FXUS63 KDTX 202303 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 603 PM EST Mon Nov 20 2017 .AVIATION... The onset of nighttime cooling in the boundary layer is supporting decreasing sfc wind speeds. Low level south-southwest flow will however increase atop this shallow stable layer through the evening. 2k ft level winds are forecast to range from 50 to 60 knots through the night. This will remain supportive of low level wind shear into Tues morning, assuming there remains this shallow stable layer near the surface. A cold front will traverse Se Mi in the 15 to 22Z time frame on Tues. The front will be marked by a wind shift to the west. A region of MVFR and low end VFR clouds with a few rain showers will also accompany the front. For DTW...With a noted drop in sfc winds at 23Z, the timing of the low level wind shear will be moved up to 00Z. The onset of daytime mixing will transition the low level wind shear to mechanical wind shear mid to late Tues morning, meaning there will be an increase in the south-southwest sfc wind gusts. //DTW THRESHOLD PROBABILITIES... * Medium confidence in cigs aob 5000 feet after 18z Tuesday. * High confidence in precip type falling as rain tuesday afternoon. && .PREV DISCUSSION... Issued at 237 PM EST Mon Nov 20 2017 Discussion... Vigorous shortwave disturbance digging through the Canadian Prairie Provinces is inducing strong cyclogenesis south of Lake Winnipeg. This system will move east southeast to a position just north of Lake Superior by Tuesday morning. A strong cold front will sweep southeast through the northern plains and upper midwest in the wake of this wave, eventually tracking through southeast Michigan on Tuesday afternoon. Relatively mild conditions can be expected within well established southwest flow in advance of this front with temperatures pretty close to average for the third week of November (high temperatures in the mid to upper 40s and low temperatures tonight in the middle 30s. These conditions will hold into the middle of the day Tuesday before cold air advection steadies temperatures in the early part of the afternoon and then bring falling temperatures mid/late afternoon into the evening. While a large majority of the precipitation with this system will remain well north over portions of Ontario, models still signal a pretty decent, albeit brief, shot of rain showers along this front late Tuesday with some transition to a rain/snow mix or snow into the early evening before ending. However, surface temperatures will still be in mid/upper 30s with the last of the band of rain/snow so no accumulations are anticipated. High pressure will build into the area in the wake of this front from Tuesday night into Wednesday, leading to rather calm conditions after the region experiences southwest winds gusting to 25 to 30 mph late today and again into Tuesday afternoon. Notably colder readings can also be expected with high temperatures back into the middle 30s Wednesday and 20s for low temperatures both Wednesday and Thursday mornings. Surface high pressure will remain in control on Thursday before weak ridging downstream of the next approaching wave moves across the region on Friday. Low pressure tracking north of the region will then increase warm advection with 850 mb temps approaching 10 C allowing highs to make a run for 50 on Friday. The next chance for widespread rain will arrive Friday night as a cold front extending south from the low pushes through the region. Upper level troughing then digs into the Northeast US next weekend setting up a persistent northwest flow over the Great Lakes with 850 mb temps approaching - 15 C by Sunday. Cloudy, unsettled conditions look to dominate through the weekend as a series of weak disturbances pivot southeastward through the region. Saturday will be milder with highs in the low to mid 40s before a shot of colder air arriving on Sunday keeps highs in the low to mid 30s. MARINE... Southwest winds will continue to ramp up through this evening, and Gales still appear likely over the open waters of Lake Huron by Midnight, with 25 to 30 knots along nearshore waters, continuing into Tuesday before shifting to the northwest late in the day. Enough cold air advection and mixing expected to sustain Gale force winds over the north half of Lake Huron during Tuesday evening and the early morning hours of Wednesday. Scattered snow showers can also be expected over Lake Huron. High pressure building into the region will lead to dramatically decreasing winds for Wednesday, generally in the 10 to 15 knot range out of the west-northwest, with moderate southwest winds developing on Thursday behind the departing high. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Gale Warning until 4 AM EST Tuesday for LHZ462. Small Craft Advisory until 1 PM EST Wednesday for LHZ441. Small Craft Advisory until 4 PM EST Tuesday for LHZ442-443. Gale Warning from 10 AM to 10 PM EST Tuesday for LHZ361. Gale Warning until 10 AM EST Tuesday for LHZ363-421. Gale Warning until 4 AM EST Wednesday for LHZ362. Small Craft Advisory until 10 AM EST Tuesday for LHZ422. Lake St Clair...Small Craft Advisory until 4 PM EST Tuesday for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory until 4 PM EST Tuesday for LEZ444. && $$ AVIATION.....SC DISCUSSION...DG/JD MARINE.......SF You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.