541 FXUS65 KBOI 191620 RRA AFDBOI Area Forecast Discussion National Weather Service Boise ID 920 AM MST Thu Dec 19 2019 .DISCUSSION...As of 9 AM MST snow was falling in the Idaho Lower Treasure Valley, Weiser River Basin, west central Idaho mountains, and southern part of the Boise Mountains. Snow was already falling in eastern Oregon. Burns showed about two inches overnight and this morning and roads were snow-covered. Worst conditions today are expected from the Lower Treasure Valley through the Upper Weiser Valley, and eastern Baker County/OR through Adams County/ID. Southern valleys will rise above freezing later today and roads will become wet. Steady or slowly rising temps tonight and warmer Friday as snow and rain decrease from sw to ne. No changes to current winter weather advisory. We may increase fog coverage tonight, and Friday night as well, in the afternoon package. Otherwise current forecast is on track. && .AVIATION...Mountain obscurations throughout the day. MVFR/IFR conditions within snow. Snow will continue to fall for elevations above 4k feet MSL throughout the day in our northern zones, mostly throughout central Idaho. Lower valleys will see snow mix with rain by mid-morning, then rain in the afternoon hours. Surface winds, southeast to southwest 5-10kts. Winds aloft to 10k feet MSL, westerly 35-45kts. Weekend Outlook... Patchy valley fog creating IFR/LIFR Friday morning. Becoming mainly VFR with mountain obscurations improving for Friday. Saturday, developing strong SW winds of 40-60 kts at 10Kft MSL, and breezy SE surface winds. Chance of snow showers and mountain obscurations return for Sunday. && .PREV DISCUSSION... SHORT TERM...Today through Friday night...Snowfall continues across the northern half of the forecast area this morning, with light snow starting to move into the Upper Treasure Valley. The significant moisture push will remain over the area with snow levels generally at or near valley floors through the afternoon. Numerical guidance continues to lower snow levels through the afternoon for the Treasure Valley. Have adjusted the prevailing snow and rain-snow mix areas accordingly. The heaviest snow accumulations are expected across the higher elevations of Baker County, and Lower Treasure Valley in Oregon, and the West Central Mountains and the Upper Weiser River area in Idaho. A Winter Weather Advisory remains in place for these areas through the evening hours. Additional details on intensity and timing can be seen in the product WSWBOI. Conditions are expected to improve across the area by Friday afternoon, with just a few lingering mountain snow showers through Friday evening. Warming temperatures expected through Friday. LONG TERM...Saturday through Thursday...The moisture plume responsible for the precedent precipitation will orient west of our forecast area through Saturday. The chance for precip will slowly return on Sunday, first over southeast Oregon, and then into southwest Idaho by late Sunday. Snow levels will start around 3000-4000 feet MSL, lowering to valley floors by Monday. The trough is forecast to exit the area Tuesday, allowing for a brief respite from showers. Thereafter, long-range models indicate the potential for more unsettled weather to return Wed/Thu. Temperatures will be milder over the weekend, but cooling to around normal for this time of year by Tuesday and beyond. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory until 11 PM MST this evening IDZ011-033. OR...Winter Weather Advisory until 10 PM PST this evening ORZ062. Winter Weather Advisory until 11 PM MST /10 PM PST/ this evening ORZ064. && $$ www.weather.gov/Boise www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...LC AVIATION.....JC PREV SHORT TERM...KB PREV LONG TERM....SH/DD