Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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281 FXUS63 KDTX 060750 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 350 AM EDT Thu Jun 6 2024 .KEY MESSAGES... - Morning showers and a few rumbles of thunder clear out by mid-morning with drier conditions this afternoon. - Cooler today with highs in the mid 70s. Even cooler on Friday with highs in the upper 60s. - Periodic rain chances continue Friday and into the weekend. && .DISCUSSION... A pattern shift is underway today, evident via local mid-level height falls of 5.0-7.0 dam over the past 12 hours owing to the expansion of a deep upper low that is centered over Manitoba. As this low expands overhead, several shortwaves will ripple through the longer wavelength trough between today and Friday. The first of these waves has caught up to a low level theta-e axis, which is driving a cluster of showers and a few rumbles of thunder across much of SE Michigan this morning. Best coverage throughout the morning will be favored toward the Tri Cities and Thumb in closer proximity to the height fall center, while areas near the Ohio border may see little to no rain at all. Overwhelming consensus among the guidance is to push the wave into Ontario by mid-morning, before boundary layer destabilization can occur. Considering a strong backdrop of Dcva and dry advection in the low levels, conditions dry out for all of SE Michigan. Healthy coverage of diurnal cumulus is then expected to develop by afternoon, although should not have too strong of an impact on deep boundary layer mixing. Breezy conditions thus are able to develop this afternoon with gusts of generally 25 to 30 mph. The depth of the mixed layer squeezes out high temperatures in the mid 70s, even with the onslaught of cold advection. By this evening, the upper low will have made significant southeastward progress into northern lower Michigan. This will wrap a more cohesive stream of moisture into the Tri Cities and Thumb, leading to isolated to scattered shower development as MUCAPE rebounds to a few hundred J/kg. Equilibrium levels at best reach -10 C, limiting thunder chances both tonight and Friday. A showery day is in store for Friday as cold advection ramps up. H8 temperatures of +3 C to +5 C moving across warm Lake Michigan waters (+16 C) will trigger a lake response to support scattered showers and stratocu that will stream into SE Michigan. This will be the coolest day of the forecast period, with daytime highs sticking in the mid to upper 60s. Expansive troughing patterns holds in place over Canada for several days, with dual upper lows developing by the weekend. This maintains an active jet across the northern part of CONUS, including lower Michigan, which will direct additional shortwaves into SE Michigan through the weekend. This is likely to result in dry periods and unsettled periods throughout the weekend. Daytime highs will fall a few degrees short of normal, in the low to mid 70s for Saturday and Sunday. Ensemble mean 500mb heights do not show a breakdown in the troughing pattern until middle of next week, so additional precipitation chances are likely to evolve through then. && .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. && .PREV DISCUSSION... Issued at 1141 PM EDT Wed Jun 5 2024 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. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Small Craft Advisory from 2 PM this afternoon to 10 PM EDT this evening for LHZ441>443. Small Craft Advisory from 10 AM this morning to 10 PM EDT this evening for LHZ421-422. Lake St Clair...Small Craft Advisory from 2 PM this afternoon to 10 PM EDT this evening for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory from 2 PM this afternoon to 10 PM EDT this evening for LEZ444. && $$ DISCUSSION...MV MARINE.......AM AVIATION.....SC You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.