Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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957 FXUS63 KDTX 240721 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 321 AM EDT Tue Sep 24 2024 .KEY MESSAGES... - Seasonable temperatures through the early and mid week period. - Showers are likely today and tonight, with a chance of non-severe thunderstorms. - Most areas will receive around a half inch of rain or less, but localized totals in excess of 1 inch will be possible. - A few widely scattered showers possible Wednesday. Otherwise, drier conditions through the rest of the week with temperatures trending back above normal. && .DISCUSSION... Broadening corridor of northward moisture transport underway in the form of extensive cloud cover and some pockets showers early this morning. This process governed by a modest increase in mid level southwest flow immediately downstream of pending height falls tied to an elongating upper trough set to arrive late today. These conditions will largely define much of the daylight period, as interludes of greater isentropic ascent working across the advancing elevated warm frontal zone contribute to intervals of generally light shower production. Insolation potential minimized with a lack of sun, while the low level gradient holds from an easterly direction. This ensures a limited diurnal temperature response, capping afternoon temperatures in the upper 60s to lower 70s. Prospective secondary convective response between 20z and 03z along the east flank of the surface low and warm frontal intersection offers greater potential for a brief uptick in rainfall intensity. General consensus of model sounding data shows meaningful depth to the instability with a skinny cape profile, with upwards of 1000 j/kg of mlcape nosing across the Ohio border. Limited residence time of any clusters will preclude a greater flooding threat. Given the track of the surface low, a localized increase in both magnitude and depth of shear remains plausible across far southern sections. While the lack of greater magnitude of destabilization would seemingly work against establishing deeper rotating updrafts and a corresponding sig wx threat, the pattern from a synoptic level gives pause and remains worthy of monitoring as future CAM cycles and observational trends arrive. Amplifying mid level trough trailing the lead wave arrives Wednesday, effectively drawing the cold front across southeast Michigan through the day. Modest frontal convergence in the presence of sufficient moisture quality and diurnal destabilization points to widely scattered shower development targeting the late day period. No meaningful airmass change this period, as temperatures again push into the 70s. Benign weather conditions for the late week period. Deep column drying with increasing stability Thursday as mid level northwest flow briefly exists atop surface high pressure. A 589 dm upper high then takes residence Friday, ensuring moderating temperatures with continued dry conditions to finish the week. Attention shifts to the south as a large closed system centered over the mid/lower Mississippi valley interacts with a tropical system forecast to make landfill over the eastern Gulf coast sometime Thursday. Southeast Michigan still likely outside the main influence of this height fall center at least early during the weekend period, but with rainfall chances steadily climbing as the system lifts east by the latter half of the weekend. Further revision to precipitation chances expected. && .MARINE... Light east-southeast winds (mainly 10-15 kts) this morning as an area of low pressure tracks through the Central Great Lakes late today and tonight, maintaining the lighter winds. Numerous showers with a slight chance of thunderstorms will accompany the low. Large area of high pressure building in Wednesday night-Thursday will lead to light northwest winds, becoming northeast to end the work week as the high moves off into Eastern Canada and low pressure lifts north out of the Southeastern United States. The pressure gradient will be tightest over Lake Erie, and gusts reaching at or above 25 knots appear likely Friday-Saturday morning. && .HYDROLOGY... Low pressure brings scattered to numerous showers and a chance of thunderstorms today and tonight. Basin average rainfall is forecast to be between one quarter and one half inch, but totals in excess of 1 inch will be possible where any training storms develop. Flooding is not likely but there is the potential if any heavier rainfall axis does develop over the urban corridor. && .PREV DISCUSSION... Issued at 1050 PM EDT Mon Sep 23 2024 AVIATION... IFR/MVFR stratus has broken up to a degree KFNT south and cleared from KMBS entirely this evening. Expect trends to reverse overnight as coverage of lower stratus once again increases within northeast flow regime north of warm front. Low pressure to the southwest will encroach on area and force another period of showers by Tuesday morning along the upslope of this warm front. Low clouds and fog also solidify into IFR within the frontal zone and along the track of the surface low that is expected to move slowly across Lower Mi during the day and bring an additional period of rain later in the day as it moves into the region. During this period, a decent band of instability will lead to a better chance of embedded thunder and will introduce a prob30 group as far north as KFNT. For DTW/D21 Convection...A stray rumble of thunder remains possible late tonight and Tuesday morning as the next low pressure system approaches from the MO valley, but better thunderstorm chances will come after 22z Tuesday afternoon/evening. DTW THRESHOLD PROBABILITIES... * High for ceiling at or below 5000 feet tonight through Tuesday. * Low for thunder after 12Z Tuesday, medium after 22z. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...MR MARINE.......SF HYDROLOGY....MR AVIATION.....DG You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.