Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 180743 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 343 AM EDT Fri Aug 18 2017 .DISCUSSION...
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Low pressure centered over eastern Lake Superior is sweeping a cold front through Lower Michigan during the early morning. The front and associated clusters of showers will be east of the region shortly after sunrise leaving cloudy but dry conditions in place across SE Michigan during the remainder of the morning. The passage of the front will bring cooler and less humid air into the region as surface dewpoint settles into the 60-65 degree range compared to lower 70s yesterday. Most of the postfrontal low level cold advection will be complete by late morning which, along with lingering cyclonic low level flow, will support broad coverage of stratus/stratocu into early afternoon. Decreasing clouds mid to late afternoon is expected to occur first in the Detroit area as the low level thermal trough follows the low pressure center to the north and east. Highs around 80 will then be possible with a late boost of sun while readings linger in the mid 70s for the Tri Cities and northern Thumb. The gradient trailing the low pressure system will also support breezy conditions with gusts approaching 30 mph as boundary layer mixing builds through the day. The decreasing cloud trend will continue into the evening but will be short lived as the next upper wave approaches from the Midwest. This system is observed over the Plains states this morning and appears plenty strong enough to support model solutions that indicate the wave sharpening as it enters the long wave trough over the Great Lakes tonight. The surface pressure reflection is shown to be weak and well south of the Ohio border compared to the upper level features. The farther south position looks Ok but the surface wave could end up deeper as it interacts with the remnant baroclinic zone in the Ohio Valley. Backed and slightly stronger low level flow will then begin northward moisture transport that will be greatest closer to the surface wave. This is where convective potential will be better while higher based theta-e advection spreads clouds over Lower Michigan with a chance of showers after midnight through Saturday morning. The upper level short wave exiting Saturday morning will propel the long wave trough axis into the eastern Great Lakes Saturday afternoon. Subsident northwest flow aloft and building surface high pressure will produce dry conditions Saturday night through Sunday. This will be part of a quick transition into a more zonal large scale upper air configuration heading into next week. Expect temperatures to return well into the mid and upper 80s by Monday as surface high pressure shifts toward the Atlantic coast. Global model solutions then project the next wave aloft already developing over the Great Lakes by Tuesday. The low pressure system and associated front will bring the greatest probability of rain Tuesday into Tuesday night followed by a modest cooling trend for the second half of next week.
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&& .MARINE...
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A fresh southwest breeze is developing over the waters this morning as cooler air moves into the area. Cold air in the wake of the cold front is boosting the over-lake instability profile and will support wind gusts around 25 knots. Elevated wind gusts to 30 knots are possible in as the flow funnels through Saginaw Bay. Maximum wave heights around 7 feet are likely in outer Saginaw Bay and the tip of the Thumb. Otherwise the offshore fetch will contain the highest waves to central and northern Lake Huron. Wind and waves will then decrease over the weekend as high pressure builds into the Great Lakes region.
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&& .PREV DISCUSSION...
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Issued at 1059 PM EDT Thu Aug 17 2017 AVIATION... Stratus will filter into area within southwest flow around low pressure crossing through the northern Great Lakes. Expect MVFR cigs late tonight through a good part of Friday with a trend late back to VFR and eventually some clearing. These southwest winds will be a bit gusty from mid/late Friday morning through the afternoon with gusts into the 22-26 knot range. Wind direction will also veer to a more westerly direction during the afternoon. For DTW...Expect generally VFR stratus to work into area tonight, but some potential of MVFR late at night. These conditions will hold on Friday with improvement back to VFR from afternoon into evening. Wind gusts to 25 knots will be possible from 240-250 degrees. //DTW THRESHOLD PROBABILITIES... * High in ceilings AOB 5000 ft late tonight into Friday afternoon.
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&& .DTX WATCHES/WARNINGS/ADVISORIES...
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MI...NONE. Lake Huron...Small Craft Advisory from noon today to 8 PM EDT this evening for LHZ443. Small Craft Advisory until 8 PM EDT this evening for LHZ421-422-441- 442. Lake St Clair...Small Craft Advisory from noon today to 8 PM EDT this evening for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory from noon today to 8 PM EDT this evening for LEZ444.
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&& $$ DISCUSSION...BT MARINE.......JVC AVIATION.....DG You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.

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