Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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767
FXUS63 KDTX 311048
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
648 AM EDT WED AUG 31 2016


.AVIATION...

The surface cold front will slide across metro Detroit between 12Z
and 15Z. Its progress will then slow as it advances southeast of DTW
this afternoon. Post frontal northerly winds will lead to a steady
advection of drier air into the boundary layer during the course of
the day. The high amount of low level moisture has led to the
development of pockets of IFR stratus in the vicinity of the front.
Ceilings heights will rise, generally from north to south, during
the course of the morning and early afternoon. However, there is
expected to be considerable variability in cigs throughout this
period.

For DTW...Daytime heating will lead to the development of some
afternoon thunderstorms along the front. Again this will be
southeast of DTW, but likely still in the southern portions of the
D21 airspace. There will be an increase in the post frontal NNW
winds this afternoon as daytime heating deepens the boundary layer.
The closer proximity to the frontal boundary suggests lower clouds
will persist at metro well into the afternoon.

//DTW Threshold Probabilities...

* Moderate in ceilings below 5000 feet this morning and afternoon.

&&

.PREV DISCUSSION...
Issued at 315 AM EDT Wed AUG 31 2016

DISCUSSION...

Deep moisture axis (PW values up to 2 inches) early this morning
ahead of the weak cold front has been sufficient to generate
numerous showers/isolated thunderstorms in the M-59/I-69 corridors
with some right entrance forcing, which will be ending shortly, and
thus expecting majority of the activity to be over around 12z.
Still, quick diurnal boost in instability toward the Ohio border by
Noon could allow for another brief flare up of activity, before
surface front sinks south of the border and much drier air takes
hold.

Steady stream of cold advection to take place over the next 36-48
hours as winds become north and then northeast over the Central
Great Lakes. Upper level circulation over James Bay Early this
morning, with an additional upper level energy/cold pool over
Northern Manitoba, which will race south through Lower Michigan
Tonight/Thursday. 00z Raob out of Pickle Lake indicating 0 c at 700
mb with good momentum, 25 knot northwest winds. With this amount of
cold air (850 mb temps 7 C) coming over warm waters of Lake Huron,
still expecting some light shower activity to be generated, which
will probably push farther inland during Thursday (see 00z euro/gfs)
as low level winds become northeast and low level lapse rates
steepen up, with 50-100 J/kg of cape generated in the 5-10 kft
layer. At very least, would expect skies to become mostly cloudy
during Thursday, holding maxes in the low to mid 70s. Despite the
strong upper level ridge axis building into the Great Lakes Region
on Friday, looking at similar maxes on Friday, due to the cool start
and limited mixing with the surface high established over northern
Lower Michigan/Lake Huron. Also, with the northeast flow off Lake
Huron providing some moisture flux, would expect a solid cu up
during the day.

Abundant sunshine over the weekend, as 588-590 DAM ridge center at
500 MB progged to be situated over the Central Great Lakes both
Saturday and now Sunday (per 00z Euro/Canadian). Return flow around
the surface high on Sunday should be able to yield maxes above at or
above 80 degrees as 925 mb temps reach 20 C or slightly better (per
euro).

MARINE...

A cold front will continue on a southward track across srn Lower Mi
this morning before settling into nrn Ohio this afternoon. Post
frontal northwest winds will increase across Lake Huron throughout
the day as colder air advects across the lake. Gusts over the
southern half of the lake will likely reach 20 knots by afternoon. A
reinforcing shot of cold air will arrive tonight under strengthening
northerly winds. The winds will increase on Lakes St Clair and Erie
in addition to Lake Huron. These gusty winds will persist through
the day Thursday. There is a high probability that wind gusts in the
tonight through Thurs evening period will range from 25 to 30 knots
across srn Lake Huron. This will lead to rather treacherous
conditions for small craft. The depth of the cold air over the lake
combined with relatively warm lake temperatures will also be
supportive of waterspout development late today through Thursday
night. Winds are forecast to veer toward the northeast late Thurs
into Thurs night. High pressure will be slow to build into the
region from the north late in the week. So the decrease in wind
speeds will be very gradual Thurs night through Friday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 8 AM to 10 PM EDT Thursday FOR LHZ442-443.

     Small Craft Advisory from 10 PM this evening to 10 PM EDT Thursday
     FOR LHZ421-441.

Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....SC
DISCUSSION...SF
MARINE.......SC


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at www.weather.gov/detroit.



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