Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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460 FXUS63 KDTX 232307 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 707 PM 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 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. - Drier conditions through the rest of the week with temperatures trending back above normal. && .AVIATION... IFR/MVFR stratus will largely remain in place into tonight within northeasterly flow north of warm front with some moisture flux from Lake Huron. 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 moves into the region. 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. DTW THRESHOLD PROBABILITIES... * High for ceiling at or below 5000 feet tonight through Tuesday. * Low for thunder after 12Z Tuesday. && .PREV DISCUSSION... Issued at 353 PM EDT Mon Sep 23 2024 DISCUSSION... Relatively quiet conditions hold in place through the evening hours as high pressure over Wisconsin slides across the northern Great Lakes. Some breaks in the low stratus are occurring as the boundary layer mixes into drier air aloft, but satellite imagery shows plenty of additional mid-level and high clouds that will fill in from the south through the evening. So cloudy conditions will prevail, with mild temperatures in the 60s and lower 70s this afternoon settling into the 50s and 60s through the evening. Upstream MSLP analysis shows a surface low beginning to take shape over Missouri in response to a mid-level wave tracking into the area from the west. This wave will be kicked northeast tonight as a 100+ kt upper jet dives equatorward across the northern Plains. The surface low will continue to deepen overnight into Tuesday morning as it lifts toward lower MI, bringing with it a surge of deeper moisture characterized by PWAT near 1.50 inches. The elevated warm front will work in across the state line around midnight, continuing north through the morning hours. This may bring spotty showers at times during the early morning before more numerous showers fill in by the mid-morning as saturation is achieved through the column. Off and on showers will continue through the daytime and evening hours with a chance of non-severe thunderstorms. An item of interest will be the track/speed of the surface low and the subsequent placement of the warm front by the evening hours. The higher instability and attendant marginal severe threat will be held south of this front, but there are several recent model runs that carry the low a bit more quickly into SW lower MI by late afternoon. This would place the warm front and localized larger low-level hodographs in the vicinity of the I-94 and Metro Detroit corridor. If the trend continues, will need to keep an eye on this area as there would be potential for isolated strong or severe storms in the evening along the front/triple point. The track of the low will also have implications on any potential localized heavier rainfall axes as there is signal for slow-moving/training storms with enhanced deformation setting up just north of the surface low track during the late evening. Most areas are likely to see a half inch or less through the 24 to 36 hour period of showers, but if a heavier axis does set up totals in excess of 1 inch will certainly be possible along a localized swath. The low reaches Lake Huron by Wednesday morning before getting absorbed into a larger scale trough descending from Hudson Bay. This trough, tied to the aforementioned jet, will send additional PV energy over the region and may be enough to touch off isolated light showers on Wednesday. Otherwise, seasonable temps hold with some peeks of sun possible by late in the day. Dry northeast flow looks to dominate the area through the late week as we sit north of a deep cutoff upper low over MO/AR and within an induced blocking ridge. The late Friday and Saturday periods carry a bit more uncertainty as this upper low looks to slingshot a tropical system north into the Ohio Valley before absorbing it. The northward extent of the moisture transport will need to be monitored for future forecast adjustments, but for now will continue to carry a chance for showers. MARINE... Will allow the small craft advisory to expire late this afternoon, as wind speeds will be dropping just below 20 knots shortly, and wind direction will trend more easterly tonight, and then southeast Tuesday morning as an area of low pressure tracks through the Central Great Lakes Tuesday and Tuesday night. 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 Tuesday and Tuesday night. 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. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....DG DISCUSSION...TF MARINE.......SF HYDROLOGY....TF You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.