421 FXUS65 KTFX 121137 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 438 AM MST Sun Jan 12 2020 ...Updated Aviation Discussion... .SYNOPSIS... An arctic front will move south from north-central Montana into central Montana today. Light snow will develop behind the front, with more widespread snow developing across the region this evening into Monday morning. Both temperatures and wind chills will drop to dangerous levels by tonight, and lasting through much of the week. && .DISCUSSION... This Morning through Monday...An arctic cold front continues to slowly push south across north-central Montana this morning, then will gradually work its way through the valleys of central Montana the next 12 to 24 hours, though models continue to back off on the extent of how far south it will make it into the central and southwest valleys. Many areas will likely see their high temperatures in morning across northern and central areas today. Snow intensity will favor focused upslope areas such as the Rocky Mountain Front and the mountains of southwest Montana, with much lighter overrunning snow across north-central Montana with generally one-half inch or less. A disturbance moving across the region from west to east will bring a quick round of accumulating snow, but this will be a progressive system with generally light snow amounts except in the favored upslope areas. Some breezy winds at times could also bring times of blowing snow. Dangerous cold begins to settle in through Monday along and behind the front, while near normal to slightly below normal temperatures continue to the south of the arctic front. The southwest however may see some increased breezes bringing cold wind chills and the potential for blowing snow. Monday night through next weekend...Some of the coldest air of the season so far is expected during this period, especially for the first half of the week. Overnight lows will fall to as low as 40- below and colder along the Hi-Line Tuesday and Wednesday mornings. The cold air will likely reach the southwest by late Monday into Tuesday, although current guidance is struggling with how fast it will move into this area, or in some cases if it even will make it all the way into SW MT. Highlights for wind chills below 20-below and/or light accumulating snow will be likely in the coming days as hypothermia and frostbite will increasingly become a real threat due to the dangerously cold temperatures along with periods of generally light snow. Chances for light snow look to continue into Tuesday, although timing and exact locations are still being determined. Of note, the trend continues in the models to moderate temperatures significantly back toward normal levels toward the weekend, though arctic air may be quite stubborn to move out over northeastern parts of north-central Montana. There could also be more rounds of light snow later in the week that will warrant keeping an eye on. && .AVIATION... Updated 438 AM MST Sun Jan 12 2020 (12Z TAF Period) Arctic cold front is at KGTF just before 12z this morning and continues to move south toward central MT. Behind the front, expect gusty northerly winds, increasing low clouds, and areas of light snow and/or haze. While MVFR/IFR/LIFR conditions are expected behind/north of the front, VFR conditions ahead/south of the front can be expected except at KWYS where MVFR/IFR/LIFR conditions will continue through the TAF period with -SN and BR. Mountains are expected to be obscured through most of the forecast period. && .HYDROLOGY... Ice jam flooding continues to impact low-lying areas along the River's Edge Trail between Riverside Park and around the Central Avenue Bridge. River levels continue to oscillate between 15 and 16 feet. Above 16 feet, river levels may cause flooding along River Drive at the train trestle. A Flood Watch is still in effect to account for potential impacts if river levels continue to rise. This will continue to be monitored and be sure to check the latest flood products and follow any local authorities' instructions in this area. && .PRELIMINARY POINT TEMPS/POPS... GTF 22 -6 3 -10 / 30 60 40 10 CTB 7 -16 -7 -20 / 30 70 40 20 HLN 31 7 20 3 / 20 60 40 10 BZN 33 15 27 13 / 20 40 50 10 WYS 20 8 19 6 / 60 80 70 60 DLN 28 13 23 12 / 10 30 20 10 HVR 15 -7 -1 -16 / 40 60 60 10 LWT 25 -3 6 -8 / 20 50 60 10 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 7 PM this evening to 8 AM MST Monday Beaverhead...Broadwater...Cascade...Central and Southern Lewis and Clark...Gallatin...Jefferson...Judith Basin... Madison...Meagher. Winter Weather Advisory until 11 AM MST Monday Blaine... Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton... Hill...Liberty...Toole. Winter Weather Advisory from 7 PM this evening to 11 AM MST Monday Fergus. Flood Watch through Monday afternoon Cascade. Winter Storm Warning until 5 PM MST Monday Northern Rocky Mountain Front...Southern Rocky Mountain Front. && $$ http://www.weather.gov/greatfalls