666 FXUS66 KOTX 022217 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 217 PM PST Sat Jan 2 2021 .SYNOPSIS... This weekend through next week will feature several rounds of lowland rain mixed with snow at times while the mountains continues to accumulate snow. Heavy mountain snow will be possible over the weekend with windy conditions picking up Saturday night into Sunday. The weather will likely remain active into next week as several storms push through the region. The system on Monday will deliver widespread snow at least above 3000 feet while another on Wednesday could deliver the best chance of valley snow to many locations. && .DISCUSSION... ...HEAVY SNOW IN THE MOUNTAINS WITH WET...MILD AND WINDY CONDITIONS RESULTING IN SNOW MELT IN LOW LANDS THIS WEEKEND... Tonight through Sunday night: A mild atmospheric river will remain aimed at the region through early Sunday bringing valley rain and mountain snow, as well as mild and windy conditions tonight resulting in lower elevation snowmelt. Drier air behind the front should bring clearing to the area on Sunday except for lingering snow showers near the Cascade crest. The next system begins to push in late Sunday night. Below summarizes expected impact into Sunday. Mountain snow: Heavy accumulations remain in the forecast above 4000 feet mainly near the Cascade crest and in the Idaho Panhandle where strong westerly flow will enhance upward motion and precipitation amounts in these areas. Snow levels are just high enough this evening around Stevens Pass that snow may have a harder time accumulating until overnight as snow levels drop. The Central Panhandle Mountains should accumulate snow through the night with heavy accumulations including Lookout Pass. Winds: Winds remain a concern tonight as 850mb winds ahead of the cold front increase to near 60 kts over SE WA into the ID Panhandle but since this is in the warm sector mixing potential should be low. Still a tight south to north pressure gradient may bring sustained winds close to advisory criteria in the Columbia Basin and West Plains. Then with the cold front passage 35-45 MPH wind gusts could mix down early Sunday morning with the most likely area stretching from SE Washington into the central and southern ID Panhandle up into the Spokane and Coeur d'Alene areas. Right now it looks like advisory strength winds will be localized and brief given the limited mixing so opted to not issue any wind advisories. Rain/Snowmelt: The mild and windy weather will result in increased snow melt especially across the palouse up into the Spokane/Coeur d'Alene area. Around 0.4-0.70 inches of rain over the eastern third of WA and the Palouse will add further to rises on small streams with higher precip amounts of 1-1.50 inches in the Central Panhandle Mountains. Given this is a brief rain event and that snow levels only rise to near 3500-4000 feet confidence in flooding is not high. Although local issues are possible especially in poor drainage areas. Will continue the Hydrologic Outlook for Spokane, Kootenai, Whitman, Latah, and Benewah counties. JW Sunday Night and Monday: A quick moving system will push through the region from the South bringing another round of precip of to the region. Timing is going to be key on determining impacts for the region. A warm front will bring a decent amount of moisture into the region. It will continue to be mountain snow. The Northern Valleys have become a tricky part of the forecast. The amount of snow for the valleys hinges on when the warm air moves in and changes the snow to rain on Monday. The Columbia Basin is expected to start is snow late Sunday night and transition to mainly rain by late Monday morning. With the snowmelt from warmer temps and breezy winds and precip amounts of a few tenths of an inch, localized hydro issues could be problem. Snow amounts for the period are expected to be around an inch for the Columbia Basin through the Monday AM. The Northern Valleys could see amounts in the range of 3 to 6 inches depending on how quickly the warmer surface air moves into the area. The mountains can expect 10 to 14 inches through Monday night with about 5 inches through Monday AM. Overnight snow could lead to Monday AM commute issues. Tuesday through Friday: A ridge will be over the region late Monday and Tuesday creating a dry, stable pattern. Models are indicating the next Low system will begin to press into the region late Tuesday, early Wednesday and linger through Thursday. It could be another widespread snow event. Models are in poor agreement with the moisture with the system. There is low confidence on the impacts. A brief break is expected Friday before another system over the weekend. Temperatures from Sunday through Friday are not expected to vary much as the steady stream of systems will keep cloudy skies. Highs for the period will generally be in the low 40s to 30s. Lows will range from upper 20s to 30s. /JDC && .AVIATION... 18Z TAFS: The next weather system will be pushing in through tonight bringing rain and mountain snow mainly to the ID Panhandle and eastern third of Washington and near the Cascade crest. Increasing southerly boundary layer winds may aid in keeping the boundary layer from completely saturating from the Spokane area down to the palouse as well as the Columbia Basin with Walla Walla currently showing a larger temp/dew point spread indicative of the drier boundary layer in this area. Winds will peak late tonight with the front passage with surface wind gusts near 40 kts expected at KGEG. The East Slope Cascade valleys should remain sheltered from the winds including KEAT until after the cold front passage Sunday morning. JW && .PRELIMINARY POINT TEMPS/POPS... Spokane 37 42 32 40 31 38 / 90 40 40 90 60 10 Coeur d'Alene 37 41 31 39 31 36 / 100 80 40 90 70 10 Pullman 38 42 33 42 32 39 / 90 70 50 90 60 10 Lewiston 42 50 37 47 37 46 / 40 30 30 80 60 10 Colville 36 43 31 38 28 36 / 90 10 40 90 60 0 Sandpoint 36 40 30 36 30 35 / 100 90 30 100 90 20 Kellogg 36 39 30 40 32 35 / 100 100 30 90 90 30 Moses Lake 35 47 35 45 33 42 / 20 0 70 80 20 0 Wenatchee 33 45 32 38 31 37 / 10 0 90 90 30 10 Omak 33 42 30 38 28 36 / 50 0 70 80 40 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Winter Storm Warning until noon PST Sunday above 4000 feet for Central Panhandle Mountains. WA...Winter Weather Advisory until 10 AM PST Sunday for the cascade crest including highway 2 between coles corner and stevens pass for East Slopes Northern Cascades. && $$