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Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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722 FXUS63 KDTX 242004 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 404 PM EDT Mon Jun 24 2024 .KEY MESSAGES... - A complex of showers and thunderstorms arrive early Tuesday morning bringing a low potential for an isolated strong to possibly severe wind gust. Locally heavy rainfall is also possible. - An additional round of thunderstorms is possible Tuesday night into early Wednesday, mainly along and south of the I-94 corridor across Washtenaw and Wayne County. - Cooler and less humid air moves back into the area late Wednesday and lasts through Thursday. && .DISCUSSION... Nearly full insolation this afternoon with a high pressure and shortwave ridge moving through has allowed temperatures this afternoon to climb mostly into the upper 70s and low 80s. The lower humidity with dewpoints mostly in the lower to mid 60s should make for a relatively pleasant evening free of any precipitation. Temperatures tonight expected to fall into the 60s. Attention turns toward the Upper Midwest tonight and the expectation for upscale growth across Wisconsin. This system will be triggered by a northern plains shortwave and move along a warm front. Initiation will be near the triple point with a strong low level jet of 50+ knots driving this MCS east/southeast. There still remains some differences in the CAMs as to where the strongest portion of this line sets up and moves into portions of western Michigan. Greater consensus would be towards Chicago closer to the thermal gradient. In any case, any northward extension of this system will encounter a stable surface layer as it arrives into southeast Michigan. There will be elevated instability to work with being directed into the area via the strong low level jet, which will support numerous to widespread coverage of thunderstorms spreading across the area. Timing has activity reaching western portions of the CWA between 09-11Z while continuing to weaken and push east before 16Z with potentially trailing isolated to scattered showers for the early portion of the afternoon. An outlook of general thunderstorms is in place prior to 12Z tomorrow. A Marginal Risk is in place for all of southeast Michigan post 12Z, which would cover the bulk of these morning thunderstorms. While expectation is for this MCS to be weakening, there remains at least a low probability for an isolated strong to possibly severe wind gust as this system rolls through. The greater surface moisture with the warm sector arrives Tuesday afternoon in the wake of the early morning system with dewpoints returning to the 70s. This will yield strong afternoon instability, but indications are that there will be a strong cap in place for the afternoon greatly limiting any the potential for thunderstorms. Have cut back on PoPs from previous cycle for tomorrow afternoon given this trend, but will continue to monitor how things evolve post morning convection. The best instability with the frontal boundary then sets up along the southern Michigan border along with any potential outflow boundary late in the day. This will be the focus for potential evening and overnight convection as lower level jet ramps up again. Strongest activity looks to hold south of the state, with uncertainty as to how far north any activity develops. Low end PoPs will extend up through I-69 corridor, but greatest chance for thunderstorms will reside along and south of I-94. This activity could again pose a Marginal Risk for severe weather if it materializes. The next trough and cold front dropping out of the western/northern Great Lakes arrives Wednesday morning and sweeps through during the afternoon. This will keep chances for showers and weak thunderstorms into Wednesday afternoon until the front pushes completely through. High pressure is then expected to quickly build in Wednesday evening through Thursday bringing with it dry and slightly temperatures into the 70s for Thursday. Another shortwave and surface low is forecast to organize over the plains and continue through the Midwest bring the next chance of showers and thunderstorms on Friday. && .MARINE... High pressure holds directly overhead through this evening maintaining light winds and minimal waves across the region. This high eventually drifts off to the east overnight as low pressure strengthens over the upper Midwest/northern Ontario. This low is expected to result in a thunderstorm complex (a MCS) forming over Wisconsin before rapidly moving into the Great Lakes late tonight into Tuesday morning. Exact track this complex takes still carries a bit of uncertainty though models are generally favoring it to dive towards southern Lake Michigan resulting in a glancing shot of showers and decaying thunderstorms for the central Great Lakes. A few strong wind gusts will be possible within these storms. Breezy southwest winds develop daytime Tuesday in advance of an approaching cold front warranting the need for Small Craft Advisories for all nearshore waters. Front gradually sags through the area offering some potential (~20-30%) for additional showers and storms Tuesday evening into early Wednesday morning- mainly focused over the southern Great Lakes. && .HYDROLOGY... An active pattern of thunderstorms returns to Lower Michigan by early Tuesday morning as warm and humid air surges back into the region. Most of southeast Michigan will see at least a period of showers during the morning as thunderstorms decrease intensity while moving through. Rainfall totals average 0.25 to 0.50 inch. The Tuesday morning activity is followed by a break in the afternoon until the next round of storms becomes possible Tuesday night into Wednesday morning. Current forecast trends suggest the best thunderstorm potential along and south of I-94. Additional totals of 0.25 to 0.50 inch with up to 1 inch are possible with this activity until it exits the area by Wednesday afternoon. The potential for flooding in each event is greater where repeated rounds of storms occur over the same area making ponding of water on roads and in prone low lying areas possible. The Tuesday and Wednesday activity collectively could lead to a brief response in the level of streams and rivers across the area. && .PREV DISCUSSION... Issued at 152 PM EDT Mon Jun 24 2024 AVIATION... High pressure maintains dry and VFR conditions this evening with weak and variable winds organizing out of the south to southwest tonight in response to an approaching frontal system from the upper Midwest. Mid/high clouds will increase overnight ahead of this system but will remain VFR. Confidence is increasing on a thunderstorm complex to emerge from the system and track eastward into the area Tuesday morning. Instability will be weak this far east, so expect the storms to be elevated and weakening as they move through mainly between 10z and 15z. The main impacts will be lowered visibility in heavy downpours and an isolated strong wind gust. Warmer air arrives on a breezy southwest wind Tuesday afternoon with a slight chance for additional convection to develop as the cold front moves through late. For DTW/D21 Convection...Adjusted the Tuesday morning TSRA window an hour earlier to 13-16z based on latest hi-res trends. Considered adding a PROB30 TS mention for potential late Tuesday afternoon convective redevelopment but confidence remains too low with model soundings showing stability/capping concerns. DTW THRESHOLD PROBABILITIES... * Medium for ceilings aob 5kft Tuesday after after 12z. * Medium in thunderstorms Tuesday morning mainly 13-16z. Low confidence late Tuesday afternoon. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Small Craft Advisory from 5 AM to 10 PM EDT Tuesday for LHZ421-422- 441>443. Lake St Clair...Small Craft Advisory from 8 AM to 4 PM EDT Tuesday for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory from 8 AM to 4 PM EDT Tuesday for LEZ444. && $$ DISCUSSION...AA MARINE.......KDK HYDROLOGY....AA AVIATION.....TF You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.