Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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848 FXUS63 KDTX 060341 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1141 PM EDT Wed Jun 5 2024 .KEY MESSAGES... - Pattern shift for the latter half of the week brings below normal temperatures through at least the end of the week along with periodic chances of rain. && .AVIATION... An upper level low pressure system will expand across the northern Great Lakes Thursday. An upper level short wave preceding this system will advance across Se Mi late tonight/early Thurs morning. Weak elevated instability along this wave will provide a chance for thunderstorms or an isolated thunderstorm, mainly in the 07Z to 12Z time frame. Ongoing low level dry air advection will keep cloud bases relatively high, VFR. The low will sustain a strong westerly gradient across the southern lakes. This along with the growth of the daytime mixed layer will support gusty winds during the afternoon, with peak gusts around 30 knots possible. For DTW/D21 Convection...Any thunderstorm activity arriving late tonight is expected to be isolated at best. DTW THRESHOLD PROBABILITIES... * Low in crosswind thresholds being exceeded Thursday afternoon. && .PREV DISCUSSION... Issued at 324 PM EDT Wed Jun 5 2024 DISCUSSION... Showers and thunderstorms have blossomed this afternoon over southeast Michigan, and are tracking through a touch faster than most hires solutions. Surface dew pts mostly in the 68-70 degree range with MLcapes 1000-1500 J/kg per SPC mesoscale analysis. Better shear (~35 knots effective shear) attempting to catch up to continue to support isolated marginally severe storms. Regardless, some storms will be strong producing wet micro-burst winds of 50+ mph. Pronounced mid level dry slot arrives early this evening, ending shower/thunderstorm activity (23-2z), with 850 MB Theta-E dropping close to 20 K. Mid level cold pool (-22 C at 500 MB) will be pushing into northern lower Michigan by Thursday morning, and lapse rates look to be quickly steepening up with a narrowing moisture plume streaming in from the Midwest, generating some modest cape in the mid levels. Expecting scattered showers/isolated thunderstorms as showalter index reaches at or slightly below zero. Yet another mid level dry slot moving through during the afternoon hours, making activity difficult with limited coverage at best. Increased mixing depths expected to product breezy conditions, with westerly wind gusts aoa 30 mph. 850 MB temps progged to bottom out in the mid single numbers Friday morning, but with the slow movement of the large 500 MB low exiting the northern/eastern Great Lakes, still probably enough marginal instability to produce isolated-scattered shower activity, especially over the Thumb region. Short lived confluent upper level flow/shortwave ridging for the first half of the weekend, before yet another upper level wave/re- enforcing cold shot arrives for the second half of the weekend. 850 MB temps forecasted to bottom our in the 3-5 C range Monday morning. Another upper level ridge, a bit more pronounced, is then expected to build in for Tuesday, supporting temps slightly above normal. MARINE... The ongoing passage of a cold front will bring a line of showers and thunderstorms across the Great Lakes through the afternoon and evening. Some isolated development ahead of this main line is possible. There will be a marginal risk for severe weather across all of the eastern Great Lakes given the building instability, where wind gusts in excess of 30 knots and hail to an inch will the most likely hazards with the strongest storms. While much less likely, an isolated waterspout cannot be ruled out with the thunderstorms. Passage of the front will veer wind direction from the southeast to the southwest. A cooler air mass will then gradually setup over the Great Lakes into the end of the week. The enhanced mixing depths will bring some breezy conditions, particularly for the nearshore zones. A Small Craft Advisory has been issued for the Saginaw Bay tomorrow as a smaller window for southwest fetch will enhance wind gusts potential to around 25 knots, which would produce wave heights to or in excess of three feet. Wind speed and gust potential will then reduce in magnitude overnight. HYDROLOGY... Showers and thunderstorms around this afternoon will taper off early this evening. The airmass is seasonably warm and moist. Thus storms are efficient rain makers with widespread rainfall amounts up to half inch expected. Localized higher amounts are possible in the stronger thunderstorms, with potential storm total rainfall amounts in the 1 to 2 inch range. Minor flooding of prone urban and low-lying areas, ponding of water on roadways, and rises in area rivers will all be possible. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Small Craft Advisory from 10 AM to 10 PM EDT Thursday for LHZ421- 422. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....SC DISCUSSION...SF MARINE.......AM HYDROLOGY....SF You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.