725 FXUS63 KDTX 130405 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1205 AM EDT Fri Mar 13 2020 .AVIATION... The latest observations leading up to press time indicate the cold front moving through central and SE Lower Michigan. Rain showers are mainly focused in a band along the frontal zone and bring just an hour or two of MVFR visibility and possibly IFR ceiling. After that, the main concern is west wind increasing to gusts around 30 knots during the morning and then lasting through afternoon. MVFR ceiling also lingers behind the wind shift until mixing into broken low end VFR. Cloud coverage becomes more scattered south of FNT heading into the mid afternoon and evening. For DTW... MVFR ceiling returns with passage of a cold front during the night. These clouds linger through morning while west wind increases to 30 knot gusts after sunrise. The gusty conditions last through the day while clouds lift and scatter by afternoon. Wind direction remains from about 280 likely exceeding crosswind threshold until diminishing Friday evening. .DTW THRESHOLD PROBABILITIES... * High for ceiling 5000 ft or less late tonight through morning. Low this afternoon. * Moderate to high for westerly wind gusts exceeding crosswind threshold late tonight into Friday evening. && .PREV DISCUSSION... Issued at 1010 PM EDT Thu Mar 12 2020 UPDATE... The forecast is on track for scattered showers preceding the cold front, along with a band of showers along the front itself, before the system sweeps eastward prior to sunrise. After that, colder air surges into the region on west wind gusting in the 30-40 mph range that lasts through Friday. Observations leading into mid evening indicate low pressure deepening over central Lake Superior with a band of showers extending southward into northern Illinois. From there into central Indiana, surface analyses indicate secondary low pressure that could have some MCV-type origin but no better than a hybrid. This portion of the system is due the surface low being connected to a coherent low level thermal and moisture structure within the primary warm front across the Ohio valley. The larger scale upper level trough sweeps in from the Midwest and generates some isentropic ascent and moisture transport from this frontal zone northward into Lower Michigan prior to the cold front. This process is responsible for at least scattered coverage of rain showers developing from the Ohio border to the northern Detroit suburbs and Port Huron. The band of showers along the cold front then sweeps through and affects the area more from Flint into the Tri Cities and northern Thumb. Deepening of the primary surface low over northern Ontario coupled with strong isentropic descent/mid level subsidence and low level cold advection force ramped up west wind mainly after 4 AM. Peak gusts are expected to reach the 30 to 40 mph range as boundary layer mixing develops late morning into early Friday afternoon. PREV DISCUSSION... Issued at 308 PM EDT Thu Mar 12 2020 DISCUSSION... Upper level trough tracking through upper Mississippi River Valley this afternoon, with cold front looking to come through southeast Michigan around midnight. Low clouds through the day have subdued/slowed the warmup, but temps should still rise into the low to mid 50s early this evening. Question remains whether there will be enough moisture to support widespread showers with the good but brief FGEN that works through tonight, as the best lift resides over northern Lower Michigan. Meanwhile, Deep Pacific moisture surging through the lower/central Mississippi River Valley, with convection developing over southern Ohio Valley, which will tend to rob the moisture transport into the Lower Michigan, and confidence for a solid line of showers is just not there tonight, as southeast Michigan could easily be caught in between the two systems. In any event, will still hold onto likely pops, albeit the duration of the rain showers is expected to be brief and light. Much higher confidence in the windy conditions setting up tomorrow as cold pool (-10 C at 850 MB)/trough axis/mature dry slot arrives in the morning hours. Deep boundary layer mixing will tap into the 40 knots, and expecting to see wind gusts of 35-40 MPH at the surface, also supported by local probabilistic guidance. 850 MB temps of -6 to -7.5 C by the end of the day suggests highs in the low to mid 40s. Upper level northwest confluent flow Friday night allows strong surface ridge to build into the Central Great Lakes through the weekend, as the center of the high builds 1046-1050 mb over Ontario. Favorable radiating conditions with the dry airmass suggests temps falling into the 20s with teens not of the question, barring clouds. Will be contending with some mid/high clouds Friday night (especially toward the Ohio border) as system tracks just south of the Ohio River on Saturday. Otherwise, some lake stratus could be an issue Saturday night as winds shift to the northeast off Lake Huron. Pronounced surface ridge looks to hold on at least into Monday, maintaining a dry forecast. A weak northern stream trough is progged to track through the northern Great Lakes on Tuesday, but the cold front is weak and ill defined, and looks like just a slight chance of pops. Per 12z euro, ridging at surface and aloft returns for Tuesday night into Wednesday, but an active warm front looks to be lifting into the state toward evening. MARINE... Low pressure developing over Lake Superior today becomes the primary driver of unsettled marine conditions to finish the week. A general light to moderate south wind develops ahead of the system over the central Great Lakes bringing milder air into the region. This means a pattern of rain as precipitation moves in this evening and tonight. The low pressure system then deepens considerably over northern Ontario tonight and Friday while pulling a strong cold front across Lower Michigan and Lake Huron. Colder air surging in over marine areas builds the mixed layer and taps into a stronger wind field aloft supporting westerly gales across northern Lake Huron from late tonight through late Friday night with Small Craft Advisories for the remaining nearshore marine areas. Some brief periods of gale force gusts are possible over central/southern Lake Huron as well as over the nearshore zones around the Thumb and Saginaw Bay. These gusts are not expected for an extended period of time so a gale warning has not been issued for those areas. The low pressure system weakens over northern Quebec to start the weekend which allows a diminishing marine wind trend during Saturday. High pressure takes control by Saturday night and holds through Sunday into Monday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Advisory from 3 AM Friday to 3 AM EDT Saturday for MIZ049-054. Lake Huron...Small Craft Advisory from 3 AM Friday to 3 AM EDT Saturday for LHZ421-422-441>443. Gale Warning from 3 AM Friday to 3 AM EDT Saturday for LHZ361-362. Lake St Clair...Small Craft Advisory from 3 AM to 5 PM EDT Friday for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory from 3 AM to 5 PM EDT Friday for LEZ444. && $$ AVIATION.....BT UPDATE.......BT DISCUSSION...SF MARINE.......KK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.