Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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813 FXUS63 KDTX 112305 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 705 PM EDT Tue Jun 11 2024 .KEY MESSAGES... - Warming trend through mid-week with high temperatures possibly reaching 90 degrees Thursday. - The next chance for rain and thunderstorms will also be Thursday. Isolated strong to severe thunderstorms will be possible with a Marginal Risk in place across much of southeast Michigan. - Higher than usual confidence in hot and humid conditions early next week. Temperatures into the 90s Monday and Tuesday with relatively high humidity will likely bring the highest heat indices we have seen so far this year. && .AVIATION... High pressure exits toward the Atlantic coast while the next Midwest frontal system approaches Lower Mi tonight. Increasing high clouds this evening are the first sign of moisture along and ahead of the front, beginning as a ceiling of cirrus and then dropping late tonight while remaining above 5000 ft. There will also be some virga indications from radar and possibly a stray sprinkle reaching the ground through early morning. The cold front weakens but still remains the focus of cumulus enhancement while moving west to east across Lower Mi Wednesday afternoon. The cumulus cloud component contributes to broken ceiling around 5000 ft into Wednesday evening. For DTW/D21 Convection...Thunderstorms are not expected tonight and Wednesday. DTW THRESHOLD PROBABILITIES... * Moderate for ceiling aob 5000 feet Wednesday afternoon. && .PREV DISCUSSION... Issued at 341 PM EDT Tue Jun 11 2024 DISCUSSION... Lake aggregate stable high pressure parked over the Central Great Lakes this afternoon will maintain a predominate dry southeasterly flow influence through tonight. Very pleasant and comfortable weather is in store through this evening with temperatures falling back into the 60s after sundown. The next upper level jet packet (exit region) will push into the western Great Lakes late tonight touching off the lead edge of warm advection. Models resolve a fairly abrupt bout of 850-650mb thetae return prior to 12Z Wednesday, however, organization to any warm front structure is poorly defined. A high based sprinkle will certainly be possible the latter half of tonight with some help from cloud top cooling, but confidence is too low to include. A modest boost in surface dewpoints into the middle to upper 50s will yield warmer conditions Wednesday afternoon. Heat indices are forecasted to be well into the lower 80s. The southern edge of a deep midlevel trough will force a cold front through Southeast Michigan during the late afternoon and evening hours on Thursday. Moisture return in advance of the cold front is forecasted to be disjointed with only the low level thetae content arriving in a very narrow axis from north to south after 18Z. Note any sub 700mb thetae early Thursday is positioned within the anticyclonic flow trajectories which will ensure the column starting from a baseline of high static stability in the lowest 5.0 kft agl. The modeled UVV signal suggests there will be two potential forcing mechanisms of interest. The first is high based convective remnants coasting into the northern forecast area from the Upper Mississippi River Valley after 09Z. Relatively high confidence exists in weak/lack of vigor to vertical motion early. The second potential forcing mechanism will be shortwave energy attendant to the anticyclonic shear side of the upper level jet that could arrive after 18Z at or around the time of the front. The details for Thursday afternoon are going to matter as some forecast data suggests that active midlevel subsidence between 4.0 and 12.0 kft will arrive coincident with increasing shear. Kinematics certainly become impressive during the afternoon with a midlevel jet exceeding 50 knots yielding 0-6km bulk shear increasing to nearly 50 knots. Hires modeled storm motion relative to the shear vector is generally parallel during the Thursday afternoon period here in Michigan with some greater updraft/shear balance potential over Ontario south of the Bruce Peninsula. MLCAPES are expected to reach 1000 J/kg so an isolated large hail/strong wind gust severe thunderstorm will be possible sometime between 18Z-00Z Thursday. The latest Swody3 has a Marginal designation for Severe Weather north of Metro Detroit. Surface high pressure and strongly anticyclonic flow trajectories are expected to result in comfortable summer weather conditions Friday and Saturday with limited humidity. Longwave ridging is then expected to amplify rapidly Sunday and early next week with H5 geopotential heights reaching above 580dam as far north as James Bay. Everything is shaping up to be a notable time period for heat by Monday as 850mb temperatures easily exceed 20C. Current forecast soundings do not show a considerable amount of midlevel warm air so there is some question to how capped off the environment will be. As a result, could see some convective complex(es) short circuit daytime heating for a day or so, but given the setup and potentially multiple days of heat it should be rather noteworthy. The current forecast has heat indices in the upper 90s next Monday and a NWS HeatRisk as a Category Red. MARINE... Tranquil weather will continue through the mid week as the ridge of high pressure continues to shift eastward. This will bring a return- flow setup, veering winds southerly as the gradient slowly becomes more established into the second half of the week. A low pressure system is projected to arrive late Thursday into Friday which could support a period of Small Craft Advisory conditions with several opportunities for showers and thunderstorms. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....BT DISCUSSION...CB MARINE.......SS/KGK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.