937
FXUS63 KDTX 200252
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1052 PM EDT Sat Sep 19 2026

.KEY MESSAGES...

- Periods of rain return tonight though Sunday morning with locally
  heavier rainfall possible at times, and a few thunderstorms.

- Fog settles in overnight, becoming locally dense at times.

- Lingering showers exit by midday Sunday, followed by a cool and
  cloudy pattern into the middle of the week.

- Areas of showers are possible again late Tuesday into Wednesday.

&&

.AVIATION...

A weak surface low will continue to pivot along the stalled frontal
boundary that is in place at issuance, bringing renewed shower
activity to the area early Sunday morning. Ceilings have fallen
below 1.0 kft agl in most locations, with upstream observations
flirting with LIFR. Thus the expectation is for prevailing IFR with
occasional LIFR mixing in, particularly between about 08z and 13z
with additional moisture from showers. A rumble of thunder cannot be
entirely ruled out with the shower activity. Ceilings and visibility
improve Sunday as the front drops south, particularly in the
afternoon and evening, although it is still uncertain as to how
aggressively this trend will occur. VFR then becomes increasingly
likely in the afternoon and evening.

D21/DTW Convection...A rumble of thunder is possible as shower
activity works across the area late tonight into early Sunday
morning.

.DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 feet through Sunday morning.
  Medium Sunday afternoon.

* Very low for thunderstorms late tonight through Sunday morning.

* Low for cigs/vsby to fall below 200 ft and/or 1/2SM between 08z
  and 13z.

&&

.PREV DISCUSSION...
Issued at 352 PM EDT Sat Sep 19 2026

DISCUSSION...

Modest mid/upper level westerlies reside over the northern Great
Lakes and Ontario this afternoon while lower column flow orients
more southwesterly. This has led to steady moisture advection and
broad morning shower activity, most of which has briefly tapered
off. The main concern for this evening and overnight will be the
positioning of an elevated warm front which will anchor additional
shower activity, including the potential for a few thunderstorms.
Latest NWP tendencies indicate a southward shift in this axis,
favoring areas south of I-96/696 by late evening. CAPE metrics are
meager at best with lapse rates AOB 6.0 C/km. No severe weather
expected with any embedded thunderstorm structures. However,
boundary-layer condensation pressure deficits indicate a high
likelihood for areas of overnight fog. Potential exists for locally
dense patches at times, therefore, a Dense Fog Advisory may be
needed on short notice.

The large-scale pattern remains intact to start the day Sunday as
the geopotential height field stays perturbed. Expect additional
rounds of showers and perhaps a couple rumbles of thunder as the
warm sector aloft begins to retreat. Split flow moves in from west
to east overhead after 18Z, leading to subsidence/drying. Meanwhile,
1028 mb surface high pressure builds from Manitoba into central
Ontario, backing gradient flow northeasterly. This helps promote
further drying from north to south, dissolving lingering midday
shower activity confined to areas south of I-94. Some clouds may
linger into Sunday night, but temperatures should still hold around
5-10 degrees below climatological averages.

Unsettled conditions persist over the Ohio Valley early next week,
although the expectation is that the ridge should remain strong
enough and in proximity to Southeast Michigan to prevent much
spillover of showers into the Lower Peninsula. Thermal troughing
expands further across the Midwest, marked by 850 mb temperatures in
the mid single digits (Celsius), which suggests daily highs closer
to 10F below normal through Wednesday if not longer. A shortwave
feature aloft could close off somewhere over the northern Ohio
Valley late Tuesday into Wednesday. This would present the next
opportunity for additional rainfall, in slightly more widespread
fashion.

MARINE...

Stalled frontal boundary maintains shower chances over the southern
Great Lakes through Sunday. Expansion of strong high pressure over
northern Ontario finally shunts this front deeper into the Ohio
Valley. Locally, the central Great Lakes reside on the edge of this
high resulting in a respectable gradient across the region
throughout the entirety of the early week period. This supports
moderate northeasterly through Tuesday before shifting more easterly
by Wednesday (while maintaining strength). While gales currently
look unlikely, onshore flow warrants long duration Small Craft
Advisories for all nearshore waters.

HYDROLOGY...

Additional showers are expected overnight, some of which will be
capable of producing heavy rainfall, more so for areas south of M-59
where potential exists for training/repeated showers. Morning
rainfall was less productive than prior expectations, therefore
tonight`s flood threat is slightly lower. However, tonight`s shower
activity could lead to localized new rainfall totals in excess of 1
inch. Current data suggests the I-94 corridor to the Ohio border
will experience the highest chances for the highest rainfall rates.
Ponding in low-lying areas and urban flooding are the primary
threats, with minor rises on area rivers and streams likely.
Additional lighter showers may continue through Sunday morning,
before precipitation tapers off Sunday afternoon.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from noon Sunday to 10 PM EDT Wednesday for
     LHZ421-422-441>443.

Lake St Clair...Small Craft Advisory from 8 PM Sunday to 10 PM EDT Wednesday for
     LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 8 PM Sunday to 10 PM EDT Wednesday for
     LEZ444.

&&

$$

AVIATION.....MV
DISCUSSION...KGK
MARINE.......KDK
HYDROLOGY....KGK


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