FXUS63 KBIS 231455 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 855 AM CST Sat Nov 23 2024 .KEY MESSAGES... - There is a chance (30 to 60 percent) of light accumulating snow this weekend across the north, with chances decreasing towards the south. Any snow accumulations are expected to remain below one inch. - Below average temperatures are expected this weekend and through next week. The coldest period is forecast over the Thanksgiving Holiday weekend. - While no major storms are forecast for next week, weather disturbances moving through the region will bring chances for light snow at times. && .UPDATE... Issued at 848 AM CST Sat Nov 23 2024 Patchy fog continues to linger across the southwest. This had lead to some light frost build up. Expanded and extended the patchy for the southwest to match current trends. Visibility reductions remain minimal with only a site or two dropping down to half a mile. Other than that no updates are needed at this time as the forecast remains on track. UPDATE Issued at 534 AM CST Sat Nov 23 2024 Mainly updated for Aviation Discussion (below). Did tweak sky cover to better match latest satellite imagery. All other weather elements on track this morning. && .DISCUSSION... Issued at 410 AM CST Sat Nov 23 2024 Currently, broad upper level ridge building east into the Great Plains, with another deep upper level trough developing over the west coast. Embedded impulse which brought some light accumulating snowfall earlier Fri evening and earlier this morning is tracking off to our east, with diminishing forcing across the local region as the upper ridge axis approaches and as a ridge of sfc high pressure builds southward into central ND. Resultant radar returns have indeed shown a downward trend in activity the past few hours. Upper ridge moves slowly east across the Northern Plains today, as a strong upper level jet rounds the base of the aforementioned upper trough and lifts east-northeast into the Northern Rockies. Embedded mid level energy ejecting out of the upper trough will organize as it interacts with left exit region jet dynamics, morphing into a closed low over far south central Canada Sat night into Sunday over the southern provinces of Saskatchewan and Manitoba. The projected track of the mid level low and its associated sfc trough will keep the bulk of QPF/accumulating snowfall north of the US/Canadian border, with NBM and WPC guidance continuing the downward trend in accumulations, now mostly less than one inch through Sunday across my north. CAA on Sunday on the back side of the sfc trough will see breezy northwest winds, with daytime highs Sunday trending cooler from today, then even colder for Monday with continued CAA, with forecast highs only in the teens and low 20s. Overnight lows Sun night will be in the single digits above, with wind chills in the single digits and teens below zero with a steady northwest breeze. Ridge of sfc high pressure settling over the state then looks to bring even colder overnight lows for Mon night/Tues AM, with lows in the single digits above and below zero, though with light winds. Ridge of high pressure building over the eastern Pacific and a long wave trough over eastern North America will then result in a dominate northwest flow aloft through next week and the Thanksgiving Holiday weekend. This pattern will maintain below average temperatures over the Dakotas, especially as we progress later in the week. Ensembles and NBM are still showing a couple of cold air surges, one around Thanksgiving Day and another over the weekend. NBM MaxT/MinT 25/75 percentile spreads have decreased, leading to higher confidence in the cold through Friday of next week (mean NBM MaxT values are 15-20 degrees below average for highs, with average highs for the local area in late Nov right around 30F). Multiple shortwaves will also move through the region next week, each bringing the chance for some light snow and a period of elevated winds as associated frontal boundaries push through. With sub-zero temperatures forecast during the nighttime/morning hours late in the week, will need to keep an eye on wind chill temperatures, as they are currently projected to range from 10 below to 30 below zero Thursday, Friday, and Saturday mornings. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 534 AM CST Sat Nov 23 2024 Widespread MVFR with localized IFR ceilings continue through much of western and central North Dakota, though many parts of north central North Dakota including the KMOT terminal remain VFR. Ceilings over most locations will slowly improve a bit this morning/afternoon, but will again lower later in the afternoon/evening as the next weather disturbance moves into the area, which will also bring snow to northern locations reducing visibility. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Johnson DISCUSSION...NH AVIATION...NH