


Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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202 FXUS63 KDTX 140353 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1153 PM EDT Tue May 13 2025 .KEY MESSAGES... - Above average temperatures persist through the week. - Scattered showers/thunderstorm chances Wednesday. - A Slight Risk (2/5) for severe thunderstorms exists Thursday night primarily between 11pm and 3 am. The potential for large hail and damaging winds appear to be the main threats. - Cooler and less humid weather is anticipated for next weekend. && .AVIATION... A downward trend in shower coverage and intensity continues through the late night on the north fringe of slow moving Ohio valley low pressure. A wide range of ceiling conditions also follow a nocturnal transition into more widespread MVFR and then into IFR/LIFR with a fog component toward sunrise. Any larger breaks of clear sky have potential to result in a quick drop into IFR given T/Td in the 60s with only a few degrees of spread. Conditions are slow to improve during the morning as the surface trough moves toward and then into Lower Mi during the afternoon to combine again with daytime instability for another round of showers into Wednesday evening. For DTW/D21 Convection... An isolated thunderstorm is possible Wednesday afternoon but with low predictability on timing and location. THRESHOLD PROBABILITIES... * High for ceiling aob 5000 feet through the forecast. * Low for ceiling/visibility below 200 ft and/or 1/2 SM late tonight and early in the morning. * Low for thunderstorms Wednesday afternoon and evening. && .PREV DISCUSSION... Issued at 333 PM EDT Tue May 13 2025 DISCUSSION... An axis of deep moisture with connection to the Atlantic and Gulf is in place across Southeast Michigan. The PWAT on the 13.12z DTX raob was 1.40 inches and areawide surface dewpoints are in the 60s. The next few days, through midday Thursday, will be governed by moist adiabatic lapse rates that will bring periodic chances for showers and isolated thunder activity. The most favorable timing for convective development both today and Wednesday will be with daytime heating. Light easterly flow with low LCL heights limits much in the way of convective vigor. It is challenging to offer much temporal or spatial detail to the precipitation forecast as the EPS interquartile range of 24 hr QPF at all locations is less than 0.33 of an inch each of the next few days. The arrival of the exit region to a strong pacific jet streak will cause geopotential height falls to impact Southeast Michigan Thursday night. Latest indications are that midlevel cooling will occur in advance of the upper level low to result in steep midlevel lapse rates exceeding 8 C/km. Recent model solutions have been converging on a UVV signal that suggests the best time period for thunderstorm activity will fall in the 03-07z time window. Combination of the lapse rates with rich thetae/moisture from the surface to 5.0 kft agl is expected to result in very unstable conditions, CAPES of 2000-3500 J/kg. Despite the late evening to overnight timeframe, it is important to point out that confidence is increasing in this magnitude of instability owing to the lapse rates. The uncertain aspect of the forecast is to what extent the near surface convective inhibition will erode which will impact both the coverage of activity and the potential for surface based impacts. 0-6km bulk shear magnitude is forecasted to increase to greater than 40 knots Thursday evening resulting in the potential for mesocyclones and supercellular storm organization. Will need to monitor forecast trends as this time period approaches. The latest Swody3 has the majority of the forecast area in a Slight Risk for severe weather. Cool northwest flow is likely for next weekend as deep troughing remains in place over the Great Lakes. Depending on timing of successive cold fronts or lake breeze boundaries, the temperature forecast will be up for revision. MARINE... A weak pressure gradient continues to maintain lighter southeast flow through the midweek period with bouts of isolated to scattered showers and possibly some embedded thunderstorms. A warm front will then pass over the Great Lakes late Thursday night into Friday, which will veer wind direction to the southwest and will bring some more elevated wind speeds and gust potential. Additionally, some more organized thunderstorms will be possible along the warm front, centered through Friday morning. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....BT DISCUSSION...CB MARINE.......AM You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.