FXUS63 KDTX 181758 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 158 PM EDT Mon May 18 2026 .KEY MESSAGES... - Warm and humid conditions exist today and Tuesday which support the risk of severe thunderstorms each day, mainly during the afternoon and evening hours. The strongest storms are capable of damaging wind, large hail, and isolated tornadoes. - A cold front Tuesday night ushers in dry and cooler weather for Wednesday and Thursday. - The next chance of rain arrives Friday and Friday night. && .AVIATION... Conditions deteriorate this afternoon and evening as a line of strong to severe thunderstorms moves through the airspace. VFR ceilings and visibilities drop sharply along the interface of the convective line with temporary IFR conditions likely. Upstream observations and local storm reports indicate gusts in excess of 70 mph are possible with this organized line. Current trajectories reveal storm motion of approximately 45 mph, forecast to move through the terminals between 20Z and 23Z. A conditionally unstable airmass is allowing for a few pre-trough storms to develop ahead of the line with low confidence that these storms survive across the airfields. However, did move up the TEMPO period for the Metro terminals to account for the possibility of slightly earlier discrete activity. Limited model signal for widespread redevelopment late this evening behind the line, although better chances exist at MBS. Winds decrease slightly overnight, holding from the southwest into Tuesday with a mainly dry start and D21/DTW Convection...Most likely time-frame for thunder will be from 20-22Z. A period of IFR visibility will accompany the line of storms. Potential for additional thunderstorms has decreased for Tuesday afternoon/evening, but a chance remains. .DTW THRESHOLD PROBABILITIES... * High for thunderstorms this afternoon and early evening, then low- medium for thunderstorms Tuesday afternoon/evening. * Medium for ceilings at or below 5000 ft with thunderstorms this afternoon and evening. && .PREV DISCUSSION... Issued at 1148 AM EDT Mon May 18 2026 UPDATE... The setup for severe thunderstorms remains favorable for SE Mi this afternoon and evening with the primary hazard being damaging wind gusts. Instability trends are certainly on track as full morning sun has already lifted temperatures into the lower 80s all areas with a few mid 80s reported leading up to the noon hour. The 12Z DTX sounding is also capped around 750 mb, enough to allow buildup of but easily eroded by the inbound MCV. Model MLCAPE forecasts up around 2000 J/kg in HREF mean and RAP projections are then within reach by mid afternoon to establish a receptive downstream environment for the ongoing convective complex as it moves NE into the area. The system is already demonstrating benefits of the locally enhanced wind shear profile supplied by the parent MCV resulting in a mature linear convective mode, however this is where the most uncertainty lies in terms of downstream persistence. Model projections really struggle to maintain 0-6 km bulk shear above 25 knots which suggests the system enters SE Mi near full strength but is open to gusting out at some point while crossing SE Mi and exiting into Lake Huron and Ontario by early evening. PREV DISCUSSION... Issued at 307 AM EDT Mon May 18 2026 DISCUSSION... Warm frontal boundary responsible for the prolific hail producing supercellular activity across portions of the Saginaw valley and northern thumb late Sunday will finally ease north of the region this morning as higher magnitude warmth increases influence within deepening southerly flow. Benign conditions ensured thru late morning as stability holds under modest capping. Influx of higher quality moisture will commence during this time, establishing a notable moisture gradient from west to east by early afternoon /dewpoint of mid 60s west to upper 50s east/. This affords a moderate level of diurnal boundary layer destabilization for at least western sections. Given an afternoon temperature of middle 80s, mlcape projection of upwards of 1500-2000 j/kg will peak across the Saginaw valley and down through the Highway 23 corridor. This leaves a receptive downstream environment for potential reorganization/ expansion of any MCV governed remnant nocturnal convective activity spilling downstream. A fairly strong model consensus exists on this scenario, targeting lower Michigan for a mid-late afternoon increase in coverage. A broader threat window locally between 19z and 01z with dependence on pace of the MCV. The background wind field remains modest, but subject to a localized meaningful increase both across the lower levels and with greater depth as the feature moves through. Supportive environment to offer a risk of both large hail and damaging wind gusts, with greater overall potential with westward extent. A focused area of higher SRH does materialize as low level flow backs briefly with a slight shift in the pressure gradient orientation. Therefore, cannot completely discount the possibility for a more organized, rotating updraft to present a brief, isolated tornado threat. Outside of the convective window, forecast continues to highlight gusty southerly conditions reaching 30 to 35 mph at times today. The seasonably warm and humid conditions will exist again Tuesday ahead of a cold front. A more muddled early day picture in terms of both cloud cover and precipitation chances, as a portion of the model solution space suggest possible activity prior to 18z owing to some combination of the ongoing moisture advection and remnant midwest convection leftover from tonight. Degree and pace of destabilization certainly still subject to change. Assumption for at least a weakly unstable environment timed favorably with an evening cold frontal passage will present an opportunity for deeper updrafts to organize within a sufficient background deep layer wind field along the frontal zone. The SPC Day 2 outlook maintains a slight risk designation to highlight the associated strong wind and large hail threat for the late Tuesday period. Warm sector environment will again become diurnally gusty, with winds reaching 30 to 35 mph from the south at times. Notably cooler post-frontal environment arrives Wednesday. This will occur with the backdrop of increasing low to mid level ridging, ensuring a stretch of dry and stable conditions lasting into Thursday. Low level thermal trough marked by 850 mb temperatures of lower single digits, lending to below average readings during this time. Coldest conditions Thursday morning as the surface high centers locally - lows dipping into the 30s in some locations. Dry conditions likely to hold under a modest warming trend Friday, as the next system organizes upstream. This system will introduce the next chance of rain Friday night into Saturday. MARINE... A warm front releases north across Lake Huron this morning, with southerly winds expanding across all local waters. Strong low level jet winds will struggle to mix down over the open waters where cool water temperatures maintain stable over-lake conditions. Gusty southwest flow will thus be confined to the nearshore waters, aided by warmer water temperatures and land influence. Frequent gusts today and Tuesday are expected to hold between 25 and 30 knots, but an isolated gust to 35 knots over Saginaw Bay cannot be entirely ruled out. Small Craft Advisories are in effect for today and will be needed Tuesday as well. More localized wind/wave impacts arrive with thunderstorm activity this afternoon-evening, and again Tuesday when a cold front sweeps through the area. There is potential for some of these storms to be strong to severe with all modes of severe weather in play. The cold front comes through Tuesday night, followed by high pressure filling in mid-week to support a quieter and more seasonable late May pattern. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422- 441>443. Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460. Michigan waters of Lake Erie...None. && $$ AVIATION.....KGK UPDATE.......BT DISCUSSION...MR MARINE.......MR You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.