textproduct: Pendleton

KEY MESSAGES

1. Mountain rain will persist through Saturday over the OR Cascades and eastern mountains

2. Temperatures will return to near seasonal averages

3. Dry and cooler conditions through Monday night

DISCUSSION

Current radar shows a few returns over the Cascades and the Blues as the remnants of the atmospheric river remain over the area. Current ground observations show that the last hour these returns have only put down between 0.01-0.02 inches of rain. Rain is expected to continue over the mountains through today (Saturday) with rain accumulations nearing 0.05-0.1 inches in the OR Cascades and the eastern mountains through 11 PM tonight (70-90% confidence). Radar coupled with models show the majority of the perception will continue a southwest trajectory over the OR Cascades and Blue Mountains before tapering off Saturday night.

Models show a weak cold front moving across the region late last night and through this morning. This will bring with it increased cloud cover as well as cooler temperatures. In house comparisons show that temperatures will decrease nearly 20 degrees from yesterday with temperatures at or near seasonal normal. With that said, NBM raw ensembles as well as HREF raw ensembles show 80-90% confidence that the Basin, Yakima, the Gorge and central OR seeing temperatures in the mid to upper 50s Saturday while elsewhere will see upper 40s to low 50s with even cooler temperatures along the higher terrains. Sunday both raw ensembles sets show temperatures to be even cooler with 70-80% of the aforementioned areas seeing low to mid 50s with isolated locations in central OR and the Basin seeing mid to upper 50s. After Sunday, models show a slow warm up through the beginning of next week.

Models show persistent cool and dry weather through Monday night as southwest flow aloft continues over the area. This will slowly bring temperatures up through the beginning of the week. Models also show that precipitation will be lacking with the southwest flow keeping the region dry ahead of a pattern change with an upper level shortwave bringing in increased chances of precipitation, breezy winds and a return to cooler conditions.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

VFR conditions are expected through the TAF period. A cold front will cross the region through Saturday morning. Winds will again increase through the overnight hours with DLS/RDM/YKM all seeing sustained wind of 13-20 kts and gusts near 25kts. All other sites will see increased winds of 12kts or lower. -RA is occurring at PDT/PSC and ALW and will persist through 16-18Z with no concern for CIGs or VIS.

HYDROLOGY

The Cascade Slope basins have received the bulk of the precipitation that will be impacting river forecasts over the weekend. All tributaries with mountain headwaters will continue to run high. Forecast points along the Naches and Yakima Rivers will be the most impacted by the surge of mountain runoff as several of these points enter into flood by Saturday, if not already in flood like the Naches at Naches. The Yakima River at Easton is forecast to reach just over the 52.1 ft level, (about 1 ft over moderate flood) but has a 30% chance of reaching 52ft. At Kiona, the river is forecast to reach the 13.9 ft level, but has a 10% chance of reaching 14 ft. Russell/71

Preliminary Point Temps/PoPs

PDT 58 30 57 33 / 80 0 0 0 ALW 58 34 57 37 / 90 0 0 0 PSC 64 33 60 34 / 50 0 0 0 YKM 58 29 56 33 / 0 0 0 0 HRI 62 32 60 33 / 70 0 0 0 ELN 50 29 52 30 / 0 0 0 0 RDM 59 24 60 29 / 20 0 0 0 LGD 56 28 58 34 / 80 0 0 0 GCD 58 29 60 35 / 60 0 0 0 DLS 60 34 61 37 / 10 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...None.