279 FXUS63 KDTX 120901 CCA AFDDTX Area Forecast Discussion...CORRECTED National Weather Service Detroit/Pontiac MI 401 AM EST Wed Feb 12 2020 .DISCUSSION... Today and Tonight: Wake of a departing high pressure system has left behind very dry air that extends throughout the atmospheric column, characterized by PW values around .15" with 1000-500 MB RH values holding on around 25 percent. This expansive column of dry air will ensure dry weather throughout the majority of the day across Michigan, while limited moisture flux will aid in returning temperatures back into the mid to upper 30s for a daytime high. Late Tonight to Thursday Morning: Attention will quickly turn to an open upper level wave currently located across the continental SW, specifically New Mexico/Texas and south into Mexico. This wave is expected to progress northeast and will become highly sheared as it lifts over the Ohio Valley later tonight. Surface low pressure in response to the passing wave will develop across the ArkLaTex region this afternoon and will quickly race across the Tennessee Valley, settling over eastern Ohio by 06Z, while a positive-tilt trough drops south across the Midwest. Track of this low pressure system will maximize moisture transport from the Gulf and will quickly overcome the copious amounts of dry air in the low to mid levels. Deep layer saturation and weak forcing from the sheared mid-level deformation will allow for accumulating snow to overspread across SE MI from south to north, after 00Z tonight. Deformation zone and aforementioned low pressure system have progressively trended weaker with latest model output and has resulted in a slight decrease in forecasted snowfall totals, with generally 2-3 inches for locations south of I-94 and 1-2 inches north. Elevated DGZ with surface temperatures just below freezing during snow event is also taken into consideration given any riming concerns, but an extra push from isentropic ascent between 03-06Z should help support several hours of snow rates on the order of .25" to .5"/hr closer to the Ohio border. Given the downward snow trends, will hold off on any winter headlines for this morning's forecast package. Late Thursday Morning to Friday Morning: Forcing mechanism for snow production to shift as rapidly approaching arctic front and a series of shortwaves tap into residual reservoir of moisture, producing on and off snow showers through the day. Arctic front is set to travel across SE MI from northwest to southeast from roughly 11Z-18Z and will produce highly variable snowfall totals by end of day. Stability parameters look to stay in check given the morning passage of the front, but strong uvv along the frontal slope will bring the chance to see embedded stronger snow showers. New accumulation totals will range between 1- 2 inches by end of day. Passage of the front will quickly drop temperatures down into the single digits by Friday morning with wind chills in the negative single digits, as a strong thermal trough arrives over the Great Lakes. Dry arctic air to end accumulating snow chances by early Friday morning. Friday Afternoon Onwards: h850 temperatures on the order of -20C will hold by Friday afternoon and will bring the coldest temperatures of the year, marked by daytime highs in the teens to lower 20s with wind chills holding in the single digits. Strong surface high pressure averaging 1034 mb will travel east from the Midwest into the Ohio Valley by Friday evening, producing dry conditions across Michigan. Return flow from the departing high will allow temperatures to rebound back into the 30s by Saturday and then will trend above normal for the early part of next week. Next chance for accumulating snow to come late Saturday into Sunday as an upper-level wave quickly travels across the state. && .MARINE... High pressure will continue its slide east into the Mid-Atlantic today maintaining southwest flow over Lake Huron. A low pressure system tracks northeastward through the Ohio Valley tonight bringing snow across the central Great Lakes region into Thursday. An arctic front drops south across the lakes during the day Thursday setting up a cold north-northwest flow with some freezing spray likely in Lake Huron. Strong high pressure will overspread the region Friday. && .PREV DISCUSSION... Issued at 1153 PM EST Tue Feb 11 2020 AVIATION... MVFR to lower VFR cigs will continue to lift north and exit terminals early in the forecast period as cirrus gradually thickens from south to north. The next round of accumulating snowfall still looks on track for the end of the forecast, working into I-94 area 00z-02z and points north a few hours later. Cigs will eventually drop to MVFR with this precip. For DTW...Any remaining MVFR stratus will clear at the beginning of the forecast. Accumulating snow then arrives 00z-02z Wed evening with a return of MVFR cigs late in the forecast. DTW THRESHOLD PROBABILITIES... * Low for cigs aob 5000 feet overnight...high by Wednesday evening. * High for precipitation type as snow Wednesday night. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ DISCUSSION...AM MARINE.......KDK AVIATION.....DG You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.