


Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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319 FXUS63 KDTX 081809 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 209 PM EDT Tue Jul 8 2025 .KEY MESSAGES... - Dry and seasonable conditions today. - More humid conditions return tonight and Wednesday, bringing an increasing potential for showers and thunderstorms. Severe weather is not anticipated with this activity, but locally heavy rainfall and gusty winds are possible. - Lesser potential for showers and thunderstorms Thursday as drier air works back into the region. Dry and warmer conditions then expected Friday. && .AVIATION... High pressure currently over the area will keep winds light with some sct diurnal cu around today. Winds will emerge out of the west/southwest ahead of a weak trough approaching this evening. Warm front lifting through this evening tied to a weak low may spark a few widely scattered showers after dark with the best chance of affecting MBS. Better chance of showers and possible thunderstorms comes tonight after midnight when the first mid level system lifts through SE MI. Trailing front could stall across the area keeping showers going after 12Z from FNT southward. Will leave out of the TAFs right now in favor of noting the frontal passage later in the afternoon which could bring another round of storms after 18Z. For DTW/D21 Convection... No convection through the daylight hours today. Low confidence on timing and occurrence of showers/storms in the vicinity mainly after 06z Wednesday. Convection could remain in the vicinity through the morning but better chance of renewed activity will be after 20Z. THRESHOLD PROBABILITIES... * Low for thunderstorms after midnight into Wednesday morning, and again Wednesday later afternoon. && .PREV DISCUSSION... Issued at 343 AM EDT Tue Jul 8 2025 DISCUSSION... Lower amplitude westerly flow to govern conditions through this afternoon. General mid level subsidence atop pervasive surface high pressure will maintain a high degree of deep layer stability and corresponding benign conditions. Limited moisture quality throughout the column ensures high insolation potential, lending a boost to an already moderating thermal profile off the notably colder readings from yesterday. Afternoon readings back to around early July norms - highs low to mid 80s. Minor shortwave energy lifting through the mean flow will offer some reduction in mid level heights beginning tonight. This process will draw a weak warm front through the region, while establishing a period of greater moisture advection overnight. Signal remains across the model spectrum for associated ascent to prove sufficient in generating some widely scattered nocturnal showers and thunderstorms across the lower peninsula. A more focused, higher probability of precipitation could materialize by late tonight/Wed morning should a greater corridor of dcva emerge tied to a passing pv feature. Broad lower amplitude mid level troughing established for the Wednesday period, as the main height fall center/closed low pivots across Ontario. Trailing surface trough arrives for the daylight period and offers a primary focus for additional convective development. Early day cloud/shower potential could dampen the pace of diurnal destabilization for at least a portion of the area, while also potentially establishing a greater differential heating boundary to provide an additional focus. In general, a modest level of instability projected. This in combination with a lack of a greater wind field suggests simply garden variety activity. The elevated moisture content again brings potential for any water loaded updrafts to generate locally higher rainfall rates and gusty winds during the afternoon and evening. Weakly cyclonic mid level flow will persist into Thursday. A potential transition day as drier air upstream attempts to arrive during the daylight period as northwest flow emerges upon exit of low level troughing. Mixed signal yet regarding pace of this process, thus leaving the door open for east/southeast sections to maintain an adequately moist and weakly unstable environment to support a lower end chance of convective development. Further revision of rain chances likely this period. Greater stability as low to mid level ridging arrives lends to higher confidence for dry conditions Friday. Corresponding increase in mean thicknesses would also support a modest warming trend to finish the week. Conditions appear more unsettled for at least a portion of the weekend period, as a more dynamic wave projects to lift across the great lakes. Scattered to numerous showers and thunderstorms already highlighted by latest NBM output for Saturday. MARINE... Light and variable winds to start as the surface pressure field trends more diffuse. Favorable marine conditions are expected until the overnight hours as the next low pressure system drags a cold front across Lower Michigan. Winds then organize out of the ESE, ahead of the surface low, with a tightening gradient. Expect a period of showers and thunderstorms within a pre-frontal warm sector for the southern waterways and activity along the cold front further north, moreso for Lake Huron. Ambient dynamics are rather weak which should keep prevailing conditions below Small Craft Advisory criteria, but locally higher winds/waves are possible with some stronger storms. Additional isolated to scattered convection is possible Thursday, particularly south of Lake Huron. HYDROLOGY... Scattered to numerous showers and thunderstorms are forecast Wednesday. Storms will be relatively disorganized, but with humid conditions and slow storm movement, storms will be capable of producing torrential downpours. Localized areas may receive over 1 inch per hour, which may lead to flooding of urban areas, small streams, and otherwise poorly drained areas. The main threat for flooding will be between 1pm and 8pm. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....DRK DISCUSSION...MR MARINE.......KGK HYDROLOGY....MR You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.