Expert Forecast Opinion

640
FXUS63 KDTX 170716
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
316 AM EDT Thu Sep 17 2026

.KEY MESSAGES...

- Light showers are possible this morning, primarily south of M-59.

- A short-lived dry period is expected Thursday night into Friday.

- Widespread showers return in earnest Saturday into Saturday night.
Rainfall totals in excess of half an inch are likely, with
the potential for 1 inch or more.

&&

.DISCUSSION...

Southeast Michigan will remain along the northern periphery of very
strong H5 600 dam ridge that will retrograde from the Southeast U.S.
to Texas by Friday. Quick progression of deep northern Canada
midlevel trough combined with the expanse of upper level confluence
over portions of the Great Lakes will support surface anticyclone
here locally and cause the frontal zone and any instability to be
suppressed to the south today. Despite the instability to the south,
plan view perspective of thermal progs show a fairly significant
wave of 850-600mb warm advection directly through Lower Michigan
between 06-18z this morning. Will see some upstream convection from
Iowa track eastward this morning and at least approach Southeast
Michigan. Could see some light precipitation or virga survive the
eastward trek but not expecting much in the way of rainfall amounts.
Persistent clouds today are expected to have some impact on
temperatures which will be in the middle 70s, at or a couple of
degrees above normal.

Retrogression of the high and deep column ridging will allow for
strong surface ridging over Southeast Michigan Friday. Cooler
morning lows with some 40s up north, but right at seasonal averages
for low temperatures.

Southeast US monsoonal moisture is forecasted to circumnavigate/
advect around the large Southeast US upper level ridge Friday and
Saturday. There has been good model consistency in supporting strong
synoptic scale lift from South Dakota Friday eastward into Michigan
on Saturday. Strong convergence streamflowing into a region of very
strong right entrance region jet dynamics aloft brings high
confidence in a storm track within the vicinity. Main concern is the
potential for heavy rainfall Saturday. EPS ensemble data highlights
an interquartile range of 24 hr QPF of .8 to 1.5 inches with higher
values in across the northern cwa including the Tri Cities. PoPs are
at 90-95% for the Day 3 period, the daytime on Saturday. The
Excessive Rainfall Outlook has much of Southeast Michigan designated
as a Slight Risk for Excessive Rainfall Saturday.

For the latter half of the weekend, indications are that an entrance
region to the upper level jet streak will stay in vicinity of
Southeast Michigan through at least Monday. Easterly flow combined
with differential cold advection in the low levels should result in
very stable weather with temperatures below normal. Confidence
decreases markedly with regards to precipitation potential by
Tuesday with hard to determine shortwave energy timing and location.

&&

.MARINE...

Winds remain on the lighter side (<20kts) through today as the
southern edge of northern Ontario high pressure slides overhead. A
secondary cold front drops through the region tonight-Friday with
the main impact being a modest uptick in northeasterly winds over
the southern half of Lake Huron. This front stalls over northern
Ohio before attempting to lift back north Saturday as Plains low
pressure arrives. This front looks to only push north of the
southern Great Lakes before the system tracks over lower MI
resulting in predominant east-southeast turning northeasterly winds
this weekend. Widespread showers and scattered thunderstorms are
possible, mainly focused over the southern half of the region. A
moderate gradient, supporting NE/E gusts 20-30kts, lingers behind
the low Sunday into the new work week as the area holds between the
stalled boundary over the Ohio Valley and high pressure over
northern Ontario.

&&

.PREV DISCUSSION...
Issued at 1146 PM EDT Wed Sep 16 2026

AVIATION...

Flattening ridge over SE CONUS forced most of the low stratus deck
to clear out this evening over SE Michigan. Low level moisture
however has started to return as a wave ripples along the existing
frontal zone, triggering isolated shower activity and bringing
ceilings back down to MVFR with a brief possibility for IFR around
daybreak. Shower activity is not all that impressive upstream, so
outgoing TAFs may be a bit aggressive with vsby reductions. Drier
air then filters in Thursday afternoon-evening to scatter out the
remaining cloud deck as a cold front drops across Lower Michigan.
Prevailing light northeast flow is anticipated through the TAF
period.

D21/DTW Convection...Thunderstorms not expected through the TAF
period.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less tonight through Thursday.


&&

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

$$

DISCUSSION...CB
MARINE.......KDK
AVIATION.....MV


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