Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 250413 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1213 AM EDT MON JUL 25 2016 .AVIATION...
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After a convincing start during the early evening, thunderstorms continue to underachieve within the instability axis over lower Michigan. Suspect activity is mostly elevated with a few cells reaching moderate intensity and then settling back down again to more ordinary strength without really tapping full CAPE potential. Observational evidence really does not support much more except possibly some increase in coverage for the balance of the night before the broken line and clusters exit SE Michigan within the 10- 12z timeframe. A few hours of MVFR ceiling and visibility is expected with the frontal passage followed by improving aviation conditions in all areas during the day. Northwest wind has potential to gust near 20 knots as it brings still warm but less humid air into the region. For DTW... Showers/storms over central and southwest lower Michigan still have a chance to develop eastward toward the terminal. These are timed into DTW in 06-09Z time range and will likely exit all of SE Michigan 10-12Z. MVFR ceiling/visibility in fog will be swept in by the cold front with or shortly after the main area of showers/storms followed by improvement by mid morning. //DTW Threshold Probabilities... * Moderate for thunderstorms between 06-09Z. * Moderate for ceilings at or below 5kft toward sunrise through early morning.
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Issued at 927 PM EDT Sun Jul 24 2016 UPDATE... Mid evening mesoanalysis indicates MLCAPE pushing 3500 J/kg over SW lower Michigan at press time with the instability axis extending northeast toward Saginaw Bay while decreasing to "only" 2000 J/kg. That being the case, convection so far has struggled against larger scale subsidence and low level capping as shown in the DTX evening sounding. The APX sounding is more representative of incoming conditions with less of a cap but still relatively weak mid level lapse rate. This is also expected to change as the upper ridge overhead moves eastward in favor of weak height falls/cyclonic flow over the Midwest. Hourly mesoanalysis shows this as an area of steeper 700-500 mb lapse rates over southern WI/northern IL set to move into lower Michigan. There is also good potential for a component of lapse rate increase due to radiational cooling aloft within the dry layer above 600 mb. These elements will provide a more favorable environment for storms to develop and persist within a gradually decreasing instability axis along and ahead of the cold front as it moves through SE Michigan overnight. Expect scattered to numerous coverage with most activity to our east around 12z. The SPC marginal risk for severe looks good for just a few of the strongest storms in this high CAPE/low shear environment. Downburst wind will be the main concern but only within deeper cores or longer lived multicell clusters. PREV DISCUSSION... Issued at 311 PM EDT Sun Jul 24 2016 DISCUSSION... MCs that has been slowly passing across southeast Michigan will continue to weaken this afternoon as it exits. Temperatures remained quite steady during the day a bit far from forecasted highs but as clouds thin, several hours of decent amount of sunshine the rest of this afternoon and evening will push most location into the 80s. Two boundaries remain across the area that will be the main focus for convection the rest of the day. One outflow boundary is laid out across central lower from about Saginaw bay/Thumb westward and the other is from about Toledo back to southern Lake Michigan. Broken line of showers and thunderstorms have developed along the northern boundary but have been weakening somewhat as it pushes southward away from main cold pool aloft. Expect this boundary to make it near i69 corridor before stalling this evening. The better chance for shower and thunderstorm development will be more westward were the better instability lies. The southern boundary is a bit stronger as a result from the cooler air from todays MCs and substantial heating across northern Indiana as this area has had a good amount of sunshine all day. Expecting regeneration of storms along this boundary from nw Ohio back into sw lower Michigan. Most activity should remain south and west of the cwa but some showers could spill over into Lenawee and Monroe counties as main flow aloft is from the southwest. Main cold front is moving through eastern Wisconsin and that will push slowly through the area overnight. Not much dynamical forcing with the front, just mainly surface convergence. Southeast Michigan will not likely get into the good deep instability as that will remain to our south, shunt off by todays MCs and boundary to the south. Only expecting scattered showers and thunderstorms to accompany fropa. The front should be close to exiting the area around sunrise. Will still carry a chc for precip far southeast corner Monday morning as this area will still be close to the front. Drier air will slowly work in behind the front with dewpoints starting off the day still in the upper 60s in the north to lower 70s south but dropping a 10 or so degrees by end of day. With plenty of moisture in the boundary layer, expect a rapid development of cu shortly after sunrise with clouds slowly thinning and diminishing throughout the day from nw to se. It will still be quite warm Monday as airmass behind front more drier then cooler. Zonal upper flow Wednesday over the Great Lakes will transition to cyclonic by the end of next week/weekend as a series of shortwaves act to carve out a trough. Midrange deterministic models time the lead disturbance for Thursday, so Wednesday will likely be another dry and warm day. Then, indications are that a low-level circulation attendant to the upper height falls will slowly track across the lower Great Lakes. This could focus a more well-defined period of precipitation, but still significant model spread with respect to the timing and placement, so have kept general chance PoPs Thursday through Saturday. Temperatures are expected to trend back toward normal late next week. MARINE... A cold front will move across the region tonight turning the winds from south/southwest to west/northwest. Speeds are expected to remain below 15 knots. High pressure will set the stage for light and variable winds on Tuesday. HYDROLOGY... Additional showers and thunderstorms are possible in advance of a cold front tonight. Widespread rainfall is not expected - however localized downpours are still possible, capable of totals up to an inch.
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&& .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....BT UPDATE.......BT DISCUSSION...DRC/DT MARINE.......Mann HYDROLOGY....Mann You can obtain your latest National Weather Service forecasts online at is the U.S. government's official web portal to all federal, state and local government web resources and services.