Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 211844

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


Scattered to numerous showers with a few thunderstorms will persist
late this afternoon into early this evening as a notable vorticity
lobe pivots around mean upper low pressure of Hudson Bay and drives
a secondary surface trough/cold front through lower Michigan. Timing
of this features as it exits the forecast area will coincide with
the loss of daytime heating/peak instability, so this activity will
fade very quickly in the 23z-01z time frame with minimal coverage
for the rest of the evening. Breezy conditions with winds gusting to
20 or more mph will also diminish quickly as boundary layer mixing
eases this evening.

Overnight, the only remaining showers will be lake effect activity
brushing the Thumb shore as cool northwest flow produces modestly
unstable conditions over the relatively warm lake waters. Otherwise,
skies will become clear/partly cloudy over the remainder of the
forecast area as surface high pressure begins to build into the
central Great Lakes. Temperatures will respond to the relatively
clear/calm conditions and drop well into the 50s over much of the

Quiet conditions will ensue early in the week as this high builds
across the area. Relatively cool conditions (as compared to this
summer`s warmth) will persist on Monday as highs climb into the mid
to upper 70s which is rather close to average high temperatures this
time of year. Humidity levels will also be notably low in this dry
airmass from the north/northwest.

Upper heights are already building on Monday/Monday night as upper
trough pivots to the east/northeast. By tuesday, shortwave ridging
then progresses into area in response to building upper trough over
the northwest/north central CONUS. This will allow temperatures to
climb back into the 80 to 85 degree range. With upper ridge over the
area, no precipitation is expected through the Tuesday/Tuesday night
time frame.

Upper ridging will give way to lowering heights Wednesday as a lead
wave and accompanying moisture surge may allow for precipitation to
develop as early as Wednesday. Best chances for precip in the
extended during the Wednesday night/Thursday period ahead of frontal
boundary. Dry forecast favored behind the front Friday and Saturday.
Temperatures Wed/Thur slightly above normal, easing toward normal



Surface ridge axis building into the Central Great Lakes Tonight
will allow winds to become light, under 15 knots. Based on current
observations and relaxing pressure gradient, have allowed Gale
Warning for Northern Lake Huron to expire on time.

Return southwest flow around departing high pressure will increase
to around 20 knots over Central Lake Huron on Tuesday, including
Saginaw Bay. Winds will decrease just a bit on Wednesday as cold
front tracks into the region, likely producing showers
and thunderstorms by Wednesday Night.


Issued at 104 PM EDT Sun AUG 21 2016


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.


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-

     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.




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