FXUS63 KDTX 111025 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 525 AM EST Mon Dec 11 2023 .AVIATION... Cold light northwest-west flow this morning should maintain low clouds (2500-3500 feet) across southeast Michigan. Warming and drying out of the 850 MB level this afternoon offers up some potential for clearing skies, but likely going to be sufficient moisture around 3000 FEET to maintain borderline MVFR/VFR clouds into the evening hours. As winds shift to the southwest this evening and further warm advection takes place, more defined clearing should take place from south to north tonight. For DTW...Don't see cloud bases deviating much from 3000 feet today, with any partial clearing this afternoon likely refilling back in for the evening hours. Uncertainty with the exact time of clearing tonight. .DTW THRESHOLD PROBABILITIES... * High for ceiling aob 5000 feet this morning, then lowering confidence to low by this evening. && .PREV DISCUSSION... Issued at 303 AM EST Mon Dec 11 2023 DISCUSSION... Deep layer subsidence amid building heights in the wake of a departing mid level wave will expand across Lower Mi this morning and prissiest into tonight. This large scale subsidence will deepen the low level inversion, which will likely hold the stratus deck in place into the evening. This and limited low level thermal advection will keep daytime temps mainly in the 30s today. Low level wind fields will back toward the southwest tonight and will strengthen. This will drive a warmer low level airmass into Se Mi, eroding the low level inversion and allowing for a clearing trend. Despite the clearing trend, the strength of the gradient flow (1500- 3k ft level winds of 40-45 knots) will limit nocturnal cooling and support nighttime lows mainly in the upper 20s. The backed flow will be in advance of a cold front moving into the northern lakes tonight. Models have trended a bit stronger with the amplitude of the mid level trough within the base of a polar low originating from central Canada and moving into northern Ontario by Tues morning. This will force the associated surface front all the way into the Ohio Valley by Tues evening. The larger scale dynamics will be focused north of the forecast area. Model cross sections actually indicate the frontal forcing becoming very shallow as it pushes across Se Mi, even falling apart by the time it pushes south of metro Detroit. Model solutions also show a fairly significant mid level dry layer advecting into srn Lower Mi by afternoon. While there will likely be some low clouds with fropa, a dry forecast will continue to be warranted on Tuesday. The low level wind fields along the front will still support fairly breezy conditions. The strongest wind fields are actually expected within the prefrontal airmass as opposed to the post frontal cold air advection region. With the support of model soundings and probabilistic guidance, peak wind gusts will be kept to 30 MPH, perhaps a little higher in the northern thumb. The cold front will usher in a seasonally cold airmass for the midweek period. Broad sfc high pressure will expand and strengthen across much of the eastern US during the latter half of the week within a split mid level flow regime across the CONUS. Most notable will be the warm air advection within the return flow of this sfc high which will bring mild air to the forecast area by the end of the week. MARINE... There will be a backing of the winds during the course of the day and evening ahead of a cold front approaching from the northwest, forecast to move into far northern Lake Huron Tuesday morning. Prefrontal southwest winds will become quite strong across Lake Huron tonight and into Tuesday morning. The potential for gales will hinge on the degree of mixing to the lake surface as these winds will drive a warmer low level airmass across the lake. There does look to be a potential for a period when there is enough over lake instability to cause some southwest gale force gusts across Saginaw Bay into central Lake Huron. Current probability guidance is under 50 percent for gusts to gales, however there has been an increase in the probabilities the last few model cycles. Therefore, a gale watch will be issued for Saginaw Bay and central Lake Huron overnight into Tuesday morning. Later forecast shifts will determine if an upgrade to a warning is needed. THe post frontal wind fields will not be as strong. There does look to be a period Tuesday afternoon into Tuesday night where the gradient increases across the north third of Lake Huron. While there is a potential for a few brief gusts to gale force, guidance is more supportive of 30 knot type wind gusts attm. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Gale Watch from late tonight through Tuesday afternoon for LHZ363- 421-422-441-462. Small Craft Advisory until noon EST today for LHZ441. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....SF DISCUSSION...SC MARINE.......SC You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.