Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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766 FXUS63 KDTX 230714 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 314 AM EDT Mon Sep 23 2024 .KEY MESSAGES... - Seasonable temperatures through the early and mid week period. - Showers are likely Tuesday and Tuesday night, with a slight chance of non-severe thunderstorms. && .DISCUSSION... Southeast Michigan will reside between high pressure across the northern great lakes and a stalled frontal zone over the Ohio valley to start the work week. Higher quality low level moisture left in the wake of an exiting low pressure system ensures plentiful cloud cover through at least the first half of the day. Some late day breaks plausible as ongoing drying in low level northerly flow works to capitalize on diurnal mixing. Overall moisture quality lacks depth to suggest a more meaningful rainfall chance is possible, but can`t rule out a few stray showers mainly across the thumb region. Notably cooler relative to recent days, but still within the range of average for late September. Highs upper 60s to lower 70s. Mid level wave noted on water vapor ejecting across the central plains early this morning on pace to arrive locally Tuesday. This trajectory will draw the elevated frontal zone into the area, establishing a focus for some light shower production as early as late tonight and Tuesday morning under modest isentropic ascent. Pockets of showers will continue to manifest late Tuesday into Tuesday night as the inbound height falls and attendant surface low impinge on the area. Higher precip probability edged toward the south given closer proximity to both better moisture depth and forcing. Trailing mid level wave will gradually amplify across the region heading into Wednesday. Depending on the eastward pace of the frontal zone, this could afford a secondary response. Latest NBM guidance holding firm with a dry forecast this period. Seasonable resident thermal profile will continue to mark conditions, with an elevated dewpoint maintaining a relatively humid environment. Emergence of deeper layer northwest flow within the backside of the exiting high amplitude trough will then establish a more meaningful drying trend Thursday, with low-mid level ridging supporting dry conditions and a moderating trend to finish the work week. Expansive closed low positioned south of the area will be influenced by a tropical system/moisture rotating through the expansive periphery, eventually opening the door for some impact locally toward next weekend or early next week as the large scale feature finally releases eastward. && .MARINE... North-northwest flow will gradually veer to the northeast through the day today in the wake of a cold front. Modest mixing depths and a tightening pressure gradient in response to a departing low pressure system will support sustained winds shy of 20 knots across Lake Huron, with gusts to or below 25 knots. This will bring elevated wave heights around the tip of the Thumb, where Small Craft Advisories are in place. A ridge will fill back in later this afternoon through early tomorrow morning, lowering wind speeds and bringing dry weather. This will quickly be disrupted by a second low pressure system which moves over central Michigan tomorrow evening to Wednesday morning. This will bring another round of widespread rain showers, with some possible thunderstorms. && .HYDROLOGY... Low pressure system tracking through the region will bring a good chance of showers Tuesday and Tuesday night. Isolated thunderstorms also possible Tuesday afternoon and evening. Basin average rainfall between one quarter and one half inch. No flooding expected. && .PREV DISCUSSION... Issued at 1139 PM EDT Sun Sep 22 2024 AVIATION... Area of rain associated with passing low pressure will continue to work slowly east into the overnight with some degree of fog/drizzle left in its wake into Sunday morning as IFR/possible LIFR stratus spreads east/southeast into the area. Cigs will then increase into Monday afternoon within slight drier northerly flow, but with some potential of lower stratus/fog returning late Monday night. For DTW/D21 Convection...Thunderstorms are not expected during this forecast period. DTW THRESHOLD PROBABILITIES... * High for ceilings at or below 5000 feet into Monday morning, medium by Monday afternoon/evening. * Low for ceilings at or below 200 feet early Monday morning. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-441. Small Craft Advisory from 10 AM this morning to 10 PM EDT this evening for LHZ442-443. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...MR MARINE.......AM HYDROLOGY....MR AVIATION.....DG You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.