Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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872 FXUS63 KDTX 071946 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 346 PM EDT Tue May 7 2024 .KEY MESSAGES... - There is a chance of isolated to scattered strong to severe thunderstorms south of a Midland to Port Huron line this evening, the greatest chances are along/south of the I-94 corridor. - Damaging winds, large hail and isolated tornadoes are the severe weather risks. - Warm and breezy conditions are expected Wednesday, followed by cooler conditions with a chance of rain Thursday. && .DISCUSSION... Previous forecast reasoning offered by Area Forecast Discussions issued earlier today remains valid. Initial arc of elevated shower activity forced by lead system relative isentropic ascent and 850- 600mb thetae advection is now lifting northward through Southeast Michigan. After this initial evaporative cooling response, will be monitoring for the surface temperature and dewpoint recovery to gauge for the potential of surface based, severe thunderstorms between 6-11 pm local time. As forecasted, dewpoints have been slow to rise and will have to overcome a due easterly trajectory off of Lake Erie. A strong convergence bullseye on the nose of a deep kinematic field and upper level diffluence is forecasted to lift/pivot directly into portions of south central and southeast Michigan this evening. Quality of large scale forcing is expected to result in numerous to widespread showers and thunderstorms after. 22Z The main threat this evening will be a potential for a tornado (mainly for areas south of I 94) conditional to surface instability. The secondary threat with thunderstorm activity (all areas) this evening will be large hail. Modest midlevel lapse rates of 6-6.5C/km should limit hail diameter potential, but any non-hydrostatic force provided by mesocyclones could cause for hail diameters to exceed 1 inch. Again, the time period for potential severe weather is between 6-11 pm. The zonal gradient orientation in the wake of the upper level trough release will then set the stage for a relatively breezy day on Wednesday. West winds of 20 to 30 mph. Little to no northward advections will yield a sneaky warm day Wednesday with a dry, well mixed boundary layer. No humidity to speak of but sunny conditions and temperatures reaching the middle 70s to low 80s. A very complex upper level height configuration is then expected to develop for the Thursday and Friday time frame. An atypical elongated trough axis is expected to reside in a largely west to east fashion from the Central Plains to the Central Great Lakes. Not a whole lot of confidence to be garnered from the setup as various shortwaves digging southward from central Canada will have the opportunity to disrupt the troughing. As it stands, Southeast Michigan looks to be in a fairly close proximity to deeper deformation forcing. Coupled jet forcing is also expected to eject trough providing for an ageostrophic response and increased frontogenesis. PoPs for Thursday are in the numerous to likely category for much of the area and is warranted. Various, lobes of modest planetary/potential vorticity are forecasted to dig through Southeast Michigan for this upcoming weekend. Given the trajectory, the predictability to the timing of the shortwaves may prove difficult, but current trends suggest Saturday is the most likely of time periods for precipitation. Temperatures will be strongly dependent on cloud cover, with current forecast suggesting temperatures of approximately 5 degrees below normal. && .MARINE... Warm front tied to Midwestern low pressure continues to lift into the central Great Lakes this afternoon supporting widespread showers as well as scattered thunderstorms into this evening. A few strong to severe storms are possible for areas south of Port Huron with all hazards on the table. System`s cold/occluded front crosses the region overnight setting up modest (~15-20kt) westerly flow for Wednesday. Secondary low development over the Ohio Valley Wednesday night results in a turn to northeasterly flow locally. Marginally cooler airmass is drawn south, combined with the still tightened gradient, is expected to allow for peak gusts 20-25kts over the central portion of Lake Huron with near 30kts possible over Saginaw Bay (lesser gusts over the remainder of the region). Additional showers are also likely daytime Thursday before the low vacates. && .PREV DISCUSSION... Issued at 217 PM EDT Tue May 7 2024 AVIATION... A line of decaying showers/storms is moving into Southeast Michigan this afternoon. An influx of low-level moisture brings cloud bases just above MVFR during the afternoon. Monitoring storm potential for this evening as low pressure tracks across Lower Michigan bringing a warm front, higher dewpoints, and strong shear with energetic jet winds aloft. Limiting factor for storm development/growth tied to questionable instability which struggles to become surface based as storms move in from the west. Timing for most of this convective activity falls between 6 PM and 9 PM with a slightly earlier start at MBS. Clouds try to scour out after midnight offering potential for a bit of MVFR fog as the humid airmass cools. Breezier day Wednesday with afternoon gusts in excess of 25 knots and VFR conditions. For DTW/D21 Convection... Scattered to numerous thunderstorms expected this evening with potential for some strong storms capable of 40+ mph gusts, hail larger than a half inch, and possibly a tornado or two within the vicinity. Scattered discrete storms are favored early before multicellular clusters move through later in the evening. Storms move from west to east at 40 mph between 6 PM and 9 PM. DTW THRESHOLD PROBABILITIES... * High for thunderstorms 23-02Z this evening. * Medium for ceiling at or below 5000 feet today, high during evening, then low overnight. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...CB MARINE.......KDK AVIATION.....KGK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.