FXUS63 KDTX 191804 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 204 PM EDT Tue May 19 2026 .KEY MESSAGES... - Scattered severe thunderstorms remain possible through early evening. - Dry and cool Wednesday through Friday morning. - Rain returns by Friday evening and continues into Saturday. && .AVIATION... Another hot and humid day (by mid-May standards) lends potential for diurnal convection this afternoon and early evening. To the west of the terminals, initial updrafts are testing what little remains of the capping inversion layer, characterized by shallow updrafts and limited glaciation/lightning. Meanwhile, sufficient daytime insolation should lead to surface-based instability within the next couple of hours marking an expansion in convective coverage across some of the terminals. Confidence is highest from PTK south, but uncertainty in overall coverage/intensity of thunderstorms remains. FNT will be right on the edge of the pre-frontal troughing so opted for a VCTS mention as opposed to a TEMPO for thunder the rest of the PM hours. Visibilities will drop to IFR in the heaviest downpours. Non-convective gusts have stayed elevated given the ambient wind fields, but expect enhancements within water-loaded downdrafts. Nocturnal stabilization emerges overnight as gusts drop-off, and gradient winds gradually veer toward the north throughout the overnight hours. Post-frontal northerly flow draws a plume of low- level moisture through Southeast Michigan late tonight into Wednesday morning favoring MVFR ceilings. D21/DTW Convection...Window for scattered convection is focused between 20Z and 23Z this afternoon/evening, although initial storms could drift eastward a bit sooner. Storm motion will be southwest to northeast around 40 kt while the corridors of storms migrate west to east. IFR visibility reductions possible in heaviest downpours. .DTW THRESHOLD PROBABILITIES... * Medium for thunderstorms 20-23Z today. * Medium for ceilings at or below 5000 ft through this evening, then high early Wednesday. && .PREV DISCUSSION... Issued at 946 AM EDT Tue May 19 2026 UPDATE... No significant changes to the inherited forecast. A subtle shortwave lifting northeast out of the Western Ohio Valley is expected to provide a focus for late afternoon storm development. Unidirectional moderate southwest flow exists ahead of a cold front this afternoon with MLCAPE at or above 1500 J/kg, mainly south of I- 69. A pre-frontal surface trough should allow for renewed convective development in the uncapped environment during peak heating of the day (3-7 PM). The bulk of hi-res solutions indicate multicells becoming a scattered to broken line of convection, with good agreement on the progressive nature of the activity pushing east rather quickly. Like yesterday, localized/scattered damaging wind gusts should be the dominant hazard. However, the actual cold front will have to track through during the evening hours, and additional storms will be possible with any leftover instability. At the very least, expect scattered showers before the front clears the state and low-level dry air surges in, sending surface dew points down into the 30s/40s for Wednesday. PREV DISCUSSION... Issued at 310 AM EDT Tue May 19 2026 DISCUSSION... Higher magnitude warmth and humidity for mid May entrenched locally early this morning, as the area holds within deep layer south- southwest flow for one final day. Forecast for today offers a more muddled picture in terms of convective potential, scale and timing relative to that noted yesterday. Intermittent bouts of meaningful moisture advection will deliver another surge of higher quality theta-e early in the day, providing some potential for greater cloud cover to exist along with the possibility for some pockets of convective showers. With that, expectation for gradual boundary layer destabilization with time as intervals of greater insolation capitalize on the elevated dewpoint (mid-upper 60s), yielding upwards of 1500 j/kg of mlcape by late afternoon. There is a definitive model signal for higher instability to exist southeast of a Howell to Sandusky line, but with the best instability (2000+ j/kg of mlcape) remaining across Ohio. Convective focus most likely along some composite pre-frontal trough or remnant convective vort max out ahead of the main cold front within the 19z to 00z window, offering the greatest potential for more meaningful updrafts to emerge mainly within the aforementioned main instability gradient. Background wind field generally modest overall, but with potential again for some local enhancement should the convective response be governed by a stronger convective wave. This maintains an opportunity for organized late day convective development carrying a risk for strong winds and large hail. Afternoon temperatures peaking in the upper 80s/near 90 across portions of metro Detroit and points south and mainly mid 80s elsewhere. Warm sector environment will again become diurnally gusty, with winds reaching 30 to 35 mph from the southwest at times. A few lingering showers around early tonight as the cold front settles through the region. Otherwise, turning notably drier and cooler as the post-cold frontal environment settles into region overnight into Wednesday. Deep layer stability held within prevailing low to mid level ridging affords dry and seasonably cool conditions lasting into Thursday. A standard moderation of the existing airmass then occurs Friday under a high degree of insolation and increasing upper height field, but still lacking in meaningful warm air advection. Highs the remainder of the week mainly in the 60s. Coldest readings noted Thursday morning, reaching into the mid and upper 30s in some locations. Southern stream shortwave forecast to eject from the southern plains into the great lakes this weekend. Increasing magnitude of mid level southwest flow downstream of this wave will drive a notable surge of moisture advection directly into Lower Michigan Friday night. While some higher based light showers are possible late Friday as the column gradually saturates, the main window for widespread, meaningful rainfall will arrive Friday evening and persist overnight. Model guidance is coalescing around a broad swath of mainly stratiform rain with embedded elevated convective elements sweeping from southwest to northeast across Southeast Michigan. Precipitation may carry over into early Saturday, before chances taper off into the afternoon. Otherwise, generally seasonable conditions for the weekend period. MARINE... A warm and humid airmass over the cooler waters of the Great Lakes will support the development and expansion of dense marine fog. Sustainment of fog will be likely through the morning hours as a strong inversion holds overhead, and will likely continue to some degree through the early afternoon until a cold front mixes out the layer. As a result, a Dense Fog Advisory has been issued through the afternoon. Otherwise, calm to lighter winds hold overnight with some limited chances for isolated showers and thunderstorms. Southwest flow increases in magnitude during daylight hours tomorrow which will bring wind gusts around 20 to 25 knots through the Saginaw Bay and along the nearshore areas which have resulted in renewed Small Craft Advisories. The development of strong to severe thunderstorms will be possible again in the afternoon and evening, favored across southern Lake Huron and locations south. Wind gusts aoa 50 knots will be the primary hazard for severe weather development. Passage of the cold front will end the severe weather threat, veering winds from the southwest to northwest through the evening. High pressure builds behind the front, bringing lighter winds through the midweek period. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422- 441>443. Dense Fog Advisory until 4 PM EDT this afternoon for LHZ361>363- 462>464. Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444. && $$ AVIATION.....KGK UPDATE.......SF DISCUSSION...AM MARINE.......MR You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.