951
FXUS63 KDTX 020953
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
553 AM EDT Tue Sep 2 2025

.KEY MESSAGES...

- Warm and breezy Wednesday.

- Showers late Wednesday afternoon through Wednesday night will user
  in much cooler temperatures for late week into the weekend.

&&

.AVIATION...

Extended period of high pressure influence persists for one more
day, ahead of an Upper Midwest low pressure system encroaching on
the state by Wednesday. Today`s conditions reflect those of the last
several days, characterized by diurnal SCT-BKN VFR boundary-layer
cumulus near 7 kft AGL and light wind speeds (below 10 knots). Main
difference wrt surface winds arises during the afternoon hours as
collective veering brings about a southerly wind shift. This is
largely in response to the downstream propagation of the
aforementioned low and its attendant cold front. Some cloud fraction
expected overnight, mainly aloft as cirrus moves in from the
northwest.

For DTW/D21 Convection...No thunderstorms expected today or tonight.

THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 306 AM EDT Tue Sep 2 2025

DISCUSSION...

Slight mid level ridging and associated negative vorticity
advection is forecast to slide across Se Mi this afternoon from the
northeast. Model soundings indicate this will reinforce the mid
level capping inversion, maintaining dry conditions with just
scattered high based diurnal clouds. Subtle low level warm air
advection within a light south-southeast flow today will support
afternoon highs around 80. Ideal radiational cooling will exist
through the first half of tonight before the southwesterly gradient
flow increases, leading to a little warmer nighttime mins in
comparison to the last few nights; mid 50s to around 60.

Southwest flow will strengthen on Wednesday in response to a
deepening upper low dropping into nrn Minnesota and wrn Lake
Superior from northern Canada. Corresponding low level warm air
advection and deep daytime mixing depths will result in a warm and
breezy day Wednesday, with highs hitting the low 80s across much of
the area. The lead edge of the mid level height fall region
accompanying the deepening upper low will move across Lower Mi Wed
afternoon into Wed night. A plume of deep layer moisture in advance
of the mid level positive vorticity axis and along the associated
cold front will interact with the large scale ascent to produce
widespread showers across the area. The majority of ensemble
guidance bring the showers into the Tri Cities region Wed afternoon,
with the ascent and associated axis of showers slowly crossing the
rest of the forecast area Wed night. The NAM solution is even
suggesting the mid level trough axis take on a slight negative tilt
as it rolls across Se Mi Wed night. This and highly difluent flow
aloft suggests an intensification of deep layer frontogenesis along
the mid level front as it crosses the forecast area Wed night.
Despite weak instability, the potential strength of the forcing will
remain supportive of a chance of thunderstorms.

The airmass which will be driven into Se Mi in the wake of the cold
front on Thursday will be fairly cold for early September with 850mb
temps dropping into the low single digits across Se Mi, resulting in
highs from the 60s. While the upper low is forecast to continue to
deepen as it rotates across nrn Ontario Thurs, a region of mid level
dry air is forecast to reside across srn Mi through the day
Thursday. While the cold air aloft will likely support a decent
strato cu field, precip chances will remain limited. There has been
growing model consensus in indicating a secondary mid level wave
pivoting around the deep upper low over nrn Ontario across tracking
across Lower Mi on Friday, proving a good chance for additional
showers. This wave will also deliver a reinforcing shot of cold air
for the start of the weekend.

MARINE...

Sprawling high pressure over the Eastern Great Lakes will provide
one more day of light winds today. Weather will deteriorate
Wednesday as a low pressure system and cold front drops south into
the Central Great Lakes, leading to developing showers and possible
embedded thunderstorms. This front will drive much colder air across
the lakes for Thursday, ushered in by strong northwest winds (20-30
knots). Another low pressure system diving southeast from Central
Canada will deliver a second shot of cold air, which will support a
chance of waterspouts and isolated showers for the Weekend. Out
ahead of the low on Friday, southwest winds have the potential to
reach gales over Lake Huron, but confidence is still low as near
lake stability looks to to be neutral, and will hold wind gusts
around 30 knots/maybe brief gales. With the cold advection on
Saturday, westerly wind gusts look to be around 30 knots and flirt
with low end gales as well, particularly over the northern third of
Lake Huron.

HYDROLOGY...

A strong cold front will bring showers and a few thunderstorms to
the forecast area from Wednesday afternoon through early Thursday
night. The more meaningful measurable rain will likely occur over a
6 hour or less time period. Ensemble members indicate the higher
probability rain totals will fall between .2 and .6 inches. There
are however some members which have total rainfall of .8 inch to 1.2
inches, enough to suggest a low chance for rain totals to approach
an inch.

&&

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

$$

AVIATION.....KGK
DISCUSSION...SC
MARINE.......SF
HYDROLOGY....SC


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