Expert Forecast Opinion

023
FXUS63 KDTX 222325
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
725 PM EDT Tue Sep 22 2026

.KEY MESSAGES...

- Extended stretch of seasonably cool conditions will exist thru the
mid-week period.

- Aside from a low chance of rain tonight and Wednesday mainly south
of I-94, dry conditions are expected through next weekend.

&&

.AVIATION...

A weakness and greater relative midlevel cyclonic flow amidst rex
blocking will edge northward into portions of the Lake Erie basin
tonight. Models show deeper moisture and greater deformation
potentially activating lake effect rain showers that will push into
the forecast area from the east. Confidence is still lacking that
rain shower activity will impact DTW and YIP. MVFR is anticipated.
Daytime heating is expected to result in top of the boundary layer
saturation and cloud. Low VFR to possible MVFR.

D21/DTW Convection...Thunderstorms are not forecast through the
forecast period.

.DTW THRESHOLD PROBABILITIES...

* Moderate in ceilings aob 5000 feet today and tonight.

&&

.PREV DISCUSSION...
Issued at 339 PM EDT Tue Sep 22 2026

DISCUSSION...

Transition day in the upper levels as we go from split flow pattern
into an amplified blocking pattern with Plains ridge in between
coastal troughs. In getting there, we`ll be presented with the only
chance for precipitation for about the next week, and even that
chance is only for the far southern locations mainly south of I94
tonight into Wednesday. Cause of this rain chance will be an upper
low now over northern IL which will drift eastward in the weak flow
on the south side of the split flow pattern while phasing with an
elongated trough dropping out of the northern split and also reside
weak troughing currently over the east coast. Models have been
consistently showing a narrow axis of low level convergence around
Lake Erie reaching into southern MI concurrent with mid level
deformation north of the low and with a plume of enhanced theta e
retrograding west around the north side of the low. Saturated layer
in model sounding still up to around 10kft tonight but now extends
further to around 15kft during the day Wednesday. Moisture does
become more elevated with developing dry layer in the low level so
chances of rain extending into Wednesday afternoon are low. High
chance pop low QPF event for southern MI Tuesday night with less
than a tenth of liquid for those that see any rain.

Heading into the weekend, the next longwave trough will come ashore
the Pacific NW causing the Plains ridge to amplify setting up the
blocking pattern across the conus. The expansive surface ridge to
the north keeps easterly flow through the weekend allowing for only
slowly moderating temperatures with the thermal trough holding over
the region. So highs in the 60s will carry through the weekend
before the ridge axis reaches lower MI allowing for southerly flow
to return boosting temps back into the low 70s. With good amount of
clear skies at night, favorable radiational cooling setup will allow
lows to drop into the 40s each night.

MARINE...

Modest east-northeasterly gradient winds persists over the central
Great Lakes through Wednesday as an expansive 30.50 inHg high
pressure system builds further east into Quebec. This sustains
elevated on-shore waves for most of the waterways, therefore, a
Small Craft Advisory remains in effect for all nearshore waters
until Wednesday night. The diurnal boost to gusts has been muted
compared to prior thinking as peak afternoon speeds remain below 30
knots. Still monitoring a Rex Block that should emerge overhead by
Wednesday with the closed low positioning over the northern portion
of the Ohio Valley. This alters the pressure and moisture fields,
intersecting a stalled/deteriorated elevated frontal boundary. This
may lead to some light showers over the far southern waterways (i.e.
western Erie) by Wednesday morning. Wind speeds gradually start to
decline through the latter half of the week as the pattern unlocks,
and split flow returns aloft after the surface pressure gradient
relaxes. Wave heights should recover accordingly, precluding the
need for any extensions to the ongoing Small Craft Advisories.

&&

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

Lake St Clair...Small Craft Advisory until 10 PM EDT Wednesday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT Wednesday for LEZ444.

&&

$$

AVIATION.....CB
DISCUSSION...DRK
MARINE.......KGK


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