National Weather Service United States Department of Commerce


041
FXUS63 KDTX 280946
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
546 AM EDT Mon Jul 28 2025

.KEY MESSAGES...

- A heat advisory is in effect today for heat indices near 100
degrees.

- There is a chance of thunderstorms today and Tuesday.

- Dry weather highlighted by cooler temperatures and much lower
humidity arrives for the late week period into next weekend.

&&

.AVIATION...

Patchy fog early this morning dissipates around the start of the new
forecast period giving way to VFR conditions for the remainder of
the morning. Cirrus debris from ongoing storms dropping through IL
streams into the region this morning before diurnal cu develops in
the afternoon. High pressure weakens today offering chances for
widely scattered convection late afternoon-evening. Overall chances
aren`t particularly high, and likely depend on strength of lake
breezes for a trigger mechanism, though still enough to warrant a
Prob30 mention across the terminal corridor.

For DTW/D21 Convection... Isolated to widely scattered thunderstorm
development is possible late afternoon into the evening - especially
along lake breeze boundaries.

THRESHOLD PROBABILITIES...

* Low for thunderstorms this afternoon.

&&

.PREV DISCUSSION...
Issued at 304 AM EDT Mon Jul 28 2025

DISCUSSION...

Mid level anticyclonic flow now over the eastern Great Lakes has
held a dry forecast across Se Mi during the night and will continue
to do so through the morning. The MCS now ongoing over srn Minnesota
will track southeast along the instability gradient and into IL/MO
this morning. A forecast weakening trend is likely to limit the
extent of high cloud debris into Se Mi, offering ample diurnal
heating into the afternoon. Light SSW flow in the boundary layer
will sustain sfc dewpoints around 70 to the low 70s (possibly mid
70s in the south) with subtle low level warm air advection
supporting afternoon highs in the low to possibly mid 90s,
predicated on any convection occurring past peak heating. This will
push afternoon heat indices toward 100 degrees over most of the area
today, warranting a heat advisory for the entire forecast area.

Recent CAMs solutions do suggest potential for late day convection
across the forecast area. While some solutions suggest only isolated
convection, others actually develop several clusters of convection
by late afternoon. While the main MCV associated with the srn MN
complex should track south of the state, some semblance of mid level
troughing combined with weak sfc boundaries may be enough to
initiate convection. Model soundings indicate that diurnal heating
has the potential to push 0-1km MU Cape values to 2000 to 2500 J/kg.
While there will be ample low level moisture, the deep tropical
moisture looks to remain south of the state with lingering dry mid
level air across srn Michigan, supporting respectable downdraft
CAPE. This and 0-6km bulk shear values near 30 knots will warrant
the mention of isolated strong/severe storms with any deep
convection that is able to initiate today. Wind gusts over 50 MPH
and small hail will be the primary risk with any robust convection
should it materialize.

There has been reasonable model consistency in upscale growth of
convection into a forward propagating MCS across the nrn
plains/upper Mid Mississippi Valley and wrn Great Lakes tonight. Model
solutions generally suggest this complex weakening prior to it
reaching Lake Michigan late tonight as it outpaces the better low
level forcing. Nonetheless, there is general model support showing
this complex developing a pronounced MCV, forecast to impact Se Mi
on Tuesday. With model solutions suggesting a decent CAPE gradient
across the forecast area, another chance of thunderstorms seems
warranted despite model solutions being rather lean on convection at
the moment. Heat and humidity are likely to affect the area again on
Tuesday, predicated on either limited convection or convective
development occurring later in the day. Given this uncertainty, the
heat advisory will not be carried into Tuesday at this time.

The well advertised pattern shift late in the week will feature long
wave troughing enveloping eastern Canada. An associated cold front
will be driven across srn Lower Mi Wednesday as Canadian high
pressure expands across the Great Lakes region from the north. This
will bring cooler and much drier conditions to the forecast area for
the latter half of the week.

MARINE...

Winds are out of the southwest this morning as high pressure drifts
into Ontario. Meanwhile, low pressure tracks north of Lake Superior
and drags a cold front across the northern Great Lakes this
afternoon. In addition to shifting winds to the northwest, this
front will also bring a low chance for a shower or thunderstorm over
Lake Huron. More widespread chances for showers and thunderstorms
arrive Tuesday as an upper level disturbance glances overhead. By
mid-week, a more pronounced cold front drops in from Ontario which
ensures a northerly component to the flow for the rest of the week.
No major marine concerns expected although wave heights will
increase with the shift to onshore flow. High pressure then slides
in from Canada late week into the weekend to support a period of dry
weather.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory from 10 AM this morning to 10 PM EDT this evening for
MIZ047>049-053>055-060>063-068>070-075-076-082-083.

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

$$

AVIATION.....KDK
DISCUSSION...SC
MARINE.......MV


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