Subj : North Plains Winter Storm To : All From : Dumas Walker Date : Fri Mar 22 2024 09:27 am FOUS11 KWBC 220807 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 407 AM EDT Fri Mar 22 2024 Valid 12Z Fri Mar 22 2024 - 12Z Mon Mar 25 2024 ....Northern Rockies & High Plains, Central Rockies, Upper Midwest... Days 2-3... **Significant late season winter storm becoming increasingly likely from the Northern Rockies and Northern High Plains to as far east as the Upper Midwest this weekend In wake of the storm system that tracked through the Upper Midwest Thursday night, the large dome of high pressure over the Canadian Prairies working in tandem with lower pressure in the West supports a prolonged low-level easterly easterly flow regime into the western Montana Rockies as well as central Montana and as far south as the Absaroka and Big Horns. Another 700mb FGEN band will strengthen throughout the day today and into Friday night as 700mb WAA increases over the northern High Plains. In addition, much of Montana lies beneath the divergent right-entrance region of a 100kt 250mb jet streak. This is a recipe for periods of snow today, however snowfall rates will not come down heavily enough during the day to do much more than Minor Impacts. Snow will accumulate more effectively Friday night. By Saturday morning, the approaching upper low in the Pacific Northwest will spawn a new surface low somewhere over eastern Idaho Saturday morning that will track into northern Wyoming Saturday evening. The surface low will continue its trek southeast into eastern Colorado, where NAEFS suggests it will eventually reach MSLP values that are <0.5 climatological percentile. Meanwhile, the 850mb LLJ will accelerate over the Great Plains with winds topping the 97.5 climatological percentile over the southern Great Plains around 06-12Z Sunday. The LLJ will advect anomalous 850-700mb moisture northward and wrap around the northern flank of the strengthening surface low, and give rise to a blossoming shield of heavy snow early Sunday morning from western Montana and northern Wyoming to the Dakotas. Strong 850-700mb WAA and copious amounts of Gulf of Mexico moisture will make its way into the Upper Midwest where heavy snow will then ensue over southern Minnesota. By 00Z Monday, a significant winter storm will be well underway, causing strong winds and heavy snow from the Central Rockies on east through the Black Hills, the Dakotas, and into the Upper Mississippi Valley. NAEFS by 00Z Monday shows MSLP values in parts of southwest Kansas and the TX/OK Panhandles that fall outside the observed MSLP minimum for this time of year (~980mb), showcasing the remarkable strength this storm will reach Sunday evening. By early Monday morning, the storm will track northeast towards the Missouri River with a pronounced TROWAL over the eastern Dakotas and western Minnesota being the focus for the heaviest snowfall. There remains some uncertainty in regards to the position and track of the storm, but most ensemble members are on board with this becoming an impressive late March winter storm. Latest WSSI-P shows moderate-to-high chances (50-80%) for Moderate Impacts from eastern Montana and along the ND/SD border to south-central Minnesota through early Monday morning. There are similar probabilities for Moderate Impacts that stretch as far south as the Sand Hills of northern Nebraska. There are even some low-to- moderate chances (30-50%) for Major impacts in parts of eastern South Dakota, southwest Minnesota, and throughout the Twin Cities metro area. The primary drivers in the WSSI-P algorithm are Snow Amount and Blowing Snow, the latter of which, shows >60% chances for Minor Impacts as far south as the Palmer Divide and into central Nebraska as a powerful cold front passes through these areas on Sunday. There are more details on the event in the Key Messages below, but residents in these areas are encouraged to closely monitor the latest forecasts this weekend as this storm will likely continue to cause hazardous impacts for parts of the Northern Plains and Upper Midwest into the start of next week. Mullinax ***Key Messages for Northern Plains Winter Storm*** --Significant winter storm likely Confidence continues to increase in a large storm system that will produce an area of heavy snow over the Northern Plains and into the Upper Midwest, along with some areas of mixed precipitation this weekend into early next week. --Widespread heavy snow expected Heavy snow is forecast to overspread eastern Montana late Saturday, then expand into the Northern Plains and Upper Midwest by Sunday afternoon. There is a high chance (>70%) of at least eight inches of snow from the North Dakota/South Dakota border eastward into Minnesota and northern Wisconsin. --Hazardous impacts due to snow, snow load, and wind A combination of heavy snow and gusty winds will likely produce areas of blowing and drifting snow, as well as possible blizzard conditions Sunday into Monday. Hazardous travel, along with some disruptions and closures are expected late Saturday into Monday. The combination of strong winds and heavy, wet snow on trees and power lines may result in tree damage and power outages. --Additional forecast changes anticipated Uncertainty remains with precipitation type for southern-most areas and a possible sharp northern snowfall gradient in northern-most areas. Closely monitor the latest forecasts as the storm evolved over the next 24-48 hours. $$ --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175) .