


Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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980 FXUS63 KDTX 062305 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 705 PM EDT Sun Jul 6 2025 .KEY MESSAGES... - Becoming drier, cooler, and less humid with time Monday and Tuesday. - Shower and storm potential returns mid-late week with temperatures trending above normal. && .AVIATION... Showers and thunderstorms blossomed on schedule in the warm and humid air out ahead of the inbound cold front during the afternoon. The storms moved east of MBS to FNT and are soon to exit the PTK to DTW area shortly after forecast issuance. That leaves the cold front left to slide through central and southern Lower Mi for the rest of tonight. There is lingering potential for showers as the 500 mb trough trails the surface front, and this activity could present some brief visibility reduction while ceiling becomes the primary limiting factor post front. Upstream ceiling observations across northern Lower Mi are borderline MVFR/IFR and set to move south on the northerly wind shift during the night. Not counting thunderstorm outflows this evening, the primary frontal wind shift reaches MBS around 02Z and then moves slowly but steadily south to DTW by about 09-10Z. MVFR ceiling then holds for several hours during the morning until breaking out into scattered VFR coverage for the afternoon. Light northerly wind continues through the day as high pressure gradually assumes control into Monday evening. For DTW/D21 Convection... As ongoing storms exit eastward, there is lingering low probability for thunderstorms tonight as a cold front approaches from the north and moves through the D21/DTW airspace until about sunrise. THRESHOLD PROBABILITIES... * High for thunderstorms until about 02Z this evening, then low overnight and into early Monday morning. * High for ceiling below 5000 ft between 06Z and 18Z Monday. && .PREV DISCUSSION... Issued at 303 PM EDT Sun Jul 6 2025 DISCUSSION... Denser cloud field gradually expands eastward across Southeast Michigan, ahead of a slow moving cold front bringing increasing coverage of showers and thunderstorms through the evening hours. Out ahead of this boundary, SSW winds reinforce a hot, muggy, and breezy airmass marked by dewpoints near 70F. Differential heating yields spatial differences in the distribution of peak instability as several showers and thunderstorms have already developed along the instability gradient where better shear is present. Some of the updrafts have been productive, featuring overshooting tops near minus 60C. Synoptic ascent associated low amplitude troughing aloft aids in the expansion of storm coverage with time as MLCAPE responds, but the underwhelming shear profiles still preclude widespread severe considerations. Main concern remains focused on the immense influx of pre-frontal water vapor which leads to the doubling of PWATs (see 06.12Z KGRB and KAPX RAOBs), compared to the 06.12Z KDTX RAOB (1.03 inches). This presents an isolated/marginal severe wind threat due to the potential for wet microbursts, in addition to some flooding for areas that might experience repeat torrential rainfall. Convective environment will be less favorable into Metro Detroit, located well ahead of the lagged frontal forcing, and displaced off the main instability axis. Certain CAM solutions suggest that activity could undergo rapid decay upon reaching the population center, especially if it takes until closer to sunset for the loosely organized cells to arrive. Higher uncertainty in precipitation potential exists during the overnight hours as the front`s progress further slows. While a signal for a reduction in coverage and intensity after dark is well advertised in the model data, the persistence of nocturnal instability, coincident with the frontal slope, supports pulse thunderstorms overnight. Progs show the anticipated wind shift and surface trough axis still not necessarily clearing the forecast area by 06Z. Pervasive post-frontal status spills in tonight which limits efficiency of nocturnal cooling and undercuts the advection of continental Canadian air, once surface flow veers northerly. Column moisture stays quite elevated Monday morning for areas south of I-96/I-696 with forecast soundings also showing minimal adjustments to thermodynamic profiles. This preserves some degree of instability for a few additional thundershowers until tropospheric winds shift westerly, drying out the mid-levels. Monday will be the coolest day of the week with highs running a couple degrees below normal. Expect upper 70s to near 80F for most, inland of the cooler Huron lakeshore. The cold front then stalls, becoming a stationary boundary locked in over the northern Ohio Valley as surface high pressure builds into the Great Lakes through Tuesday. This ensures a 24+ hour period of drier weather. Trough amplification takes place over the region Wednesday into Thursday, extending from a PV anomaly over Ontario that leads to the wave closing off as it crosses into western Quebec. Southerly flow sends the warmer stalled airmass over Ohio back toward southern Lower Michigan. This provides fuel for the next phase of diurnally driven summertime convection. Dewpoints also tick higher, perhaps back above 70F with vicinity upper-level divergence offering opportunities for some more robust updrafts. Shortwave ridging moves in Friday with low-end precipitation potential driven by MCS remnants from The Plains. MARINE... A slow moving cold front will move through the Central Great Lakes tonight, triggering numerous showers and storms this evening. Some of the storms may be strong, producing torrential rainfall and wind gusts of 45-50 knots. Behind the front, northerly winds look to top out around 20 knots over Lake Huron on Monday. Waves impacting the nearshore waters of southern Lake Huron still look to be mainly below 4 feet however. A few showers/storms could linger over Lake Erie into Monday before enough dry low level air works in toward the southern Michigan border. High pressure then briefly follows late Monday through Tuesday before unsettled weather returns midweek, with a chance of showers and thunderstorms. Even so, outside of any short lived storms, winds look to be light under 20 knots. HYDROLOGY... Thunderstorms continue to spread eastward this evening amidst hot and humid conditions. Storms will move rather slowly and be capable of producing torrential downpours. Rainfall rates in excess of an inch per hour are expected, but will occur in localized fashion. Narrow segments of ongoing storms have been sample by KDTX radar with estimated rates in excess of 4 inches per hour. This may lead to flooding over developed locations, small streams, and other areas subject to poor drainage mechanisms. The main time-frame for flooding will occur between 3 PM and 9 PM, until the supporting cold front works further southeast. This lends a decreasing in intensity and coverage of storms through the overnight hours. A few lingering showers/storms are possible Monday morning, mainly south of the I- 96/I-696 corridor. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....BT DISCUSSION...KGK MARINE.......SF HYDROLOGY....KGK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.