278
FXUS63 KDTX 122303
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
703 PM EDT Sat Sep 12 2026

.KEY MESSAGES...

- Potential for a few showers to develop Sunday afternoon primarily
north of I-69.

- Cool Sunday Night: Low temperatures fall into the 40s Sunday night
as high pressure and cooler air settles over the area.

- Unsettled Midweek: Warmer and humid conditions return early next
week, bringing multiple waves of showers and thunderstorms Tuesday
through Thursday.

&&

.AVIATION...

Standard decline in lingering diurnal VFR cu with loss of daytime
heating early this evening, as an increase in mid level moisture
brings a noted uptick in higher based cloud coverage for the
remainder of the evening. This occurs ahead of a cold frontal
boundary set to sag into the region during the early-mid morning
hours. Improving low level moisture along the frontal zone will
support a period of MVFR cloud development late tonight -
particularly from PTK northward. Post-frontal wind shift to north-
northeast for the morning period. Drying boundary layer conditions
will effectively lift and scatter this cloud field through the day.
Conditions may become favorable for a lower coverage of showers,
with a rumble of thunder Sunday afternoon.

D21/DTW Convection...No thunderstorms are expected through Sunday
morning. Very low potential Sunday afternoon.

.DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling 5000 ft or less after midnight tonight
  through Sunday morning.

* Very low for an isolated thunderstorm Sunday afternoon.

&&

.PREV DISCUSSION...
Issued at 300 PM EDT Sat Sep 12 2026

DISCUSSION...

850-700mb moisture gradient collocated with general midlevel
stretching deformation served as a focus for midlevel altocumulus
congestus development during the late morning hours along a line
from Manchester to Harbor Beach. A secondary diffuse surface based
warm front is also lifting northward out of Ohio into portions of
Southeast Michigan for the early afternoon. Residual convective
inhibition off of the high pressure from recent days is forecasted
to hold in some fashion between 4.0-10.0 kft agl. So there will be
some background deterrent for upward motion due to the capping
inversion. Poor model signal exists but 75-90th percentile of NBM 12
hour QPF progs does suggest some sporadic, isolated shower activity
this afternoon. Do think that the low potential for a thunderstorm
will come after 20z south of the I 69 corridor along the surface
based front. Daytime heating with the richer boundary layer moisture
suggests MLCAPE of around 1000 J/kg will be possible with 0-6km bulk
shear of 25 knots or less. No severe weather is anticipated.

Surface cold front and dewpoint gradient will begin a journey
southward tonight that will slow down in vicinity of Southeast
Michigan. Models suggests a backdoor cold front working southward
overnight before stalling in the Thumb. Complex setup for early
Sunday with midlevel ridging component overhead as surface ridging
tries to expand eastward. Composite trough axis with shortwave then
digs into Southeast Michigan but really appears to be out of phase
with any of the favorable dynamics of the upper level jet streak.
Low chance of showers and/or rumble of thunder appears inevitable
Sunday afternoon but will likely require true absolute vorticity
advection. As a result, precipitation chances Sunday look to hold
off until after 20z with some very modest midlevel fgen.

Much less humid air will be ushered into Southeast Michigan with
cooler temperatures for Monday. Strong surface high pressure is
progged so any instability type shower potential should be highly
limited to any lake effect activity. Clear skies with highs around
70 degrees.

Surface high pressure will remain very progressive tracking out of
Lower Michigan by Tuesday. Models show significant warm air and
dewpoint advection for Tuesday with highs climbing back above 80.
Details need to be ironed out yet but greatest dynamic support for
ascent appears likely for northern Wisconsin and the U.P. associated
with strong upper level jet forcing. Dipole subsidence under strong
extension to upper level ridge may hold for a time Tuesday before a
far reaching baroclinic/frontal zone sags southward into the
northern forecast area. A wet period then appears in store with
convection possible/persisting along the edge of the instability
reservoir. There is a model signal that suggests a wave of
frontogenesis and low pressure will work through the northern Great
Lakes region late Wednesday and Wednesday night. Will need to
monitor for possible thunderstorm/MCS potential.

MARINE...

High pressure over eastern portions of the Great Lakes region will
continue to push eastward this afternoon.  At the same time, low
pressure over northern Ontario has been pulling a cold front over
northern portions of the Great Lakes bringing scattered showers and
thunderstorms. The front will move off to the east overnight as a
short period of dry weather before isolated shower chances come back
in by Sunday afternoon. Moderate trailing northwest flow develops
over northern Lake Huron during the daytime on Sunday with peak
gusts between 25 to 30 knots. A more dynamic system then lifts out
of the Plains and over the northern Great Lakes Monday night into
Tuesday. Preceding warm, humid airmass will fuel better scattered
storm chances during this time.

&&

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

$$

AVIATION.....MR
DISCUSSION...CB
MARINE.......SS

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