FXUS63 KDTX 091924 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 324 PM EDT Thu Jul 9 2026 .KEY MESSAGES... - Scattered to numerous thunderstorms continue through the evening hours across all of SE Michigan. - Isolated damaging wind gusts and locally heavy rainfall are the primary hazards with the severe threat waning after sunset. - Dry weather and near-normal temperatures settle in for the weekend. - A new heat wave is on schedule for next week (3 consecutive days of highs 90+ degrees). && .DISCUSSION... Scattered to numerous thunderstorms have developed across SE Michigan this afternoon, with varying depths to the convective cores. The deepest cores have topped out around 25.0 kft agl, likely after encountering the subsidence bubble that resides in the 15.0- 20.0 kft layer and an otherwise modest lapse rate environment. Peak wind gusts in these cells have so far remained below severe limits, although a few have come close. Storm motion around 20-30 mph brings the back edge of the storms currently near Lansing through the Detroit Metro area by 7 pm or so. A more organized line of thunderstorms is ongoing across northern Lower Mi right along the surface cold front, moving east-southeast. Convection along this boundary will clip portions of the Saginaw Valley and the Thumb early this evening, although the front itself will be relatively slow-moving. Thermodynamics are favorable for a few storms to become severe this evening, with MLCAPE values of 1000-1500 J/kg in place (SPC mesoanalysis) and dewpoints still in the upper 60s-low 70s. Wind gusts of 40 to 60 mph and heavy rainfall with rates in excess of an inch per hour are the main concerns. The frontal zone gradually sinks across Lower Michigan overnight, with models varying in how aggressively this occurs and if any of the convective activity can hang on as instability wanes. Most models settle the surface convergence and moisture axis north of the state line through Friday to renew scattered shower and thunderstorm chances during the day, mainly south of M-59. Similar to today, moist boundary layer conditions result in mid-day destabilization and an early afternoon start to convective initiation. Precipitation loaded cores again look to the be main concern as lapse rates will be modest around 5.5-6.0 C/km. The strongest cells will thus be capable of producing rainfall rates in excess of 1 inch per hour and localized downburst winds of 40-60 mph. Surface pressure rises begin Friday night as Canadian high pressure expands south into the Great Lakes, coinciding with a building western CONUS ridge. This releases the front fully south and clears out remaining moisture to bring PWAT values below 1" Saturday. This also effectively steers the next mid-level wave into the southern Ohio Valley, maintaining an overall dry forecast for the weekend. Core of the thermal trough stays over New England, with SE Michigan on the western periphery of the thermal gradient. Northeast flow keeps us within a fairly stagnant thermal advective regime maintaining seasonable highs in the low-mid 80s. Building heat dome over the Intermountain West becomes dislodged by a deep low over northern Canada, causing it to spill around the ridge and into the Great Lakes region early next week. Temperatures climb into the upper 80s Monday and likely into the low 90s Tuesday- Wednesday. This will bring heat indices into the mid-upper 90s. Less confidence in heat potential for the back half of the week however with much of that depending on how the upstream ridge and northern stream low interact. Positioning of the ridge to our west and resultant NW flow pattern do look to put us in a favorable corridor for convection, which will also influence temperatures next week.&& .MARINE... A weak cold front settles southward across Lake Huron this afternoon and evening before stalling or washing out near Lake St. Clair and western Lake Erie overnight into early Friday. Scattered showers and thunderstorms will continue to develop mainly south of the front during this period, with isolated storms capable of producing wind gusts in excess of 34 kt. Otherwise, ambient light wind will veer from west/southwest to north/northeast as the front passes through. High pressure builds across the northern Great Lakes on Friday which maintains north to northeast wind of 10 to 15 kt. Gusts may briefly reach near 20 kt in the afternoon across southern Lake Huron and Saginaw Bay due to favorable fetch orientation. Lingering showers and storms are possible mainly in the south. The high pressure eases farther south on Saturday and Sunday, maintaining mostly dry conditions with light northeast wind. && .HYDROLOGY... A slow moving cold front settles through southern Lower Michigan tonight serving as the focus for numerous showers and thunderstorms. The greatest coverage and intensity is expected to continue through the evening with a chance of locally heavy rain across the area. Basin average rainfall of a quarter to a half inch is most likely with a chance of near 1 inch in scenarios with greater thunderstorm coverage. The slow movement of the front could also produce more than one round of thunderstorms leading to localized totals greater than 1 inch within a few hours time. This presents minor urban flooding potential along with ponding of water on roads and in other prone areas. Scattered showers and a chance of thunderstorms lingers into Friday, mainly south of M-59, before coming to an end Friday afternoon. && .PREV DISCUSSION... Issued at 154 PM EDT Thu Jul 9 2026 AVIATION... Convection will be the primary aviation concern for the rest of today and early tonight. Several rounds of thunderstorms have already cropped up during the early afternoon hours. A band of showers continues to track south-southeastward, stretching from the Tri-Cities/Thumb to Lansing. This activity should largely remain lightning-free at MBS, although FNT has a chance to get clipped within the next hour by a strong storm tied to the southern end of the precipitation band. Meanwhile, further south, coverage is lower with loosely organized thundershowers that appear to miss the Metro terminals in the very near-term. Storm count will increase by late afternoon with a few multicell storms hitting the southern sites, plus another round potentially affecting MBS/FNT. This comes as a cold front currently draped over northern Lower Michigan tracks southward. Low confidence exists in the timing of any intercept for a specific terminal today; therefore, TEMPOs will continue to address afternoon and evening convection potential. The front slows over southern Lower late this evening by the time it reaches PTK, but any residual convection should be decaying. Unlikely for any activity to persist into the early morning hours on Friday, but still not impossible. Ceilings broadly start off as VFR, with MVFR closer to the frontal boundary. Some signal exists for fog development Friday morning, so added an entry-level MVFR mention. D21/DTW Convection...Scattered thunderstorms expected this afternoon and evening, primarily between 19Z and 02Z. Several rounds of storms and/or VCTS possible before Friday morning. DTW THRESHOLD PROBABILITIES... * Medium for thunder this afternoon and evening. * Medium for ceilings at or below 5,000 feet this afternoon and evening. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...MV MARINE.......TF HYDROLOGY....MV/BT AVIATION.....KGK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.