797
FXUS63 KDTX 011922
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
322 PM EDT Mon Sep 1 2025

.KEY MESSAGES...

- Dry with seasonal temperatures into Wednesday.

- Showers Wednesday night will give way to much cooler temperatures
late week through the weekend. Additional shower chances late week.

&&

.DISCUSSION...

Clear skies and strong radiational cooling will give way to another
cool night with lows in the upper 40s and lower 50s, along with more
patchy, shallow ground fog.

Temperatures will moderate on Tuesday, then a bigger push of warm
air advection returns to the region ahead of a deepening upper-level
trough progged to track across the region later this week. This will
support a warming trend through mid week, with daytime highs
climbing into the uppers 70s and lower 80s on Tuesday. Overnight
lows will exhibit a slight warming trend as well, but we should
still maintain the comfortable overnight temperatures with lows
falling into the 50s. A few models are hinting at a weak area of
focused low-level convergence developing coincident with peak
heating Tuesday afternoon across northern and central lower
Michigan. The boundary layer will certainly be well mixed, with high-
based cumulus developing Tuesday afternoon. However, ensemble
guidance show very limited (if any) convective development this far
south on Tuesday afternoon, due to a lack of large-scale ascent and
overall dry boundary layer conditions. Thus have kept the forecast
for Tuesday dry.

By Wednesday, lagre-scale gradient flow increases with breezy
southwest winds ushering in a warmer airmass supporting daytime
highs climbing into the low to mid 80s. The warmest conditions are
expected along and south of the Irish Hills, and will be short-
lived. As the above mentioned upper-level trough digs into the
region, it will push a strong cold front south across the state late
Wednesday into Thursday morning. Current guidance has the cold front
sneaking into central Michigan sometime late afternoon/early evening
on Wednesday, then pivoting across the area into early Thursday
morning. The likelihood of seeing precipitation across all of
southeast Michigan has increased compared to the previous forecast
update, with around 0.50 to 0.75 inches of rain expected over a 3-6
hour window. While there will be not much in the way of instability
to work with, strong large-scale ascent will accompany the cold
front and associated convection. Thus did maintain thunderstorm
mentions in the forecast.

Behind the departing cold front, a cooler Canadian airmass
overspreads the region and brings significantly cooler temperatures
for the end of the week and into next weekend. Daytime highs will
fall 10 to 15 degrees below normal for this time of year, with highs
only climbing into the 60s. Overnight lows are forecast to fall into
the 40s, but we will see some dependency on how cool temperatures
get based on cloud cover trends. The pocket of colder air moving
through the region will remain in place through next weekend as the
main upper-level low slowly moves east across Ontario. Occasionally
rain showers are possible, especially on Friday as another shortwave
embedded within the mean flow tracks east across the region.

&&

.MARINE...

Sprawling high pressure now centered over the Eastern Great Lakes
providing light and variable winds, which looks to continue into
Tuesday with dry conditions. There is a low chance for some fog to
develop late tonight due to the warm waters and very light winds.

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.

&&

.PREV DISCUSSION...
Issued at 1257 PM EDT Mon Sep 1 2025

AVIATION...

Resident high pressure supplies another day of ideal aviation
conditions while holding in place from the upper Midwest across the
Great Lakes. A near repeat performance of Sunday is in progress as
VFR consists of shallow cumulus expanding to generous scattered or
briefly broken coverage with light east wind. These clouds dissipate
with sunset this evening followed by another round of clear sky over
Lower Mi late tonight into Tuesday morning. High pressure is in a
better position to maintain light easterly wind across Lake Huron
and Erie for a weak marine influence on surface/boundary layer
moisture. Wind speed has lower predictability due to a weak pressure
gradient at night, so the forecast will carry a few hours of MVFR
fog restriction while monitoring trends for lower thresholds into
Tuesday morning.

For DTW/D21 Convection...No thunderstorms today through Tuesday.

THRESHOLD PROBABILITIES...

* None


&&

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

$$

DISCUSSION...JA
MARINE.......SF
AVIATION.....BT


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