Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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440 FXUS63 KDTX 080401 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1201 AM EDT Wed May 8 2024 .KEY MESSAGES... - Showers and storms have concluded for tonight. - Warm and breezy conditions expected Wednesday, followed by cooler conditions and a chance of rain Thursday. && .AVIATION... Bulk of convection has cleared out of Southeast Michigan late this evening while a wave of subsidence leads to aggressive dissipation of clouds. Wind speeds trend lower for several more hours offering potential for periods of MVFR fog. After evening rainfall moistened the near surface layer, air temperatures should largely cool-down and approach the dewpoint temperatures, thus the current TEMPO. Can`t completely rule out areas of IFR fog given the underachieving gradient wind (and nearby obs), but low confidence exists. Sunny and breezy conditions arrive Wednesday afternoon with gusts in excess of 25 knots. For DTW/D21 Convection... A line of storms crossing Lake Michigan will dissipate before reaching the immediate airspace between 06Z and 08Z. Showers, and perhaps a rumble of thunder, possible early Thursday morning with the next system. DTW THRESHOLD PROBABILITIES... * Low for ceiling at or below 5000 feet this morning. && .PREV DISCUSSION... Issued at 346 PM EDT Tue May 7 2024 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 advection 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. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....KGK DISCUSSION...CB MARINE.......KDK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.