254 FXUS65 KBOI 190344 AFDBOI Area Forecast Discussion National Weather Service Boise ID 844 PM MST Thu Feb 18 2021 .DISCUSSION...Main band of precipitation is moving across central and eastern OR this evening with moderate snow seen on webcams. Snow is increasing across southwest Idaho. Expect brief rain at the onset of precipitation, changing over to snow as the temperatures fall below freezing. Expect 1 to 3 inches across the lower valleys with 3 to 8 inches across the mountains with this system. Snow will generally taper off early Friday morning, with isolated snow showers. Then a threat of moderate to heavy snow/graupel showers possible Friday afternoon, with rain below 4000ft. Wouldn't be surprised to see an isolated thunderstorm on Friday afternoon and evening. May see some moderate accumulations over the mountains with this feature, that will need to be addressed in the upcoming forecast. && .AVIATION...Widespread snow and IFR conditions in southeast Oregon this evening, crossing southwest Idaho overnight. Conditions improve from west to east Friday morning. Showers redevelop Friday afternoon producing MVFR-IFR in rain/snow/graupel showers. Snow levels on Friday 3500-4500 feet. Surface winds: east-southeast 5-15 kts with gusts up to 25 kts overnight. Winds aloft at 10kft MSL: northwest 15- 25 kts. Weekend Outlook...Snow showers continue in the w-central Idaho mountains over the weekend producing local IFR conditions. VFR and drier at lower elevations. Westerly surface winds will become gusty Sat/Sun afternoon with northwest winds aloft. && .PREV DISCUSSION... SHORT TERM...Tonight through Saturday night...A wide swath of precipitation associated with a Pacific storm system is moving through western and central Oregon and will be headed for eastern Oregon by late this afternoon. Snow will develop first in Harney County this afternoon and spread into the remainder of southeast Oregon by early this evening. The snow will then move into southwest Idaho later this evening. The bulk of the snowfall is still on track to end by early Friday morning, but will persist in the higher elevations through mid-morning. A Winter Weather Advisory and Winter Storm Warning remain in effect for most of the area. Total snowfall amounts will generally range from 1 to 4 inches in the valleys and 4 to 8 inches in the mountains. A cold front will be accompanied by valley rain/snow showers and mountain snow showers as it moves across the area from northwest to southeast from Friday afternoon through Friday night. Additional light snowfall accumulations are expected. A weak upper trough moving through a northwest flow aloft will support snow showers in the higher elevations on Saturday. The showers may linger in the far northern high terrain Saturday night, otherwise drier conditions will develop within a northwest flow aloft. Temperatures will be generally 5 to 10 degrees below normal. Winds will be locally gusty tonight, and it will be windy in south-central Idaho on Saturday. LONG TERM...Sunday through Thursday...Moist northwest flow aloft will continue the chance for snow showers over the northern mountains on Sunday with below-normal temperatures. Moisture will be advected into the area on Monday to continue the precipitation over the northern mountains. Temperatures will increase to slightly above normal, allowing snow levels to rise to 4000-5000 ft MSL Monday afternoon. The next system will will dive south into the Pacific Northwest on Tuesday, ushering in much colder air and another round of high elevation snow. Wednesday afternoon will see a brief drying period ahead of an additional trough that will quickly dive across the region for another round of snow. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory until 11 AM MST Friday IDZ011-013. Winter Weather Advisory until 5 AM MST Friday IDZ014>016-030. Winter Storm Warning until 5 AM MST Friday IDZ012-029-033. OR...Winter Weather Advisory until 5 AM MST /4 AM PST/ Friday ORZ061>063. Winter Storm Warning until 5 AM MST /4 AM PST/ Friday ORZ064. && $$ www.weather.gov/Boise www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...KA AVIATION.....DG PREV SHORT TERM...BW PREV LONG TERM....AL