620 FXUS65 KTFX 091209 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 509 AM MST Thu Mar 9 2017 .DISCUSSION... Today through Friday...A weak shortwave trough in the moist west- northwest flow aloft will cause the light to moderate snow across much of the area to decrease today. However, another surge of Pacific moisture will move into the area tonight and continue through Friday, bringing another round of moderate to heavy snow at times. The mountains along the Continental Divide from the Canadian border south to near MacDonald Pass will receive the most additional snow through Friday, with another foot or two possible. Lower elevations across the remainder of North Central and Central Montana should get another 2 to 6 inches due to lingering northerly upslope winds behind a Canadian cold front, with mountains there receiving 6 to 11 inches. The front will likely remain between Helena and Bozeman through tonight, before it starts to move north on Friday. As a result, the southwest valleys will remain above freezing, limiting the potential for any snow. However, above 6500 feet, light accumulating snow can be expected. An additional 2 to 4 inches is possible on mountain passes and in West Yellowstone, with another 6 to 11 inches possible in the mountains. Highs in the teens are likely today north of the front, with mostly 30s to the south of it. Single digit lows are likely in the north, with 20s in the south. As warmer air creeps north on Friday, there will be a slight chance of freezing drizzle mixed with the snow across the north before below freezing temperatures begin to warm there behind the front as it moves north as a warm front. Coulston Friday night through Sunday...During this period, a surface front is still expected to remain nearly-stationary along the Rocky Mountain Front and Central MT mountains as a strong surface high pressure ridge persists over the Canadian Prairies and Great Plains of MT. Periods of snow, especially over North-Central MT, should taper-off Friday evening into Saturday morning as a shortwave trough exits to the east and a stabilizing shortwave ridge builds-in from the west. After a quiet Saturday afternoon, more periods of snow are possible Saturday evening into Sunday morning, mainly for North-Central MT, as another shortwave trough moves eastward across the CWA and interacts with the aforementioned surface front, resulting in moist isentropic lift. North of the surface front, temperatures will be below normal across much of North-Central MT, while temperatures in much of Southwest MT will be near or slightly above normal. Sunday Night through Thursday...Another round of precipitation, primarily in the form of snow, should occur over North-Central MT Sunday night into Monday as a low- to midlevel shortwave trough moves-in from the Pac NW and interacts with the nearly-stationary surface front. During the day on Monday, this surface front should move northeastward as a warm front. This should occur due to surface pressure falls and WAA ahead of the aforementioned shortwave allowing the persistent surface high pressure ridge over the MT Great Plains to finally slide eastward. Thereafter, a high pressure ridge aloft should build eastward into our CWA for Tuesday through Thursday. However, scattered mountain snow showers and lower- elevation rain/snow showers remain possible as multiple eastward- moving weather disturbances may traverse the ridge. A moderating trend should allow temperatures to tend near or above normal during the period. Jaszka && .AVIATION... UPDATED 0600Z. Periods of snow to bring MVFR to IFR conditions throughout the forecast period. Snow is starting to develop along and north of a line from KHLN to KGTF to KLWT. This will be the main focus for snow tonight through Thursday morning...although sites across the south may also see periods of snow at times. MVFR to IFR conditions are expected with any prevailing snow. Snow may then diminish slightly Thursday afternoon...however...MVFR conditions are still possible for any site with lingering light snow. The next round of snow will then move from south to north Thursday evening...bringing more widespread MVFR to IFR conditions to most sites. Expect the mountains to be obscured throughout much of the forecast period. Anglin && .PRELIMINARY POINT TEMPS/POPS... GTF 16 12 33 13 / 100 100 80 20 CTB 8 3 18 1 / 60 100 80 30 HLN 28 20 45 25 / 100 100 70 10 BZN 37 26 47 26 / 70 90 80 10 WEY 36 30 39 21 / 80 90 90 20 DLN 46 35 51 29 / 40 50 50 10 HVR 17 7 17 3 / 50 90 100 40 LWT 17 9 30 10 / 100 100 90 20 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 8 PM MST Friday Broadwater... Cascade...Chouteau...Eastern Pondera...Eastern Teton...Fergus... Jefferson...Judith Basin...Meagher. Winter Storm Warning until 8 PM MST Friday above 4500 feet for Central and Southern Lewis and Clark...Northern Rocky Mountain Front...Southern Rocky Mountain Front. Winter Weather Advisory from 5 PM this afternoon to 8 PM MST Friday Blaine...Eastern Glacier...Hill...Liberty...Toole. Winter Weather Advisory until 8 PM MST Friday above 6500 feet for Beaverhead...Gallatin...Madison. Winter Weather Advisory until 8 PM MST Friday below 4500 feet for Central and Southern Lewis and Clark...Northern Rocky Mountain Front...Southern Rocky Mountain Front. && $$ weather.gov/greatfalls