Expires:No;;649811 FXUS63 KDTX 050701 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 301 AM EDT Sun May 5 2024 .KEY MESSAGES... - Decreasing clouds this afternoon and evening. Mostly sunny Monday. Seasonal temperatures. - Showers likely with a chance of thunderstorms Tuesday afternoon and evening. Strong to severe storms are possible south of I-94. && .DISCUSSION... Showers and isolated thunderstorms weakened and decreased in coverage as they inched toward Se Mi early this morning, the result of the upper jet support and mid level height falls lifting north of the forecast area. The convection also become outflow dominated, leading to waning instability. The associated surface front will also weaken as it exits east of the area this afternoon, although the 00Z hi res suite all indicate lingering sfc troughing extending across Se Mi into late afternoon. Sfc high pressure will expand into the western Great Lakes today as mid level ridging builds across the upper Mississippi Valley. Ample low level moisture along/ahead of the approaching front (sfc dewpoints around 60F) will contribute to low clouds and a few lingering showers this morning. Low level cold air advection this afternoon will deepen the mixed layer, boosting cloud bases and supporting afternoon highs well into the 60s to low 70s. Persistent low level anticylonic flow associated with the inbound sfc high will eventually drive drier air into Se Mi, leading to a late afternoon/evening clearing trend from north to south. The associated north-northeast sfc winds will also advect the Lake Huron marine layer inland during the course of the afternoon/evening. This will present itself as a notable drop in temperatures. Mid level ridging and associated sfc high pressure will be anchored over Lower Mi and Lake Huron by Monday. Occasional high clouds may be all that keeps skies outright clear. The strength of the subsidence will limit mixing depths Monday to just under 5k feet, resulting in daytime highs mainly in the mid 60s to near 70. The dry air and light winds will allow respectable nighttime cooling, both tonight and Monday night, leading to lows into the 40s. A highly amplified long wave trough is forecast to emerge from western Canada into the Central Plains Tuesday, becoming a deep closed low across the northern Rockies/High Plains by Wednesday. Strong deep layer southwest flow ahead of this system will drive an instability plume into the Ohio Valley on Tuesday. Upper jet support and strong moisture transport/convergence along a low level warm front will support increasing chances for showers/thunderstorms Tues aftn/Tues night. The northward extent of the surface based instability plume into southern Michigan carries some degree of uncertainty. While there is still a decent spread among ensemble members, the late timing of the front and easterly flow off the stable lakes suggests that surface based instability may struggle to advect too far northward into Se Mi. In light of strongly sheared environment and model uncertainty, the southern portions of Se Mi may remain on the northern edge of the SPC severe outlooks for the next couple days. && .MARINE... A weak cold front will continue to track east across the central Great Lakes this morning bringing scattered showers, a few embedded thunderstorms, and some areas of fog. Winds shift to northwest as it departs, peaking at around 15 to 20 knots this afternoon. Conditions dry out as high pressure builds into the area today and takes residence through Monday and into Tuesday, maintaining light winds and waves. A more active weather pattern follows beginning late Tuesday as the next low pressure system sends a warm front across the region. This system brings a period of numerous showers and storms Tuesday night through early Wednesday with another system likely to follow for Thursday. At this time winds are likely to remain below marine headline criteria. && .PREV DISCUSSION... Issued at 1203 AM EDT Sun May 5 2024 AVIATION... A slot of clear sky over a cool and moist boundary layer has a wide range of aviation conditions in place to begin the late night period. This favors expansion of IFR stratus and fog ahead of a cold front moving in from western Lower Mi. The front brings a weakening band of showers with the chance of a thunderstorm holding on this far east. The rain pattern breaks up with eastward extent while IFR ceiling hold on for a few hours post front. Ceiling then follows a standard daytime improvement as cooler north wind gains traction into the afternoon. For DTW/D21 Convection... Rapidly waning instability is a limiting factor for thunderstorms during the late night, although a rumble of thunder remains possible as a cold front enters the region and moves eastward shortly after sunrise. Thunderstorms are not expected after mid morning as the front exits into Ontario. DTW THRESHOLD PROBABILITIES... * Low for thunderstorms late tonight. * High for ceiling 5000 feet or less tonight through mid afternoon. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...SC MARINE.......TF AVIATION.....BT You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.