907 FXUS63 KMPX 271115 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 615 AM CDT Sun Mar 27 2022 .UPDATE... Issued at 612 AM CDT Sun Mar 27 2022 Updated for 12z aviation discussion. && .DISCUSSION...(Today through Saturday) Issued at 343 AM CDT Sun Mar 27 2022 - Critically low RH values Sunday and Monday afternoon. - Large storm system Tuesday-Thursday. Heavy rain, accumulating snow, and a wintry mix of freezing rain and sleet are all possible at times It's a chilly start to the morning with persistent north winds overnight allowing for temperatures to drop into the single digits across central Minnesota and into the teens elsewhere. Another bright and sunny day is expected, but temperatures will remain cold with high pressure centered overhead. Highs will only reach into the low to mid 30s. Despite the cold temperatures, very dry air under the high will allow for relative humidity values to drop into the teens across much of the area this afternoon. A few values in the single digits are possible across central Minnesota and west-central Wisconsin, which is more desert-like than Upper Midwest. Critical fire weather conditions will not be met despite the low RH values, as winds will be light with the center of the high overhead. Caution should still be used if doing any outdoor burning today. Another cool night is expected as winds remain light overnight with clear skies. Lows in the single digits are possible again across portions central Minnesota and west-central Wisconsin, with temepratures in the teens to low 20s elsewhere. Southeasterly winds pick up on Monday as the high pressure begins to depart to the east. Temperatures will be warmer as warm advection increases through the day; highs in the upper 30s to mid 40s are expected. Another day of critically low RH values looks likely as values could again drop into the teens, primarily north and east of I-94. Winds are expected to be lighter where the RH values are lowest, generally around 10-15 mph. Meanwhile wind gusts of 20-30 mph are likely to develop across western and southern Minnesota, but increasing moisture through the day means RH values will likely only drop to around 30%. There remains uncertainty on the evolution of the storm system moving out of the Rockies and into the plains on Wednesday. This will have major impacts on the associated surface features and precipitation amounts. Due to both a northern and southern jet stream and associated shortwaves embedded in these jets, global models are having trouble phasing these two together. Eventually, the embedded shortwaves will merge into one large storm system across the Great Lakes by Thursday. During the phasing period, models are trying to develop two areas of low pressure across the plains. First, and once the northern shortwave moves out of the northern Rockies, a surface low will develop with precipitation rapidly developing along and north of this feature. Initially, temperatures will be cold enough to warrant a concern of freezing rain across the north/northeast CWA (Mainly north of I-94 and east of I-35). NBM probabilities of receiving >0.01" of freezing rain is around 70-90 percent during the 24-hour time period from Tuesday evening through Wednesday evening for portions of west-central Wi, and east-central Mn. However, these probabilities diminish to less than 50 percent for anything more than 0.05". The greater potential of minor or moderate impacts of ice accumulation will occur across northern and eastern Wisconsin. The secondary shortwave moving out of the southern Rockies Tuesday will lead to another area of low pressure in the central/southern plains. This is where a line of severe storms will likely develop and will play a role on the northern surface low orientation and strength. Eventually, one storm system will develop somewhere across the Midwest/Great Lakes region Wednesday night. Due to differences in the global models and how the main surface low develops, confidence on where a band of measurable snowfall will develop once colder air arrives, is low. Consensus of the models and the overall mean suggest that eastern Mn/western Wi has the best probability of receiving a few inches of snow late Wednesday night, and into Thursday. Probabilities diminish farther to the west as the spread in the ensembles increase. The 500-hPa heights and anomalies from the global models suggest that the trend for the storm system is to limit the amount of precipitation across the Dakotas vs several model runs ago past Wednesday morning. For those concern on impacts of this storm system, please be aware of the uncertainties as this system is still hundredths of miles west of the west coast of the CONUS. Once this storm moves onshore and begins to interact with the Rockies and moisture from the Gulf of Mexico, will our region have a better idea of the strength, location and impacts of this developing system. && .AVIATION...(For the 12Z TAFS through 12Z Monday morning) Issued at 612 AM CDT Sun Mar 27 2022 VFR conditions through the period. Clear skies through today with mid-level clouds increasing overnight. Northerly winds of 5-10 kts through sunset, with winds becoming light and more easterly overnight. KMSP...No additional concerns. /OUTLOOK FOR KMSP/ MON PM...VFR. Wind SE 10-15 kts. TUE...AM VFR. MVFR/-RA likely PM. Wind SE 20G30 kts. WED...IFR/-RA likely with -SN possible late. Wind NE 10-15 kts bcmg NW 15G25 late. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...ETA/JLT AVIATION...ETA