982 FXUS63 KDTX 130830 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 430 AM EDT Mon Apr 13 2020 .DISCUSSION... Latest MSAS analysis this morning highlights the dueling 994mb surface low pressure centers, one over portions of Ohio, the other lifting northward over the far northern Lower Michigan. Locally, Southeast Michigan is sandwiched within a broader radius surface low that remarkably extends from the Straits southward into Tennessee. The northern mslp low center will become the dominant feature moving forward today as the the RAP based 6Z mesoanalysis shows the harbinger H85 height minimum of 1296m centered around the Leelanau peninsula. Observations at this early hour largely supports earlier metoerological reasoning provided within the past 24 hours. A few areas of organized precipitation are occurring over the western and central Great Lakes, one is along the 925-850mb quasi- stationary frontal zone along western shore of Lake Michigan, the other is more subtle and appears tied to a mesoscale corridor of higher theta e content/convergence tied with the surface low center along the eastern Lake Michigan shoreline. For Southeast Michigan specifically, regional mosaic earlier showed general subsidence lifting northward into the cwa. This subsidence has proven rather formidable with a lack of any organized precipitation clear down through central IN and central OH. Survey of modeled vertical moisture does show mid to upper level dry air/a dry slot from 650- 400 mb. Moving forward, will be relying on lower tropospheric processes for light precipitation/drizzle as lowest 7.5 kft agl remain saturated prior to the cold front. Given nil warm sector moisture transport the support for any moderate to heavy rainfall has ended. No thunderstorms are anticipated this morning. The main weather concern remains the strong westerly winds that will develop over Southeast Michigan today. The most up-to-date guidance supports the cold front passage through the cwa between 12-16Z. First item noted is the deep layer (18000 ft deep) in the "warm sector" of neutral stability, i.e. no midlevel inversion and associated speed max. This is important because when initial low level cold air advection kicks in this morning, there isn't much of an environmental wind profile to mix into. The second item that is noted, is just how different the model data looks now versus what was provided in the days 3 to 5 timeframe. Fairly obvious now the northern and southern PV anomalies will maintain separation with no tangible phasing that impacts Southeast Michigan. The net result is a relative weaker area of surface low pressure today that is farther north. This impacts the curvature of parcel trajectories which is crucial in forecasting the presence and degree of dynamically active low to mid level subsidence. System relative trajectories maintain previous trends and show even less efficency with downglide, flow is not orthogonal to the isentropes. Latest guidance continues to show downward vertical motion into the surface limited from roughly 820- 850mb during the early afternoon hours. Forecasted environmental profiles suggest windspeeds of up to 45 knots available for a short time midday before deep mixing diffuses momentum into the 30 to 40 knot range by late afternoon. Given the number of factors lining up for slightly weaker windspeeds (in a relative sense) did lower the max windgust forecast by several knots. The current forecast will read winds today to range between 40 to 50 mph. The Wind Advisory remains in effect with the peak of the event expected between Noon and 6 PM. The last thing noted is a significant amount of 850-750mb cold air advection that will eventually push into Southeast Michigan between 00-06Z tonight. This will steepen lapse rates further and promote deep mixing potentially through 6.0 ft agl between 00-03Z tonight. Did think about extending the Wind Advisory for a few hours this evening, but since forecast gusts this afternoon were lowered did keep to previous messaging. A very low chance for some snow shower activity north of I 69 tonight given cold cyclonic flow. Did look through soundings and depth of moisture is somewhat shallow depending on what model one looks at. Did not introduce PoPs for tonight. Temperatures will be considerably cool Tuesday through Friday with daytime temperatures running in the 40s. The potential exists for some iso-sct light rain/sprinkle activity Tuesday particularly north of I 69. && .MARINE... Active marine weather in store for today as a couple of weather systems travel across the Great Lakes and phase across Ontario/Quebec late tonight through Tuesday morning. Active deepening of the low pressure will allow a strong pressure gradient to develop across the Great Lakes while also allowing a cold front to to pull across the state through the afternoon, increasing mixing depths and pulling in strong winds aloft down to the surface. This combination will produce likely gales across the marine areas along with storm force gusts for northern Lake Huron. Persistent gale to storm force gust will persist for the better part of the day and through the evening, with an eventual weakening trend expected throughout Tuesday morning as the low occludes and is removed from the general area. As a result, Gale and Storm Warnings hold for today. Westerly wind direction will come with the ramp up in wind speed, which will quickly elevate waves across the central and eastern side of Lake Huron. && .PREV DISCUSSION... Issued at 1147 PM EDT Sun Apr 12 2020 AVIATION... Light rain will persist off an on during the pre dawn hours. Low level moisture advection will also support a drop in ceiling heights. Ceilings have been slow to drop too much thus far. Upstream observations along with recent model soundings do still suggest a drop to low end MVFR and/or IFR ceilings prior to daybreak. The intensification of low pressure to the northeast will drive a strong cold front across the terminals around 14Z Monday. A strong low level wind field and increasing post frontal mixing will support west wind gusts up to and possibly over 40 knots into late Mon afternoon. For DTW...The passage of the cold front is expected between 14Z and 15Z and will be marked by a wind shift to the west with a rapid increase in speed. DTW THRESHOLD PROBABILITIES... * High for cigs aob 5k feet tonight and Monday. * High for exceeding crosswind thresholds from 270 degrees after 14Z Monday. * Low for thunder in KDTW airspace 09-14z Monday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Wind Advisory from 10 AM this morning to 8 PM EDT this evening for MIZ047>049-053>055-060>063-068>070-075-076-082-083. Lakeshore Flood Warning from 10 AM this morning to midnight EDT tonight for MIZ049-054-063. Lake Huron...Gale Warning from noon today to 4 AM EDT Tuesday for LHZ363-421-422- 441>443-462>464. Storm Warning from 2 PM this afternoon to midnight EDT tonight for LHZ361-362. Lake St Clair...Gale Warning from 10 AM this morning to 10 PM EDT this evening for LCZ460. Michigan waters of Lake Erie...Low Water Advisory from 10 AM this morning to 4 AM EDT Tuesday for LEZ444. Gale Warning from 10 AM this morning to 10 PM EDT this evening for LEZ444. && $$ DISCUSSION...CB MARINE.......CB AVIATION.....SC You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.