FXUS65 KBOI 051711 AFDBOI Area Forecast Discussion National Weather Service Boise ID 1011 AM MST Tue Mar 5 2024 .DISCUSSION...Widespread snow (locally moderate-heavy) will continue along a west-east oriented front the extends from near Burns to Fairfield. The front and associated snow is expected to move slowly southward this afternoon and evening. There is a 30-40 percent chance that the snow mixes with rain in the lower valleys this afternoon which would limit additional snowfall amounts. Latest temperatures in the valleys have been above 32F in the lower valleys and the trend is for a slight increase in temps this afternoon resulting in either wet or slushy roads. There is a 30-50 percent chance of exceeding 4 inches of snowfall in Boise and surrounding metro areas, but additional snowfall will mainly accumulate on grassy areas. Winter Storm Warnings and advisories are in effect for most of the area through this evening. Gusty winds to 50 mph are expected near the ID/NV border through this afternoon where a Wind Advisory is in effect. No updates for now. && .AVIATION...Widespread MVFR/IFR and local LIFR in light/moderate snow. Snow will continue in a broad, west-east band focused north of the KMUO/KREO line. Lower elevations below 4000 ft MSL should transition to rain or rain/snow mix after Tue./19z, then become all snow again Tuesday evening as the west-east precip band moves southward toward the NV border. Snow will be mostly south of the KMUO/KREO line after Wed./06z. Mountains obscured. Surface winds: SW to SE 10-20 kt. Gusts to 25 kt beginning early Tues morning, except 30-40 kt gusts south of KBNO and Snake Plain. Winds aloft at 10k ft MSL: SW-W 25-45 kt shifting W 10-25kt after Wed./18Z. && .PREV DISCUSSION... SHORT TERM...Today through Thursday night...Ongoing winter storm will continue through late this evening. Precipitation will be mostly snow with a change to rain and snow in the valleys this afternoon. Shadowing has limited precipitation in parts of the Treasure Valley (Boise through Mountain Home) thus far (as of 03z) but do expect the precipitation to overcoming the shadowing by sunrise. The frontal boundary should help this later this morning but it's placement varies quite a bit in the high-res models. The consensus seem to place the boundary from Burns-Ontario-Banner Summit. Surface temperatures will remain at or above freezing through the early this evening which limit snow accumulation to cold surfaces. Overall, snow amounts will vary quite a bit in the Treasure Valley, with the highest amounts (about a 60% chance of 2" or more) between Ontario and Nampa through noon today. Snow is possible for the Boise Metro this morning however, less snow is expected with about 30% of 2" or more through noon today. Max temperatures today are forecast between 37 and 43 degrees in the valley which suggests that snow will mix with rain this afternoon. This will limit additional snow accumulations to cold ground surfaces keeping roads wet. The front will shift southward early this evening. This will bring cold air from the north allowing for snow at all elevations. This could become more problematic for the Treasure Valley as 1-3" of additional snow will likely freeze on all surfaces with temperatures falling into the upper 20s. The front weakens as it shifts southward which will limit snowfall for the Eastern Treasure Valley and Western Magic Valley Wednesday morning. West Central and Boise Mountains along with the Camas Prairie will see significant snowfall of 4" to 8" in the mountain valleys and 10" to 16" above 7000 Feet today. Overall, current headlines look good for this event so no changes needed at this time. Cold northerly flow and fresh snow cover will keep temperatures below normal for Wednesday but will begin to warm as an upper level ridge moves over the area on Thursday. Much of the snow will melt off in the valley Wednesday. LONG TERM...Friday through Tuesday...Friday through Saturday evening is dry and mostly clear with a slight warming trend as an upper ridge builds. Saturday evening an upper trough moves inland rather quickly, but seems to weaken as it does so. Precipitation chances are 20-40%, highest over terrain and in the northern half of our area. Based on the arrival time of the moisture and snow levels of 3000-4000 ft MSL, lower valleys are favoring rain or a very wet snow. Either way, the amount of precipitation that falls with this trough will be very light. Precipitation ends Sunday morning, and southwest flow aloft continues to warm us and raise snow levels before the next trough moves in on Monday. This systems appears overall much wetter than Saturday night's, but there is some uncertainty in the timing as some models show precipitation beginning in the morning and some in the evening. Snow levels of 4500-5500 ft MSL make valley snow unlikely, even overnight. Breezy conditions will accompany both troughs in the long term. Temperatures will be around 10 degrees below normal through Friday, warming to within 5 degrees of normal over the weekend and into next week. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory until 11 PM MST this evening IDZ011>014-033. Wind Advisory until 5 PM MST this afternoon IDZ015-030. Winter Storm Warning until 11 PM MST this evening IDZ028-029. OR...Winter Weather Advisory until 11 PM MST /10 PM PST/ this evening ORZ063-064. Winter Storm Warning until 10 PM PST this evening ORZ061. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...BW AVIATION.....SA SHORT TERM...JDS LONG TERM....JM