


Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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381 FXUS63 KDTX 101854 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 254 PM EDT Thu Jul 10 2025 .KEY MESSAGES... - Trending warmer into the weekend, with heat index into the mid to upper 90s on Saturday. - Increasing potential for showers and storms on Friday and Saturday with isolated severe storms and heavy rainfall/localized flooding possible each day. - Dry weather early next week with temps aoa 90 degrees on Tuesday. && .DISCUSSION... Morning fog and low clouds north of M-59 were slow to burn off, but temps are quickly spiking toward 80 degrees, with mid 80s south of M- 59. Surface dew pts in the mid to upper 60s leading to MLcapes aoa 1000 J/kg over eastern Thumb region with weak low level convergence/surface trough supporting isolated showers/thunderstorm. However, mid levels are very dry, and surface dew pts will be mixing down slightly late this afternoon, leading to diminishing instability from west to east, ending any shower/thunderstorm threat very shortly. Multiple opportunities for showers and strong thunderstorms into the Weekend, as the upper level wave/trough over Western Canada digs southeast and swings through the Great Lakes region. Lead upper level disturbances and deep/pseudo tropical moisture (PW of 2 inches/5+ C dew pts at 700 MB) over the Midwest/Central Plains will be tracking off to the northeast tomorrow and Saturday through the region, potentially in-sync with or close to the peak heating of the day. If that is the case, at least a marginal risk of severe weather exists with moderate instability, as MLcapes build between 1500-2000 J/kg (per HRRR/RAP/NAM/RRFS blend) on Friday (particularly along/west of U.S. 23) with precip loaded downbursts possible, despite 0-6 KM bulk shear mostly in the 25-30 knot range. Lead instability/moisture gradient arrives Friday morning (12-16z) before more robust surge arrives late in the day. If showers and possible embedded thunderstorms do in fact move in during the morning from decaying MCS and do not dissipate in timely fashion, previously mentioned capes and late day severe threat may be hindered. However, better instability and shear over northern Illinois may be able to develop another MCS, with organized system still potentially able to support severe storms over southern Lower Michigan early in the evening, and SPC has included parts of the CWA in a slight chance of severe for this reason. Even higher instability progged for Saturday as surface dew pts push into the lower 70s, presenting an even better chance of showers and strong to severe thunderstorms, especially if slightly better wind fields arrive by 00z Sunday. This deep moisture and relatively slow movement leads to a heavy rainfall/localized flooding threat (both Friday and Saturday), especially in any urban setting. With the higher dew pts and temps aoa 90 degrees on Saturday (ultimately dependent on timing of convection), heat indices may briefly rise into upper 90s/approach 100 degrees. Upper level trough axis to swing through the Central Great Lakes on Sunday. Enough low level moisture may still be around to touch off scattered showers and thunderstorms as the 12z Euro shows cold front slow to push east. Upper level ridge (591-592 DAM at 500 MB) axis then builds over the region early next, promoting dry but hot weather, with temps likely aoa 90 on Tuesday. && .MARINE... High pressure to bring mostly dry conditions, outside of a low chance for a stray shower, and calm to light winds through the day today and into tomorrow. Latest model trends now suggests a couple of possibilities for showers and thunderstorm potential tomorrow. The first coming from a decaying storm system that is expected to weaken as it travels into the eastern Great Lakes tomorrow morning and afternoon. It is possible some lingering thunderstorms can affect the region leading into the afternoon hours. A secondary round of showers and thunderstorms will then again move in from the western Great Lakes with some development possible overhead, which brings the potential to see strong to severe storms in the later afternoon and evening hours. Small hail and wind gusts in excess of 40 knots will be the main threats with any stronger storms. Additional shower and thunderstorm chances will enter this weekend ahead of and along a cold front. && .HYDROLOGY... The next period to monitor for potential heavy showers and storms is Friday and Saturday as a hot and humid air mass builds back into the region. The forecast for Friday carries a lot of uncertainty at this stage, but there is the potential for a thunderstorm complex to arrive from the west early in the day and act as a trigger for afternoon showers and storms. If this occurs, the environment would support heavy downpours with rainfall rates in excess of 1 inch per hour and slow storm motions leading to localized flooding concerns. Saturday presents a higher likelihood for showers and storms with a similar environment also supportive of a localized flooding risk. && .PREV DISCUSSION... Issued at 129 PM EDT Thu Jul 10 2025 AVIATION... Entrenched fog over the northern terminals is lifting/scattering early this afternoon with only patchy cumulus over areas south. VFR cu field persists through the daylight hours though coverage generally holds between FEW to SCT- greatest in the north. Decaying convection is set to work across lower MI Saturday morning however confidence in both its coverage and remaining thunder are low at time so have only introduced a Prob30 group for showers. For DTW/D21 Convection...Chance of thunderstorms this afternoon remains at less than 20 percent. THRESHOLD PROBABILITIES... * Low for an isolated thunderstorm this afternoon. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...SF MARINE.......AM HYDROLOGY....SF AVIATION.....KDK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.