036
FXUS63 KDTX 160700
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
300 AM EDT Wed Sep 16 2026

.KEY MESSAGES...

- Rain and thunderstorm chances continue into the midweek period.

- The weekend indicates showery weather but mild temperatures
Saturday and Sunday.

&&

.DISCUSSION...

Very strong H5 599 dam mid-upper level high pressure over Southeast
US will slowly retrograde to portions of east Texas and OK by
Friday. The upper level jet axis over eastern Canada will be slow to
move which will keep the baroclinic zone in relatively close
proximity to Southeast Michigan through at least the end of the week
and beginning of the upcoming weekend.

For today, plan view perspective of thetae shows the near surface
extension of the frontal zone slipping southward to the Ohio border
while the 900-700mb frontal surface remains farther north between
the I 96-I 69 corridors. Differences exist with regards to the north
south extent of shower/convective development later today. Consensus
of many of the models including NAMnest and HRDPS initiates deep
convection to the south of IN/OH state line, whereas the ECMWF
brings QPF (from weaker elevated showers) much father north through
much of Southeast Michigan. System relative flow trajectories
highlight a coherent 925-850mb cyclonic circulation emerging today
near South Bend that will track eastward increasing convergence.
Models suggest shower activity approaching after 14z with spotty
activity in an around the area this afternoon. Out of respect for
the elevated portion of the frontal zone and the progged
convergence, will keep inherited broad brushed PoPs.

Despite little north to south movement of the upper level jet axis,
the entrance region and confluence aloft will support stable surface
high pressure late Thursday and Friday. Strong likelihood that
increasing anticyclonic flow trajectories will result in lower
dewpoints into the 50s. A comfortable couple of days.

Right entrance region to very large jet entrance brings the
potential for upstream convection to ride eastward through Lower
Michigan. There has been a subset of solutions that have a MCS
developing over the Plains states Friday and arriving over Southeast
Michigan midday Saturday. Breadth of synoptic scale forcing with
time of year suggests heavy rainfall potential. The latest Excessive
Rainfall Outlook products have been highlighting a Slight risk for a
good portion of Southeast Michigan. Given the structure an
organization of the thetae ridge a wave will act upon, the setup
looks good. The current forecast as 80-90% PoPs for Saturday.
Another trough structure does look to suppress heights and cause a
cold front to slip southward for Sunday.

&&

.MARINE...

A weak cold front gradually settles across the southern Great Lakes
this morning, shifting wind direction to north and northeast in its
wake with brief gustiness to around 15-20 kt over Lake Huron. High
pressure passes across the northern Great Lakes today, favoring
lighter winds and dry weather through the afternoon. The cold front
stalls near the southern Great Lakes this evening, sustaining a
chance for showers and storms mainly near Lake Erie into tonight and
Thursday. The gradient strengthens Thursday evening as another area
of high pressure builds into northern Ontario, producing an uptick
in northerly winds early Friday morning. Given the long fetch into
southern Lake Huron, will monitor the need for a Small Craft
Advisory for high waves reaching the nearshore waters Friday morning.

&&

.PREV DISCUSSION...
Issued at 1225 AM EDT Wed Sep 16 2026

AVIATION...

Thunderstorm clusters exiting the DTW corridor at forecast issuance
are followed by the cold front that also exits south and east before
sunrise. The forecast focus then turns to cloud conditions along
with any stray showers or rumble of thunder post front through the
morning. Expansion of MVFR stratus with a fog component are
maintained in light and variable wind that turns NE off Lake Huron
in the low levels, and as breaks in mid/high clouds allow some
boundary layer radiational cooling. Borderline MVFR/low VFR ceiling
then continues through the afternoon, especially toward DTW with the
cold front still nearby to the south. This is also where the
potential for showers and a rumble of thunder are greatest, although
timing predictability is on the low side. Farther north, the inbound
high pressure air mass has just enough dry air to combine with
daytime heating and nudge the cloud edge south of MBS mid to late
afternoon.

D21/DTW Convection... A rumble of thunder lingers during the late
night as the cold front moves through the region before sunrise.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less late tonight and Wednesday.

* Moderate for thunderstorms before sunrise.


&&

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

$$

DISCUSSION...CB
MARINE.......TF
AVIATION.....BT


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