textproduct: Pendleton

KEY MESSAGES

- Hydro concerns continue for the next several days, mostly confined to the Naches and Yakima rivers.

- Valley rain today, with drying conditions later this week.

- Breezy to locally windy conditions develop today and Wednesday along the Columbia Basin through the Simcoe Highlands.

DISCUSSION

An atmospheric river continues to deliver rain/snow in the Cascade mountains that will trail through the Columbia Basin later Tuesday morning/afternoon. Chances of rain across the Columbia Basin will increase as we go through the later morning hours going into the afternoon. Areas across the Basin will see values around the .1" range (60-80% chance), while the mountain crests will see a half inch to inch through Wednesday (70-90% chance). Snow levels will be above 9000 feet through Wednesday morning until a cold front sweeps through the region, dropping levels to 2500-3500 feet. Rain will transition into snow as a result, with light to locally moderate rates in many parts of the mountain region.

Breezy to locally windy conditions will develop as the front sweeps the region, bringing 25 to 35 mph gusts across the Basin, with higher 35-40+ mph gusts in higher elevations. Strongest winds are forecasted to develop late Tuesday morning through the afternoon hours. Winds will decrease going into the early Wednesday morning hours, with a secondary maxima developing in the Wednesday afternoon timeframe. Widespread advisory confidence is currently low (20-40% chance), with close monitoring needed for future trends. NBM currently shows 20-40% chances of many places in the Basin reaching above criteria Tuesday and Wednesday. Wednesday appears to show slightly stronger winds compared to Tuesday.

Ridging will develop Friday, bringing dry conditions into the area, along with a warming trend going into the weekend. High temperatures from the NBM currently forecasts max temperatures to re-enter the high 60s to low 70s (70-90% chance) by Sunday. Guidance shows a wetter pattern returning going into early next week, with light mountain showers and lower elevation rain as deterministic models bring a trough from the Pacific onshore by the Monday/Tuesday timeframe.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

VFR conditions are likely (80-95 percent, varying by site) today at all sites. Overnight into Wednesday morning, chances of MVFR CIGs increase to 20-50 percent at PDT/ALW, with low (20 percent or less) chances elsewhere.

Periods of light rain are forecast at all sites today as a front moves through the region.

Southwest winds of 15-25 kts with gusts of 25-35 kts are forecast (80 percent confidence) at RDM/BDN/YKM today, with lower confidence (30 percent) in these winds mixing down into PSC. Elsewhere, winds are expected to be lighter at 5-15 knots. 86

Preliminary Point Temps/PoPs

PDT 66 43 56 30 / 70 80 40 10 ALW 63 45 56 34 / 90 90 60 20 PSC 65 43 62 33 / 60 40 10 0 YKM 63 35 56 28 / 70 20 10 0 HRI 66 43 60 32 / 60 50 20 0 ELN 54 33 49 28 / 80 20 30 10 RDM 66 37 54 21 / 40 50 10 0 LGD 65 44 53 28 / 70 90 70 30 GCD 69 47 60 26 / 40 60 40 10 DLS 60 42 57 34 / 90 70 30 10

PDT WATCHES/WARNINGS/ADVISORIES

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