407
FXUS63 KDTX 300742
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
342 AM EDT Sat Aug 30 2025

.KEY MESSAGES...

- Seasonably cool today, although a gradual warming trend gets
  underway until mid-week.

- Dry conditions expected through Tuesday, then rain and thunderstorm
  chances arrive Wednesday.

&&

.DISCUSSION...

Gradual geopotential height rises are underway early this morning as
a seasonally strong PV anomaly slowly exits into The Northeast. This
gives way to a broadening region of 1023 mb surface high pressure,
which eventually encompasses most of the western and central Great
Lakes. After a calm morning start, winds remain similarly weak
through the daylight hours given the unimpressive surface pressure
gradient. Only other noticeable change in sensible conditions will
be the moderating temperatures as 850 mb temperatures warm by
approximately 3C. No precipitation concerns amidst increasing mid-
level subsidence and column drying, as evidenced by PWATs dropping
below 0.75 inches. Similar conditions expected Sunday and Labor Day
as thermodynamic profiles moderate further, to near climatological
normals. Meanwhile, an upper level ridge spills southeast from the
northern Canadian Prairies into Ontario while an embedded shortwave
trough transits the back edge of the departing upper low, dislodging
and closing-off over Appalachia Sunday night. This quasi-Rex Block
over the broader region keeps the warmest 850 mb temperatures over
northern Ontario and Hudson Bay (upper teens Celsius) until the
northern stream jet quickly shears the ridge out during Labor Day.
Expect a steady uptick in daily highs, eventually into the upper 70s
early next week while rain-free conditions persist.

The synoptic pattern becomes disentangled Monday night into Tuesday
as a northern stream 550 dam 500 mb low drops into the Upper
Midwest, phasing with a portion of the southern branch. At the
surface, resilient high pressure takes until Tuesday night or
Wednesday to break down allowing gradient flow to organize out of
the south. A wave takes shape over the Lower Mississippi Valley
before it lifts into the Ohio Valley, ushering in an increasingly
humid airmass. The combination of converging dynamics aloft, an
impinging cold front from the northwest, and growing potential for
destabilization culminates in the first precipitation chances of the
forecast period on Wednesday. Most medium-range solutions produce a
swath of rainfall followed by perhaps the coldest airmass of the
summer. Operational ECMWF has aligned with the GFS by bringing the
0C 850 mb isotherm to Lower Michigan within the next cold-core low.
Ensemble systems suggest potential exists for late-week high
temperatures below 60F across parts of Southeast Michigan.

&&

.MARINE...

A high pressure system will hold across the Great Lakes this weekend
into early next week. This will sustain dry weather and more
tranquil conditions. The next chance for more active weather will
enter during the mid to late week time frame as a low pressure/cold
front nears the Great Lakes.

&&

.PREV DISCUSSION...
Issued at 1149 PM EDT Fri Aug 29 2025

AVIATION...

Surface high pressure overhead will result in light and variable wind
tonight. Prior moisture fluxing off of the Great Lakes may keep a
few patches of VFR cloud around the region overnight. No real signal
in the model soundings for any fog at daybreak, but a small
potential exists particularly at those taf sites outside of the urban
heat island. Surface high pressure and dry airmass will perpetuate
VFR conditions Saturday.

For DTW/D21 Convection...No thunderstorms during the period.

THRESHOLD PROBABILITIES...

* None


&&

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

$$

DISCUSSION...KGK
MARINE.......AM
AVIATION.....CB


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.