943
FXUS63 KDTX 150356
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1156 PM EDT Mon Sep 14 2026

.KEY MESSAGES...

- A chance of showers and thunderstorms returns Tuesday. The best
chance of storms and heavy rainfall is late afternoon and evening
south of I-69.

- A chance of showers lingers Wednesday before becoming more
numerous again Wednesday night and Thursday.

- Dry weather with temperatures around normal Friday into next
weekend.

&&

.AVIATION...

Thickening high based cloud overnight, as elevated moisture
transport increases along the southern flank of a strengthening low
level jet positioned north of the region. This process brings
potential for scattered shower activity late night and early
Tuesday, particularly from PTK northward, with overall coverage and
intensity likely limited too some degree by ample dry air held
within the lowest layers. This will support predominant VFR
conditions through this time. Prevailing wind from the southeast
tonight, veering to southerly with some modest gustiness for the
afternoon. Secondary window for convective development may emerge
along the cold frontal boundary Tuesday evening with a focus across
the Detroit corridor.

D21/DTW Convection...No thunderstorms are forecast through Tuesday
afternoon. A lower probability exists for thunderstorm development
Tuesday evening /21z-01z/.

.DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less Tuesday afternoon and evening.

* Low for thunderstorms Tuesday evening.

&&

.PREV DISCUSSION...
Issued at 327 PM EDT Mon Sep 14 2026

DISCUSSION...

High pressure has led to a dry but cool day across SE Michigan. Many
locations have seen temperature readings hold in the upper 60s, even
under plenty of sunshine. Anticyclonic surface wind pattern over
western Michigan identifies the center of the surface high, which
will drift overhead this evening and cause winds to back to the
southeast. Flow backs further to the southwest overnight, drawing a
theta-e ridge into the Great Lakes region Tuesday. This brings
warmer temperatures, increased rain chances, and breezy southwest
flow to SE Michigan.

The theta-e surge will be aided initially by a belt of ~50 to 60
knot h8 winds late tonight, driven on the larger scale by SE CONUS
high pressure. The nose of the jet reaches northern Michigan early
Tuesday morning, focusing a broad area of precipitation toward the
Saginaw Valley for the first half of the day. A deep closed low
across Ontario will simultaneously drag a cold front across northern
CONUS, which will push rain chances eastward and thus into the rest
of the CWA through the day Tuesday. One questionable aspect of this
system is how well the stratiform rain can hold up against the dry
airmass sampled overhead today (PWAT of 0.44" per 12z KDTX sounding
for reference). Soundings are showing a good amount of dry air
surviving at the low levels, which could eat into QPF amounts and
even rain chances altogether, especially as the low level jet
forcing departs mid-day Tuesday. The waning LLJ presence will still
be enough to produce breezy conditions with gusts of 25 to 30 mph
possible.

As the cold front and associated moisture convergence arrive Tuesday
afternoon-evening, event character becomes more convective with
showers and thunderstorms redeveloping along the boundary.
Instability is not expected to be overly impressive, but several
models bring 70 degree dewpoints across the state line Tuesday
evening which is enough for about 1000 J/kg MLCAPE. This occurs in a
fairly tight time window between about 21z-01z (5pm-9pm) south of I-
94. SWODY2 continues to designate a Marginal Risk for severe weather
across Lenawee/Monroe Counties, mainly for isolated precipitation
loaded downbursts in a marginal shear environment. The broader
threat looks to be heavy rainfall, especially given the high
moisture environment and proximity of the frontal zone. More details
are in the Hydrology section.

SE Michigan through the rest of the work week will be in the hands
of the frontal zone. The baroclinic zone certainly stays within
reach of us, but models generally shove it into the Ohio Valley for
Wednesday before lifting back north Thursday-Friday. Broad brushed
PoPs reflect the uncertainty in coverage/timing of this pattern
rather than a full wash out over the next several days. Wavering
nature of the frontal zone will also cause temperatures to waffle
between 70s and 80s through the rest of the work week with unsettled
conditions possibly extending into the weekend.

MARINE...

Strong high pressure over the Great Lakes tracks eastward this
evening, giving way to a mature low pressure system over the upper
Midwest. This system advances across northern Ontario on Tuesday and
directs a strong southerly low-level jet across the region. The
strongest winds are still on track for northern Lake Huron where
gales to 35 to 40 kt are forecast. A Gale Warning remains in effect
north of Alabaster from 4 AM to 4 PM. Farther south, gusts of 20 to
30 kt will be more common and Small Craft Advisories remain in
effect for the Lake Huron nearshore waters. A band of showers with a
few embedded thunderstorms accompanies the gale event with highest
coverage across Lake Huron during the morning. Additional scattered
showers and thunderstorms are forecast across Lake St. Clair and
western Lake Erie during the late afternoon and evening ahead of a
cold front. This front eases across the area Tuesday night, bringing
the end to showers and causing wind to shift from south/southwest to
north/northeast by Wednesday morning.

HYDROLOGY...

A moisture rich airmass surges into the region Tuesday ahead of a
cold front which tracks through in the afternoon and evening. The
front then stalls out across the northern Ohio Valley before lifting
back north later this week. This will result in multiple
opportunities for widespread rainfall throughout the week. In the
near-term, the best opportunity for heavy rain will be south of I-69
Tuesday afternoon and evening where thunderstorm development may
enhance rainfall rates to over an inch per hour. Depending on where
the front stalls, rain may linger overnight to produce storm totals
over one inch by Wednesday morning with training storms not out of
the question. Localized ponding or minor flooding of low-lying or
urban areas will be possible.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Warning from 4 AM to 4 PM EDT Tuesday for LHZ361>363.

     Small Craft Advisory until 4 PM EDT Tuesday for LHZ421-422-441.

     Small Craft Advisory until 4 PM EDT Tuesday for LHZ442-443.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....MR
DISCUSSION...MV
MARINE.......TF
HYDROLOGY....MV

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