034 FXUS63 KBIS 242104 AFDBIS AREA FORECAST DISCUSSION National Weather Service Bismarck ND 304 PM CST Sat Dec 24 2022 .SHORT TERM...(This Evening through Sunday) Issued at 304 PM CST Sat Dec 24 2022 Light snowfall accumulations, strong winds, and the start of a warming trend highlight the short term forecast period. Western and central North Dakota is currently situated under northwest flow aloft and surface high pressure. Clouds across the west should continue to erode through the afternoon before increasing again tonight. We have one more bitterly cold night on tap, with actual lows ranging from the upper teens/lower 20s below zero east to the single digits below west. This will mean overnight wind chills in the 40 to 25 below zero range for all except for portions of the west. The Wind Chill Advisory remains in effect for all of these areas through Christmas Sunday morning. Precipitation chances increase overnight through Sunday, from northwest to southeast as an Alberta Clipper moves across the state. Strong upper level forcing will overspread strong low to mid level frontogensis and steep mid level lapse rates. All parameters appear to be in place for a mesoscale band of moderate to heavy snow to develop along the best frontogenetical signal, wherever that sets up. NBM consensus suggests the heaviest part of this band will setup from the north central, southeast through the greater Devil's Lake Basin, and into the James River Valley. While residence time should be relatively short under any one specific location (quick moving system), areas under the heaviest parts of the band could end up seeing 2 to 4 inches of accumulation with some locally higher amounts possible. Depending on how things evolve, instability from the lapse rates and very strong cold air advection could lead to some snow squall activity and it will be something we have to closely monitor. All that said, we decided to go ahead and issue a Winter Weather Advisory for snowfall accumulations of 2 to 4 inches and areas of blowing snow for Renville, Ward, Bottineau, McHenry, Sheridan, Kidder, Dickey, LaMoure, Rolette, Pierce, Wells, Foster, and Stutsman counties. This is the area we are most confident will see the greatest impacts and the advisory will be in effect from 06z Sunday through 06z Monday. West of the advisory, impactful winter weather is a bit more uncertain with lower snow totals and warmer temperatures. Soundings suggest much of the west and central could see a brief period of a wintry mix which could lead to a light glaze of ice accumulation. Very strong winds are also looking likely behind a cold front that will cross the state, especially across the southwest and south central with all guidance suggesting strong cold air advection, steep lapse rates, and strong pressure rises. Soundings suggest there could be 55 knots or greater of wind available to mix down at the top of the mixed layer for some locations. EFI values also confirm the potential for very strong winds here and were are advertising gusts up to 55 mph. Blowing snow could become a real problem southwest and south central, but temperatures could be the fly in the ointment. We will see significant warm air advection during the first part of the day across the southwest which will lead to highs in the lower 30s to upper 30s southwest and south central. This will make any snow on the ground much harder to loft. We will end up needing some sort of headline for this potential in the next shift or two, but uncertainty remains where that dividing line (if any) between just "wind" impacts and "winter" impacts will setup, complicating the forecast. For now, confidence is just not there to make that delineation. .LONG TERM...(Sunday Night through Saturday) Issued at 304 PM CST Sat Dec 24 2022 Some light snow may linger Sunday night but surface high pressure should settle in and push it out overnight and into Monday morning. On the backside of the Clipper, we could see another night on the colder side and one more night of a Wind Chill Advisory is possible across the east. While apparent temperatures will not be as bad as they have been recently, it still looks like widespread readings of 30 to 25 below are likely. Monday looks to be dry as upper ridging starts to push in. During the afternoon highs will rise into the mid 20s to mid 30s west and into the single digits to upper teens central and east. For the rest of the period, expect highs generally in the 20s and 30s with a chance for some lower 40s across the southwest. Another couple of weak waves will move through the region, bringing light precipitation chances back into the forecast Tuesday and Thursday. But given the low predictability of the pattern and model/ensemble disagreement, specifics are murky at this time. && .AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon) Issued at 1141 AM CST Sat Dec 24 2022 The first part of the period will see VFR conditions across the state, but the next Clipper will bring increasing chances of precipitation and lower ceilings from northwest to southeast tonight through Sunday. Precipitation will be snow for most but there is a potential for some light rain or freezing rain across the west towards the end of the period. Too much uncertainty still remains on location and potential for mention in site specific forecasts at this time. Ceilings will generally bottom out in MVFR categories, but brief IFR conditions are possible under any heavier snow pockets or in areas of blowing snow. There will also be enhanced low level wind shear overnight through Sunday morning. && .BIS WATCHES/WARNINGS/ADVISORIES... Wind Chill Advisory until 6 AM CST /5 AM MST/ Sunday for NDZ001>003-009>011-019>021-034-042-045. Winter Weather Advisory from midnight tonight to midnight CST Sunday night for NDZ003>005-011>013-022-023-025-036-037-048-051. Wind Chill Advisory until 9 AM CST Sunday for NDZ004-005-012-013- 022-023-025-035>037-046>048-050-051. && $$ SHORT TERM...ZH LONG TERM...ZH AVIATION...ZH