913
FXUS63 KDTX 060952
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
552 AM EDT Sun Jul 6 2025

.KEY MESSAGES...

- Hot and muggy conditions persist today.

- Showers and thunderstorms move in from the northwest today with
potential for torrential rainfall and isolated marginally severe
wind gusts during the afternoon and evening hours.

- Drier, a bit cooler, and less humid with time Monday and Tuesday.

- Shower and storm potential return mid-late week.

&&

.AVIATION...

VFR warm sector conditions remain in place over SE MI early this
morning as a cold front extends from the Straits to southern WI.
Prevailing southwest wind spreads in increasing moisture today,
resulting in a flare-up of diurnal cumulus and potential for an
isolated shower or storm prior to noon. The main forecast focus is
on increasing coverage of showers and storms during the afternoon
and evening as the cold front eases eastward into the local area.
Storms will be relatively disorganized early but may form into a
broken line by late afternoon, capable of isolated downbursts and
localized heavy rainfall. Convective vigor wanes after 01z with the
loss of daytime instability, but the front will continue to act as a
focus for additional scattered convection into the early overnight
period as it slowly progresses across the Metro Detroit sites.
Mainly MVFR conditions expected with dips to IFR or LIFR within
heavier convection. Post-frontal northerly wind maintains low
ceilings overnight into Monday morning with moderate confidence to
reach IFR at some sites.

For DTW/D21 Convection...Convective development becomes most
probable in the airspace after 18z. Confidence peaks within a 21z to
02z window when models depict a broken line approaching DTW from the
west. Instability lingers overnight offering a low probability for
additional scattered convection until FROPA occurs between 08z and
11z, marked by a wind shift to the north.

THRESHOLD PROBABILITIES...

* Low for thunderstorms this morning and early afternoon, then
  moderate mid afternoon into evening.

* Low for ceiling 5000 ft or less this morning, then high this
  afternoon through early Monday morning.

&&

.PREV DISCUSSION...
Issued at 304 AM EDT Sun Jul 6 2025

DISCUSSION...

Prototypical early July heat and humidity entrenched locally early
this morning, fortified by light southerly flow beneath lingering
lower amplitude ridging. General stability likely to hold through
the morning period as daytime heating gains traction, with attention
focused on an inbound elongated mid level trough and associated weak
cold frontal boundary. Notable increase in both forced ascent and
moisture quality as these features arrive from northwest to
southeast coincident with peak heating. This will serve as the focus
for a scattered to numerous coverage of showers and thunderstorms to
emerge during the afternoon and evening hours. Prospective mlcape
peaking in excess of 1500 J/kg supportive of some healthier
updrafts. Rather muted deep layer wind field inherent within this
summer pattern will offer some limitation to potential convective
organization overall, but an isolated damaging wind gust threat will
exist as the elevated PW content encourages greater precipitation
loading and wet microbursts within any deeper updrafts. Slow storm
motion also brings potential for localized regions of torrential
rainfall. Peak afternoon temps ranging from mid 80s north to around
90 degrees south. Gradual decline in convective potential with time
tonight, although lower end chances remain as the slow moving front
continues to engage a moist and weakly unstable profile. These
conditions persist into Monday morning before the front clears the
region to the south.

Increasing influence of high pressure centered to the north for the
latter half of Monday. After any lingering early day showers exit,
looking at notably less humid conditions with a modest reduction in
temperature with this post-frontal airmass change. This lends to
highs ranging from mid 70s to lower 80s. Maintenance of deep layer
stability held within existing surface ridging and generally zonal
mid level flow means benign conditions with standard airmass
modification Tuesday. Dry with seasonable temperatures overall this
period.

Another lower amplitude mid level wave likely to induce modest
height falls as it traverses the great lakes within the Wed-Thu
window. Defined sources of upward vertical motion relative to the
diurnal heating cycle remain ill-defined at stage. However, some
degree of troughiness even absent of more meaningful forced ascent
will establish a background environment supportive of convective
potential with a focus on the typical peak heating period. Outgoing
forecast continues to highlight a broader precip mention across this
entire period as offered by NBM output at this stage. Conditions
otherwise marked as seasonable by July standards through the latter
half of the week.

MARINE...

Low pressure will continue to move across the northern Lakes today.
The strengthening southwest winds are expected to continue through
about mid morning with the strongest gusts, around 20kts, occuring
over the central portions of Lake Huron. Due to shoreline effects,
the Saginaw Bay continues to have the potential to reach/exceed
25kts through mid morning today with waves approaching 3-4ft. The
Small Craft Advisory will expire at 10 a.m. and expect that to work
well as winds decrease around that time.

A cold front sagging south from the aforementioned low gradually
crosses Lower MI today. In advance, scattered to numerous showers
and storms are expected. Severe storms not generally expected
however an isolated strong storm can`t be ruled out. Behind the
front, mainly for Sunday night and Monday, northerly winds may
increase a bit for the Saginaw Bay and southern Lake Huron basin
with some gusts to 20kts. A few showers/storms look to linger into
Monday for the southern Great Lakes as the front is slow to fully
vacate. High pressure then briefly follows late Monday through
Tuesday before unsettled weather returns midweek.

HYDROLOGY...

Scattered to numerous thunderstorms are forecast this afternoon and
evening amidst hot and humid conditions. Thunderstorms will move
rather slowly and be capable of producing torrential downpours.
Localized areas may experience over an inch of rainfall in less than
an hour which may lead to flooding of urban areas, small streams,
and otherwise poorly drained areas. The main threat for flooding
will be between 3 PM and 9 PM, until the supporting cold front exits
toward the southeast.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 AM EDT this morning for LHZ421-422.

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

$$

AVIATION.....TF
DISCUSSION...MR
MARINE.......MR
HYDROLOGY....KGK


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at www.weather.gov/detroit.