FXUS63 KDTX 160913 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 513 AM EDT Mon Jul 16 2018 .AVIATION... VFR conditions this morning within a moist pre-frontal environment sustained under modest southwest winds. Blossoming high based diurnal cu field into the afternoon as a pre-frontal trough lifts into the region. Thunderstorm potential will subsequently increase through the afternoon period as this boundary and a cold front track across SE Michigan. Confidence in development remains high enough to maintain a defined mention centered on the mid and late afternoon periods. Cooler and drier conditions will accompany a post-frontal wind shift to northwesterly during the evening hours. This will effectively end the thunderstorm risk, while bringing clearing skies across the lowest 5000 ft. .DTW THRESHOLD PROBABILITIES... * Medium for cigs aob 5kft this afternoon. * Medium for thunderstorms between 19Z and 00Z. && .PREV DISCUSSION... Issued at 349 AM EDT Mon Jul 16 2018 DISCUSSION... Main story for today will be scattered showers and thunderstorms across much southeast Michigan during the afternoon and evening hours. A low pressure system swinging across Ontario throughout the day will drag an associated cold front through Michigan. There will be favorable diurnal timing of the front as it crossing through the Tri-Cities during the afternoon and far southeast Michigan by late evening. Placement of the jet will also provide some upper level support for convection along the cold front. The best forcing will be across the Thumb and Saginaw Valley where greater heights falls, better 0-6 km shear of 25-30 knots and lapse rates around 6 C/km reside. Hot and humid conditions ahead of the front will aid instability as MLCAPE values increase to around 1500-2000 J/kg. Moist environment can also be characterized by precipitable water values reaching 1.50 inches and up to 1.90 inches throughout the day. Given this environment, isolated severe storms will be possible across much of the CWA today with SPC placing all of southeast Michigan in a Marginal Risk. Main threat will be strong to potentially severe wind gusts from stronger storms with soundings showing inverted V profiles in the afternoon. Localized heavy rainfall will also be possible due to the higher atmospheric moisture. There is one limiting factor across southern portions of the CWA and that is the presence of some mid level capping with temperatures of 8-10 C around 700 mb. This may act to inhibit greater coverage potential in these areas. High temperatures today will be in the mid to upper 80s for most locations with increased cloud cover keeping temperatures from reaching any higher. This should be the last day of the work week with heat indices in the low to mid 90s before northwest winds behind the front help push the higher moisture out and bring in lower dewpoints. Dry air behind the front will help overnight drop to into the upper 50s to mid 60s. High pressure builds across the Great Lakes Tuesday through midweek with cooler and drier northwest flow aloft. This will allow for mostly sunny conditions and more seasonable high temperatures ranging in the mid 70s to low 80s. Mostly clear skies will allow for good radiational cooling and the lower dewpoints will help overnight lows on Tuesday night dip down into 50s with the exception of the urban heat island of Detroit metro. A low pressure system will become organized across the northern plains and meander eastward through the Great Lakes late this week through the weekend. A little too early to hash out exact details, but the system looks to bring unsettled weather conditions with increased chances for showers and thunderstorms beginning Friday and into the weekend. Temperatures look to remain in the 70s and 80s during this time. MARINE... Scattered to numerous thunderstorms expected during the afternoon and early evening hours as a cold front tracks through the central Great Lakes. Modest southerly winds through the daylight period, then turning northwesterly tonight behind the front. Some increase in wind speeds will occur overnight through Tuesday, but with gusts at 20 knots or less. Winds ease Wednesday under building high pressure. This high will sustain tranquil marine conditions through Thursday. HYDROLOGY... Moist conditions will exist today as a cold front advances across the region. This will bring a greater chance for showers and thunderstorms during the afternoon hours. While basin average rainfall amounts will likely remain below one half an inch, localized higher amounts in excess of one inch will be possible within bands of heavier thunderstorms. Some minor flooding of low lying and poor drainage areas may result. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....MR DISCUSSION...AA MARINE.......MR HYDROLOGY....MR You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.