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Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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818 FXUS63 KDTX 200722 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 322 AM EDT Sat Jul 20 2024 .KEY MESSAGES... * High pressure ensures another day of dry conditions with high temperatures in the low 80s. * Low chance for a showers and possibly thunderstorms Sunday and Monday afternoon. * Better potential for showers and thunderstorms middle of next week as weak low pressure and a cold front track through the northern Great Lakes. && .DISCUSSION... A stagnant upper level pattern, characterized by semi-permanent high pressure over SE CONUS and a slow-moving upper low near Hudson Bay, affords little change to local conditions from yesterday to today. Plenty of solar insolation is expected again to support a well-mixed boundary layer with temperatures reaching into the low 80s. Similar diurnal cumulus response expected as well, although with an added layer of high-based cirrus stemming from convective cloud debris originating in the Great Plains. Looking at the CONUS-scale, GOES-16 mid level WV loop depicts the two disturbances that will impact SE Michigan in the coming days. The first of these is a pair of shortwaves over southern Minnesota, which will evolve into a cut off low today and slowly pivot into the Great Lakes early next week. The second is the deformation axis which will supply a band of enhanced theta-e to central lower MI beginning on Sunday. The added moisture boost creates weak instability on the order of ~500 J/kg (MUCAPE) during peak heating, enough to trigger isolated to scattered showers across northern portions of the cwa Sunday afternoon. An isolated (non-severe) thunderstorm cannot be ruled out. Guidance signals for the upstream cut off low to open up and slowly get absorbed into the mean flow early next week. There are still major differences in the temporal and spatial placement of the upper low-wave transition. Precipitation chances and coverage will generally be tied to the interplay between lingering moisture and survival of the upper low circulation into lower Michigan. As of now, another low chance for showers exists Monday afternoon which will have a diurnal component tied to a broader plume of weak instability. A more dynamic system arrives mid-week, supportive of more widespread shower and thunderstorm chances. Upper trough influence throughout the forecast period maintains temperatures in the low to mid 80s. && .MARINE... A broad expanse of surface high pressure centered on Lake Erie ensures favorable marine conditions across Great Lakes during the early part of the weekend. Benign conditions then continue even as a weak cold front settles into northern Lake Huron Saturday night and across the south half during Sunday. The front brings a minimal temperature change and supports just a stray shower along and near the boundary leaving the SW to NE wind shift as the weather highlight. The directional wind shift is notable but wind speed remains light for a low impact wave pattern Sunday followed by the front washing out in favor of weak high pressure by Monday. && .PREV DISCUSSION... Issued at 1139 PM EDT Fri Jul 19 2024 AVIATION... High pressure extending across the southern Great Lakes will maintain light and variable winds through the morning. This high pressure system will dominate into Saturday night. The associated dry air will limit cloud coverage to just scattered diurnally driven cu. For DTW/D21 Convection...No convection is expected through the TAF period. DTW THRESHOLD PROBABILITIES... * None. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...MV MARINE.......BT AVIATION.....SC You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.