Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 211704
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
104 PM EDT SUN AUG 21 2016

.AVIATION...

Mostly cloudy skies this afternoon with cloud bases in 3-6 kft
range, as short duration showers work through southeast Michigan as
well. Very low chance of a thundestorm. Loss of daytime heating will
allow skies to clear out this evening, with another modest VFR cu up
expected tomorrow. West-Southwest winds which have been gusting
at or slightly above 20 knots will diminish by sunset.

For DTW...There is a tempo in for showers, but duration will be very
brief and mainly dry conditations expected for the afternoon with
vfr ceilings.

//DTW Threshold Probabilities...

* Medium confidence in cigs aob 5000 feet into early evening.

* Very low chance of thunderstorm late this afternoon/early evening.

&&

.PREV DISCUSSION...
Issued at 405 AM EDT Sun AUG 21 2016

DISCUSSION...

The main low to midlevel cold front progressively pushed across the
cwa between 06-07z this morning. Not much of a fine line on radar
with the theta e discontinuity, but the front did allow for a small
wind pop behind the front of around 25 to 30 knots. Dewpoints have
lowered some 5 to 7 degrees during the past hour. Will likely see
dewpoints lower a few degrees during the course of the morning, then
hold for much of today.

The big differences in observations compared to earlier model runs
has been both a faster timing of the surface low and a difference in
positioning of the surface low pressure center. The surface low is
an approximate 200 miles farther north early this morning. Feel its
fair to say that its not solely because of the faster timing. What
this means for today is the gradient wind component will not be as
strong here over the DTX cwa, and thus some weaker than earlier
advertised surface winds are expected. As for the sensible weather
or precipitation forecast, not much of change is anticipated because
large wavelength to upper level trough. The main axis to the upper
level trough and resident shortwave energy will pivot into
southeastern Michigan this afternoon. Despite a lack of favorably
steep lapse rates, moisture and synoptic scale forcing will be good
enough to support a scattered to numerous coverage of showers during
the late afternoon. This is particularly true across the northern
and central sections of the cwa where models suggest most of the
strongest midlevel deformation now over NW Wisconsin and Western
U.P. will eventually eject across. There is enough convective
instability through a deep enough portion of the column to support a
chance of thunderstorms. No severe weather is anticipated. The
latest swody1 has all of the area in general thunder.

A very quiet period is expected for the early part of the week as a
high stability regime will be in place. Models are showing very
active subsidence Monday between 7 and 20 kft agl, with a very
stable column continuing on Tuesday. Conditions will be very
comfortable with highs Tuesday reaching the middle 70s and
temperatures eclipsing the 80 degree mark for all locations on
Tuesday.

MARINE...
Surface low north of Lake Huron will continue to pull away to the
northeast.  Tight surface gradient will produce a strong west wind
that will shift more to the northwest this afternoon, especially
across Lake Huron as a trailing surface trough moves through. Wind
gusts to about 35 knot gales across the north half of Lake Huron will
decrease by late morning with the approach of the surface trough.
This trough will also produce scattered showers and possibly a
thunderstorm with best coverage again being across Lake Huron.
Winds will quickly decrease tonight as surface high pressure
slides through.  Winds will become more southwesterly Monday from
return flow from departing high pressure and continue into Thursday
when the next system, a cold front, swings through the Great Lakes.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 8 PM EDT this evening FOR MIZ049.

Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon FOR LHZ421-422-
     441>443.

     Gale Warning until 4 PM EDT this afternoon FOR LHZ361-362.

Lake St Clair...Small Craft Advisory until 4 PM EDT this afternoon FOR LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 PM EDT this afternoon FOR LEZ444.

&&

$$

AVIATION.....SF
DISCUSSION...CB
MARINE.......DRC


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at www.weather.gov/detroit.



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