420 FXUS65 KBYZ 061101 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 401 AM MST Sat Feb 6 2021 .DISCUSSION... Today through Sunday night... Widespread severe winter weather will keep going this weekend. The Winter Storm Warnings and Winter Weather Advisories remain in place, except for Custer and Fallon Counties where the Winter Weather Advisory has been replaced by a Wind Chill Advisory. Surface high pressure over Alberta and Saskatchewan will continue to feed Arctic air into our region this weekend. At the same time, moist air aloft has been and will continue to flow east/southeastward over the cold air, rise, and produce snowfall over our area. The snow has lightened a bit over south central MT and north central WY early this morning, and has stopped in southeast MT, as some drier air has made a brief appearance over northeast MT as a shortwave trough moves southeastward into the Dakotas. That shortwave trough and drier air will move farther away from the region this afternoon, and another surge of colder air will move southwestward into the region. This evolution combined with an area of greater mid-level moisture moving in from the west/northwest and mid-level dynamics should encourage an overall increase in the snowfall this afternoon into Sunday morning, with light snow extending to southeast MT, and moderate to locally heavy snow occurring over south central MT and north central WY. Additional snow accumulations through Sunday are expected to range from around 1 inch over east-central MT near Baker to about 3 to 5 inches over the lower elevations of Sheridan County, WY and 4 to 9 inches over south central MT. Snow will then lighten Sunday night as some drier air moves over the region. Temperatures today will rise slowly to the single digits and teens above zero, drop to the single digits digits above and below zero tonight, rise to the single digits above zero Sunday, then drop to the single digits and teens below zero Sunday night. Wind chill values will be below zero at least periodically this weekend, with the coldest wind chills expected Sunday night. Dress warmly to avoid frostbite. RMS Monday through Friday... Forecast remains cold for the first half of the week, and is trending colder for the second half. This means single digit above/below zero high temperatures are now being advertised through Friday for all areas, and probabilities of sub zero highs on Saturday range from 20 to 40 percent for all but the western foothills. Overnight lows are expected to be in the teens below zero, with some areas possibly falling below -20. The coldest nights look like Tuesday and Wednesday night, with early morning wind chill values of -30 to -40 degrees. Light snow will continue Monday and Tuesday, with accumulations of less than an inch each day. Given the continued cold air light snow may continue through the week. Models starting to advertise some QG forcing for Thursday and Friday that may necessitate higher precipitation chances during those periods. There are also hints at an upper low sliding in off the central Pacific and into Idaho and Wyoming over the weekend that could be an interesting system if it arrives as currently advertised. Bottom line, winter will persist through the foreseeable future. Chambers && .AVIATION... A long lasting winter storm will bring IFR or lower conditions through the weekend across the region, including all taf sites. While there may be brief periods of improvement (mainly over SE Montana), there is no lasting improvement expected through Monday. Chambers && .PRELIMINARY POINT TEMP/POPS... Tdy Sun Mon Tue Wed Thu Fri ------------------------------------------------------- BIL 011 902/003 912/000 915/904 915/904 914/901 916/002 +/S +7/S 35/S 32/S 10/I 11/I 11/B LVM 018 004/010 906/008 910/009 909/003 914/003 914/005 8/S 97/S 44/S 32/S 10/B 11/B 11/B HDN 011 902/004 911/002 915/902 916/902 915/901 919/001 9/S +7/S 35/S 32/S 00/I 11/I 11/B MLS 007 907/002 913/001 917/901 917/903 916/902 919/000 3/S 86/S 12/S 11/I 00/I 00/I 10/B 4BQ 009 901/007 913/003 916/000 914/901 916/902 920/901 3/S 96/S 23/S 21/B 00/I 00/I 10/I BHK 003 910/002 914/001 916/001 916/903 917/903 919/000 1/B 66/S 11/E 11/U 00/I 00/I 10/B SHR 017 001/007 909/005 913/005 913/001 915/901 918/003 7/S 97/S 33/S 32/S 00/E 11/I 11/B && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...Winter Storm Warning in effect until 5 PM MST Sunday FOR ZONES 29-34-40-42-56>58-63>68-138-139-141-169>173-228-235. Winter Weather Advisory in effect until 5 PM MST Sunday FOR ZONES 30-31-36-37. Wind Chill Advisory in effect until 5 PM MST Sunday FOR ZONES 32-33. WY...Winter Storm Warning in effect until 5 PM MST Sunday FOR ZONES 198-199. && $$ weather.gov/billings