Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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073 FXUS63 KDTX 281911 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 311 PM EDT Fri Jul 28 2017 .DISCUSSION... As of 18Z, the center of a compact upper low was located just east of Lansing. It is still forecast to track across the southern portions of metro Detroit around 21Z. There has been some noted enhancement in the cu field across metro Detroit and points south, with some isoated shower development. An axis of instability (0-1km MLCAPE of 500 to 800 J/KG) along and south of a Howell to Detroit line will continue to warrant a low chance of a late afternoon shower or thunderstorm. Strong subsidence and low to mid level drying will then overspread the remainder of the forecast area this evening, ending the risk for convection and scouring out any lingering cloud cover. The loss of daytime heating this evening will lead to a decrease in the northeast winds. It will take a slight weakening in the gradient later in the night for some drop in the northeast winds off the relatively warm waters of Lake Huron. Water levels at Essexville have been holding steady around 48 inches above chart datum this afternoon, which is the threshold at which minore flooding impacts the shoreline in Bay County. Water levels will likely drop a little more later this evening as winds begin to decrease. Amplification of a mid level ridge across the northern Great Lakes tonight into Saturday will force sfc high pressure into Lower Mi. This sfc high will then influence the region through the weekend. The ongoing dry air advection under the north-northeast gradient will persist into Saturday. Decent daytime mixing heights will support daytime highs near 80 away from Lake Huron on Saturday. Some airmass modification, continued good mixing depths under full sun and a loss of the flow off Lake Huron will push highs into the 80s on Sunday. The weak gradient and dry airmass will support decent radiational cooling, with temps dropping into the 50s Sat night. A broad region of high pressure will remain over the region early next week as shortwave ridging keeps dry conditions in place through Tuesday. Gradual air mass moderation Monday into Tuesday will allow highs to increase into the mid 80s and lows into the 60s. Low pressure tracking east through central Canada will bring a cold front across Lower Michigan during the Wednesday-Thursday timeframe as an amplifying trough digs into the region. The next chance for showers and thunderstorms will accompany the frontal passage before highs return to the upper 70s late next week. && .MARINE... Maximum wave heights of 6 to 8 feet will continue into the first half of the night along the exposed nearshore waters of the Thumb as fresh onshore flow persists. High pressure will build in late tonight and promote tranquil conditions for the remainder of the forecast period. && .PREV DISCUSSION... Issued at 1231 PM EDT Fri Jul 28 2017 AVIATION... Northeast flow prevails as high pressure builds in from the northwest immediately behind the passing low presently located directly overhead. Corridor of increased ascent easily identified on visible as widespread CU below 5kft. A few showers will be possible in the Detroit area as this activity pushes south and east over the next several hours. Otherwise, expect clouds to dissipate giving way to SKC overnight. For DTW...Prevailing wind out of the NE quadrant will favor NE operations through the forecast period. //DTW THRESHOLD PROBABILITIES... * High for cigs aob 5kft && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Advisory until 11 PM EDT this evening for MIZ048. Beach Hazards Statement until 10 PM EDT this evening for MIZ049-055- 063-083. Lake Huron...Small Craft Advisory until 4 AM EDT Saturday for LHZ421-422-441>443. Lake St Clair...Small Craft Advisory until midnight EDT tonight for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory until 4 AM EDT Saturday for LEZ444. && $$ DISCUSSION...SC/JD MARINE.......JVC AVIATION.....JVC You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.

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