207 FXUS65 KBOI 042137 AFDBOI Area Forecast Discussion National Weather Service Boise ID 237 PM MST Sat Dec 4 2021 .SHORT TERM...Tonight through Monday night...Cold front across WA is approaching the region from the northwest. Temperatures have risen into the low to mid 60s across the plateaus of eastern OR. Patchy fog remains in the lower Treasure Valley near Ontario, but should clear out by this evening. Scattered snow showers expected later this evening as the cold front moves through, mainly across the mountains. Outside of the mountains, conditions will generally be dry with a few sprinkles. The front will bring breezy west to northwest winds this evening through Sunday afternoon. Winds will slowly subside during the afternoon, and become light after sunset. Temperatures will be around 10 degrees cooler on Sunday with mostly sunny skies. A system will arrive on Monday with precipitation expected across most of the region. Snow levels will initially be at the surface at all locations, before rising to around 4000-5000ft MSL Monday afternoon. So may see light snow initially in the Treasure Valley before changing over to rain. QPF trends with this system continue to trend downward with about a 50 percent drop across the board from yesterdays model suite. The mountains could see 3-6 inches of snow with generally under an half inch in the lowest valleys. .LONG TERM...Tuesday through Saturday...Active weather will dominate through the period. Northwest flow over the area on Tuesday may bring a few snow showers to the northern mountains. Embedded shortwaves in a deepening trough over Canada and the U.S. will bring a chance of precipitation to the forecast area Wednesday into Friday with much colder air arriving. Snow levels Wednesday from 4000 feet across the north and 6000 feet across the south, will lower to the valley floors by Thursday. The upper level trough is expected to move east of the area Friday night and Saturday bringing drier conditions with lingering snow showers across the northern half of the forecast area. && .AVIATION...VFR will prevail tonight and Sunday across southwestern Idaho and Southeastern Oregon. Expect isolated to scattered rain and snow showers with mountain obscuration tonight and early Sunday morning north of a line from KBKE to KSUN. Surface winds: variable 5- 10 kts across the Treasure Valley as well as KMYL and KBKE areas, becoming northwest 10-15 kts with gusts to 20 kts overnight and Sunday. Elsewhere, surface winds southwest 10-15 kts with gusts to 25 kts becoming becoming northwest 10 to 20 kts with gusts to 30 kts overnight and Sunday. Winds aloft at 10k ft MSL: west to northwest 35-50 kts. && .AIR STAGNATION...A cold front will end the air stagnation advisory this evening. Expect good ventilation and sufficient mixing by this evening. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Air Stagnation Advisory until 5 PM MST this afternoon IDZ011-012-014-033. OR...Air Stagnation Advisory until 5 PM MST /4 PM PST/ this afternoon ORZ061>064. && $$ www.weather.gov/Boise www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...KA LONG TERM....TL AVIATION.....TL AIR STAGNATION...KA