875 FXUS63 KDTX 161001 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 601 AM EDT Sun Oct 16 2022 .AVIATION... Inbound cold front is on the doorstep of MBS at press time, with NW flow over northern lower MI already touching off lake enhanced stratocu. Pace of the front is generally on par with inherited TAFs for metro terminals, although have sped up timing a bit from MBS to PTK given current propagation. Models have trended toward a slightly drier boundary layer while upstream observations flirt between MVFR and low VFR, thus could see a few intervals of MVFR for MBS/FNT/PTK in the WNW flow regime mid/late morning, but confidence is low in the stratus deck holding together. As boundary layer growth ramps up, low level moisture flux should equate to ceilings settling around 5000 feet this afternoon and stay there through the early evening. More unsettled period arrives after 00z with a boost from the approaching upper low, with showers increasing in coverage and ceilings lowering accordingly. Mid-level dry air atop a deep layer of low level moisture results in MVFR ceilings developing late Sunday night which persist through the end of the TAF period. DTW THRESHOLD PROBABILITIES... * Moderate for ceiling 5000 feet or less mid morning to mid afernoon today and then again tonight. && .PREV DISCUSSION... Issued at 308 AM EDT Sun Oct 16 2022 DISCUSSION... A lead mid level positive PV anomaly along the nose of a northern stream jet max will dive into the Minnesota arrowhead this afternoon and into Wisconsin this evening. This will result in amplification of the longer wave trough over the Great Lakes while the deep layer meridional flow transports an airmass originating from the Canadian Arctic into the Great Lakes region over the next couple of days. The amplification of the long wave trough will evolve into a closed upper low in the vicinity of Lake Huron on Monday. This upper low will reside over the region into Wednesday before it gradually rotates northward toward James Bay by Thursday. The airmass that will be driven into the Great Lakes will be quite cold for mid October. 850mb temps are forecast to be in the negative teens upstream of the lakes. While there will be a good deal of modification off the relatively warm waters of the Great Lakes, 850mb temps will still plunge into the negative single digits over Se Mi on Monday and linger over the area through at least mid week, supporting well below normal temperatures. Short wave impulses rotating around the upper low, moisture flux off the Great Lakes and a resident cold pool aloft will support periodic showers across the forecast area through the first half of the week. There has been some low level warm air advection overnight within low level southwest flow. The wind fields will veer toward the west this morning, leading to weak low level cold air advection during the course of the day. This will be offset to a degree by diurnal heating, particularly across the south with some early day sunshine. The approaching mid level wave will result in respectable height falls across the are during the latter half of the day. Despite limited moisture, increasing over lake instability under westerly flow and a gradual deepening of the convective cloud depths will support increasing shower chances late today into tonight. As the upper low develops late tonight/Monday, deep layer moisture will progress into Se Mi from the north. The mid level cold pool (with 500mb temps down to -34C) will also expand across Se Mi from the north, leading to mid level lapse of rates of up to 8.5 C/kg. In fact, by Monday afternoon, model soundings show steep lapse rates from the sfc all they way to 450MB. Diurnal enhancement along with lake effect under west-northwest flow will produce occasional showers, with the instability component suggestive of some graupel and even thunder in some of the heavier convective elements. Although there is still some model spread at this stage in the forecast, model solutions suggest a stronger short wave impulse rotating across Se Mi either Mon night or Tues morning, which will likely enhance shower coverage. With cooling boundary layer temps, wet bulb zero heights dropping below 1000 ft, some wet snow will be a possibility Mon night/Tues morning. Cold and blustery conditions with periodic showers will continue into Wednesday. While the upper low is forecast to lift into James Bay by Thursday, GFS/ECMWF/Canadian all indicate a fast moving northern stream short wave advancing across Lower Mi Wed night/Thurs, offering some reinforcement to the cold air. Mid level heights will then rebound by Friday with strengthening southwest flow supporting a rapid warming trend to end the forecast period. MARINE... An upper-level low will remain in place over the Great Lakes into early next week ensuring that cold air remains firmly entrenched across the local waters. Moderate west southwesterly flow will prevail today with gusts generally peaking around 20 knots across much of the local waters, except up to 25 knots at times across portions of the central Lake Huron basin. Initially dry conditions will give way to increasing chances for showers as low pressure begins to develop in vicinity of Georgian Bay. Developing surface low pressure near Georgian Bay Monday into Tuesday, in addition to additional upper-level energy diving out of the northern Great Lakes, will bring a return of unsettled weather to the local waters, with scattered to numerous showers and the potential for waterspouts across the Lake Huron basin. Winds around the surface low will veer further to the northwest Monday night into Tuesday with gusts potentially reaching gale-force in strength, and this period will continue to be monitored for a potential Gale Watch. Higher pressure will then finally begin slowly building into the Great Lakes from the Midwest for the remainder of the week as the upper-level low breaks down and lifts into Quebec. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....MV DISCUSSION...SC MARINE.......IRL You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.