442
FXUS63 KDTX 151953
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
353 PM EDT Tue Sep 15 2026

.KEY MESSAGES...

- Redevelopment of rain showers and some isolated thunderstorms will
be possible tonight and overnight, along or south of M59.

- There is a low chance for strong to severe thunderstorm
development with this activity.

- Rain and thunderstorm chances continue into the midweek period.

&&

.DISCUSSION...

Expansion of high pressure across the upper Midwest will progress a
cold front into southern Michigan where the boundary is then
expected to slow and stall out tonight. This will retain an area of
enhanced theta-e across southern Michigan overnight, characterized
by PW values nearing 2" closer to the MI/OH border along with 850mb
dew points ranging between 12-14C. Low level convergence and weak
shortwave impulses within this region of higher moisture will be the
focal point for renewed showers and possibly thunderstorms this
evening through at least tomorrow morning.

For tonight, expansion of renewed showers and isolated thunderstorms
will be more favorable around and south of M59. Any arrival of
convection between 23Z - 02Z may be able to capitalize on a brief
increase in surface instability along the nose of enhanced theta-e
ahead of the cold front. This coupled with moderate low to mid level
lapse rates and 0-6km bulk shear around 35 knots will bring some low
end chances for an isolated strong to severe thunderstorm. Any
stronger development will be capable of producing localized stronger
wind gusts from a wet microburst. SR-hodographs also show a modest
streamwise component from 0-3 km, highlighting potential for some
better organization, but all said, poor buoyancy with unfavorable
timing of convective potential will be a major hindrance to any
robust convection. SWODY1 highlights a marginal risk for several
weather for this activity.

Severe chances are then mitigated overnight once surface instability
wanes and conditions turn more elevated. Zonal low to mid-level flow
will bring continuation of shower and storm potential overnight
through tomorrow afternoon. Any repeated shower and thunderstorm
will have the low potential to bring localized flooding in flood
prone locations. See the hydrology section for additional details.

The frontal boundary will waver across southern Michigan late
Wednesday into Thursday, providing additional chances for showers
and thunderstorms through the midweek period. Some respite from rain
chances will be likely late Thursday into Friday as the southern
periphery of high pressure builds in across the Great Lakes, but
additional chances for showers and storms, possibly heavy rain, will
re-enter on Saturday as storm complex derives from the Plains
progresses into a stronger baroclinic zone. There is uncertainty
this far out regarding where any enhanced forcing will align, with
mid-range models highlighting anywhere from central Michigan to
locations south into the Ohio Valley as potential zones for elevated
QPF.

&&

.MARINE...

An occluded low pressure system tracks into Hudson Bay this evening
with its southwesterly low-level jet easing out of the northern
Great Lakes with time. The core of the strongest winds has already
exited the area and the Gale Warning will be allowed to expire on
time at 4 PM. The system pushes a cold front across the area
overnight, causing southwesterly wind to quickly veer to north and
northeast by Wednesday morning. Ahead of the front this evening and
overnight, additional scattered showers and a few thunderstorms will
be possible mainly for Lake St. Clair and western Lake Erie. An
isolated storm may be strong to severe with wind in excess of 34 kt
the main threat. High pressure passes to the north of the lakes on
Wednesday, sustaining continued northeasterly flow of 10 to 15 kt. A
chance of showers and storms lingers around the southern Great Lakes
through Wednesday and Thursday as the cold front stalls in the
vicinity.

&&

.HYDROLOGY...

Redevelopment and expansion of rain showers with some embedded
thunderstorms will be possible tonight and overnight, most favorable
along or south of M59. Any thunderstorm development will be capable
of producing brief but heavy downpours. New rainfall totals from
this afternoon through tomorrow morning are expected to range between
a quarter-inch to a half-inch, however, any thunderstorm development
will likely produce highly localized totals that reach or exceed one
inch. This will bring a low chance for localized road flooding or
minor flooding of low-lying and urban area through tomorrow.

&&

.PREV DISCUSSION...
Issued at 1242 PM EDT Tue Sep 15 2026

AVIATION...

Regional radar suggest areas of showers and isolated thunderstorms
likely to continue during the early to mid afternoon hours as mid
level short wave energy track along an elevated frontal boundary and
moisture axis. Observational data indicate the greatest coverage of
showers will remain at PTK northward during the afternoon. The
advection of instability into metro Detroit during the late
afternoon and evening will increase the chances for thunderstorms
tonight, with the probabilities highest in the 03Z to 06Z time
frame. The development of low level inversion tonight and ample low
level moisture in place will increase the chances for MVFR
conditions in both ceilings and visibility restrictions late tonight
through Wednesday morning.

D21/DTW Convection...Increasing elevated instability is supporting
additional convection across SW Lower Mi early this afternoon, which
may impact portions of the metro airspace this afternoon. Additional
convective development is forecast later this evening along the lead
edge of an axis of instability lifting into the area from the
southwest.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less this afternoon and evening. High
  tonight and Wednesday.

* Moderate in thunderstorms today and tonight.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Warning until 4 PM EDT this afternoon for LHZ361>363.

     Small Craft Advisory until 4 PM EDT this afternoon for LHZ421-422-
     441>443.

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

$$

DISCUSSION...AM
MARINE.......TF
HYDROLOGY....AM
AVIATION.....SC


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