595
FXUS63 KDTX 301947
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
347 PM EDT Wed Sep 30 2026

.KEY MESSAGES...

- Scattered to numerous light rain showers continue tonight and
  Thursday morning.

- Warm and humid Thursday as the coverage and intensity of showers
  increase.

- There is a chance for locally heavy rain Thursday night until
  ending with the passage of a cold front Friday morning.

- Low temperatures are projected to reach the mid to upper 30s north
  of metro Detroit by Saturday morning.

- Cool temperatures and dry weather continue through the weekend.

&&

.DISCUSSION...

The initial phase of our mid to late week rain episode is in
progress across Lower Mi this afternoon which continues in a similar
fashion tonight. Expectations for resident dry air in the low levels
as a limiting factor proved effective during the morning followed by
some gains in top down saturation this afternoon. Similar conditions
continue tonight as the initial mid level moisture transport and
small scale/low amplitude short wave forcing today shifts toward a
deeper and stronger low level jet driven configuration tonight. This
occurs under further surface frontal development spanning the Plains
states connected to the broad northern stream trough and 4 Corners
system. Low level jet forcing increasingly taps into the
tropical/Gulf hybrid moisture plume to fuel elevated instability and
scattered to numerous coverage of lower QPF showers tonight and
Thursday morning.

A transition toward the more intense phase of this event occurs
Thursday afternoon leading to a peak Thursday night, beginning with
the surface to mid level theta-e ridge building over Lower Mi in a
favorable position along and ahead of the Midwest cold front.
Forcing along and immediately post front is projected to increase
considerably due to a constructive combination of the inbound
northern stream mid level trough and entrance region of the upper
jet. The resulting increased QPF response in model solutions looks
good during this time as the stronger forcing combines with hybrid
tropical resulting in PW near 2 inches. QPF among the 30/12Z
deterministic models produce 6 hr totals around 1 inch in good
agreement with HREF and REFS PMMs over central/SE Mi Thursday night.
Flooding potential is mitigated slightly by the quick frontal
passage (see Hydrology Discussion below) that sweeps showers out of
the area Friday morning.

Surface high pressure spans the northern Plains and Midwest by
Friday morning which builds aggressively into the Great Lakes during
the day. It brings cooler and less humid air back into the region by
evening highlighted by guidance low temperatures projected to reach
the mid and upper 30s by Saturday morning. Rapid progression of
systems bring another low and cold front through the Great Lakes
Sunday. For now, this is a dry frontal passage for SE Mi followed by
reinforcing high pressure for early next week.

&&

.MARINE...

South to southwest winds will continue to slowly increase ahead of
the next cold front, which arrives and stalls over southern Lower
Michigan on Thursday. With warm advection leading to more stable
profiles and showers moving through during this timeframe, wind
gusts are expected to top out only around 25 knots. With the front
hung up into Thursday night, the post frontal cold advection now
looks slower; thus, the potential for northwest wind gusts reaching
or exceeding 25 knots looks to be late in the day on Friday as 850
MB temps lower into the mid single digits by Friday.

Another large area of high pressure building in on Friday night and
Saturday will promote light winds for the first half of the weekend.
A stronger low tracking through the northern Great Lakes for the
second half of the weekend brings another opportunity for winds to
reach or exceed 25 knots over Lake Huron.

&&

.HYDROLOGY...

A mid to late week rainfall episode continues to organize tonight
and Thursday, peaks Thursday night, and ends Friday morning. It
occurs as tropical moisture streams into Lower Michigan from the
southern Plains states, along and ahead of an approaching Midwest
cold front. The heaviest rain is forecast to occur between Thursday
afternoon and Friday morning with high confidence in rainfall totals
up to 1 inch and medium confidence in totals of 1 to 2 inches. A
more persistent band of rain is established across the area as the
cold front moves through the region Thursday night and when moisture
parameters peak with tropical remnants. QPF among the 30/12Z
deterministic models produce 6 hr totals around 1 inch in and around
the quick moving frontal zone across central/SE Mi. Within the model
probability space, there is a low chance for rainfall reach 2 inch
system totals if a slower frontal passage leads to more persistent
rainfall. All of the above points to a chance of minor flooding of
prone areas along with ponding water on roads across the region
until the rain quickly ends Friday morning.

&&

.PREV DISCUSSION...
Issued at 139 PM EDT Wed Sep 30 2026

AVIATION...

Gulf moisture continues to expand and hold across the Great Lakes
through the evening and overnight hours which will support extensive
cloud cover and rain showers. An elevated warm front will strengthen
which will increase coverage of rain across SE MI and will quickly
lower ceiling heights through the evening. Better moisture will
expand through KMBS down into KFNT tonight which will have the
higher probabilities to reach mvfr criteria for cigs and visibility.
A lull in precipitation coverage and improving ceiling trends are
likely through the Metro terminals and north through KPTK by the mid
to late morning hours tomorrow as flow backs to the southwest,
before a cold front brings the return of rain to all locations late
tomorrow. Cannot rule out an isolated thunderstorm but limited
instability will retain mostly rain chances for most locations
today.

D21/DTW Convection...Low potential for thunderstorms forecast this
evening and overnight.

DTW THRESHOLD PROBABILITIES...

* Low for ceilings at or below 5,000 feet through 20z. Medium 20z
  through the end of the TAF period.

* Low for thunderstorms this evening and overnight.


&&

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

$$

DISCUSSION...BT
MARINE.......SS
HYDROLOGY....BT
AVIATION.....AM


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