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174
FXUS63 KDTX 232312
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
712 PM EDT Wed Aug 23 2017

.AVIATION...

Light winds and mostly clear skies expected this evening into
tonight with the loss of daytime heating. There is low chance for
radiation fog developing across northern taf sites tonight and/or
MVFR stratus developing off Lake Huron, but will maintain just a
scattered wording for now. Otherwise, increasing high clouds toward
morning expected to help mitigate fog potential at TAF sites, but
FNT and PTK stand the best chance of seeing a VSBY restriction.
A solid mid deck of clouds should be around during the morning
hours, with some cu up around 5000 feet by afternoon, with isolated
showers possible once again, mainly across Thumb region.

//DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 feet tomorrow afternoon.

&&

.PREV DISCUSSION...
Issued at 355 PM EDT Wed Aug 23 2017

DISCUSSION...

Quiet stretch of weather at least through the weekend as expansive
area of high pressure tracks across Ontario and the northern Great
Lakes before stalling slightly over Quebec and the NE conus for a
couple more days. Positioning of the high will send steady feed of
cool and dry air into the region. This will result in temperatures
remaining a few degrees below normal for the coming week. Normal
highs are around 80 and lows are around 60.

The mid levels are a bit more exciting with a compact vort max
diving through southern MI Thursday. This wave is the next trough to
rotate around the dominate upper level low lifting NE out of western
Quebec. This wave will increase cloud cover over SE MI Thursday
morning with a small chance of seeing some isolated showers in the
afternoon. The early morning clouds may prevent any shallow fog from
developing. Moisture depth is thin with PWATs only around a half
inch. Better chance of precip will occur across the eastern Thumb as
northern flow behind the trough axis excites lake effect clouds and
possibly some showers as cool air advects over the warm lake.

After Thursday the high will take a firm grasp over the area with a
mid level shortwave ridge working into the Great Lakes. Upper level
flow becomes very weak across much of the country as strong
westerlies emerge across Canada. This is where model solutions start
to diverge. A mid level wave will cut off over the Midwest and try
to drift into the state but may take a few days with no steering
flow. One thing to watch will be remnants of the developing tropical
system Harvey over the western Gulf of Mexico. Airmass will be quiet
dry early next week when the trough tries to drift across lower MI,
but if the system finds itself a bit further north and east after
making landfall, the trough may be able to tap into it for moisture.

MARINE...

The pressure gradient is forecasted to weaken considerably tonight
in response to surface high pressure finally building into the
central Great Lakes. Northwest winds tonight are expected to ease
into the 15 to 20 knot range. A secondary cold front structure is
expected to push southward and release off of Lake Huron during the
day on Thursday. Winds are forecasted to veer to the northeast
during the afternoon and range between 10 and 15 knots. Cooler air
and lift along ahead of this boundary may create a favorable
environment for waterspouts, especially where any land breeze
development is possible. High pressure will eventually settle
overhead by Friday, bringing enough dry air to inhibit cloud
formation and produce favorable wind and wave conditions through the
weekend.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....SF
DISCUSSION...DRK
MARINE.......CB


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