a half foot of minor flood stage, but with rainfall trending lower than anticipated, do not believe it will reach minor flood stage. Elsewhere, the forecast for the Naches River at Cliffdell has been lowered to just below action stage. The Naches River at Naches is forecast to get about a half foot above bankfull tomorrow morning but should not cause any significant flooding. 83

Preliminary Point Temps/PoPs

PDT 39 59 38 56 / 40 20 20 10 ALW 42 59 39 57 / 50 40 30 20 PSC 42 66 40 63 / 20 20 10 0 YKM 39 67 40 60 / 0 0 10 0 HRI 40 64 39 60 / 20 10 10 0 ELN 39 60 35 57 / 0 0 10 0 RDM 26 62 29 59 / 10 0 0 0 LGD 36 54 35 51 / 90 30 50 20 GCD 31 56 32 53 / 80 0 10 10 DLS 41 66 42 64 / 10 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 11 PM PDT this evening for WAZ024-026-029- 521. Flood Watch through Thursday evening for WAZ029. Winter Weather Advisory until 8 PM PDT this evening for WAZ030. OR...Wind Advisory until 11 PM PDT this evening for ORZ041-044-507- 508-510. Flood Watch through Thursday evening for ORZ502-507-508. Winter Weather Advisory until 8 PM PDT this evening for ORZ502- 503.