966
FXUS63 KDTX 061903
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
303 PM EDT Sun Jul 6 2025

.KEY MESSAGES...

- Hot, muggy, and breezy conditions preclude increasing showers and
  thunderstorms with potential for isolated marginally severe wind
  gusts and torrential rainfall through the evening hours.

- Becoming drier, cooler, and less humid with time Monday and
  Tuesday.

- Shower and storm potential returns mid-late week with temperatures
  trending above normal.

&&

.DISCUSSION...

Denser cloud field gradually expands eastward across Southeast
Michigan, ahead of a slow moving cold front bringing increasing
coverage of showers and thunderstorms through the evening hours. Out
ahead of this boundary, SSW winds reinforce a hot, muggy, and breezy
airmass marked by dewpoints near 70F. Differential heating yields
spatial differences in the distribution of peak instability as
several showers and thunderstorms have already developed along the
instability gradient where better shear is present. Some of the
updrafts have been productive, featuring overshooting tops near
minus 60C.

Synoptic ascent associated low amplitude troughing aloft aids in the
expansion of storm coverage with time as MLCAPE responds, but the
underwhelming shear profiles still preclude widespread severe
considerations. Main concern remains focused on the immense influx
of pre-frontal water vapor which leads to the doubling of PWATs (see
06.12Z KGRB and KAPX RAOBs), compared to the 06.12Z KDTX RAOB (1.03
inches). This presents an isolated/marginal severe wind threat due
to the potential for wet microbursts, in addition to some flooding
for areas that might experience repeat torrential rainfall.
Convective environment will be less favorable into Metro Detroit,
located well ahead of the lagged frontal forcing, and displaced off
the main instability axis. Certain CAM solutions suggest that
activity could undergo rapid decay upon reaching the population
center, especially if it takes until closer to sunset for the
loosely organized cells to arrive.

Higher uncertainty in precipitation potential exists during the
overnight hours as the front`s progress further slows. While a
signal for a reduction in coverage and intensity after dark is well
advertised in the model data, the persistence of nocturnal
instability, coincident with the frontal slope, supports pulse
thunderstorms overnight. Progs show the anticipated wind shift and
surface trough axis still not necessarily clearing the forecast area
by 06Z. Pervasive post-frontal status spills in tonight which limits
efficiency of nocturnal cooling and undercuts the advection of
continental Canadian air, once surface flow veers northerly.

Column moisture stays quite elevated Monday morning for areas south
of I-96/I-696 with forecast soundings also showing minimal
adjustments to thermodynamic profiles. This preserves some degree of
instability for a few additional thundershowers until tropospheric
winds shift westerly, drying out the mid-levels. Monday will be the
coolest day of the week with highs running a couple degrees below
normal. Expect upper 70s to near 80F for most, inland of the cooler
Huron lakeshore. The cold front then stalls, becoming a stationary
boundary locked in over the northern Ohio Valley as surface high
pressure builds into the Great Lakes through Tuesday. This ensures a
24+ hour period of drier weather.

Trough amplification takes place over the region Wednesday into
Thursday, extending from a PV anomaly over Ontario that leads to the
wave closing off as it crosses into western Quebec. Southerly flow
sends the warmer stalled airmass over Ohio back toward southern
Lower Michigan. This provides fuel for the next phase of diurnally
driven summertime convection. Dewpoints also tick higher, perhaps
back above 70F with vicinity upper-level divergence offering
opportunities for some more robust updrafts. Shortwave ridging moves
in Friday with low-end precipitation potential driven by MCS
remnants from The Plains.

&&

.MARINE...

A slow moving cold front will move through the Central Great Lakes
tonight, triggering numerous showers and storms this evening. Some
of the storms may be strong, producing torrential rainfall and wind
gusts of 45-50 knots. Behind the front, northerly winds look to top
out around 20 knots over Lake Huron on Monday. Waves impacting the
nearshore waters of southern Lake Huron still look to be mainly
below 4 feet however. A few showers/storms could linger over Lake
Erie into Monday before enough dry low level air works in toward the
southern Michigan border.

High pressure then briefly follows late Monday through Tuesday
before unsettled weather returns midweek, with a chance of showers
and thunderstorms. Even so, outside of any short lived storms, winds
look to be light under 20 knots.

&&

.HYDROLOGY...

Thunderstorms continue to spread eastward this evening amidst hot
and humid conditions. Storms will move rather slowly and be capable
of producing torrential downpours. Rainfall rates in excess of an
inch per hour are expected, but will occur in localized fashion.
Narrow segments of ongoing storms have been sample by KDTX radar
with estimated rates in excess of 4 inches per hour. This may lead
to flooding over developed locations, small streams, and other areas
subject to poor drainage mechanisms. The main time-frame for
flooding will occur between 3 PM and 9 PM, until the supporting cold
front works further southeast. This lends a decreasing in intensity
and coverage of storms through the overnight hours. A few lingering
showers/storms are possible Monday morning, mainly south of the I-
96/I-696 corridor.

&&

.PREV DISCUSSION...
Issued at 126 PM EDT Sun Jul 6 2025

AVIATION...

Breezy southwest winds prevail ahead of a cold front progged to
slowly drop south across the area late tonight and into Monday
morning. Wind gusts at YIP/DTW/DET have been overachieving, given
the ample sunshine during the late morning/early afternoon hours.
Showers and storms have developed across portions of central and
western Michigan early this afternoon. These storms are expected to
move east-northeast across the area with additional development into
the evening hours. The environment is favorable for clusters of
storms with water loaded updrafts capable of producing stronger
outflow winds and heavy rain. Cannot rule out a microbursts or two
as well, especially if we get any stronger, elevated thunderstorm
cores.

Convection will wane in intensity and coverage around/after 02Z this
evening. The above mentioned cold front is progged drop through the
Tri-Cities and Thumb region between 00-02Z. With the front being
slow to clear the area tonight and into Monday morning, there will
be a linger chance for showers and a few isolated storms overnight.
The front moves into the MBS area between 00-02Z this evening,
helping spread northerly winds and MVFR to IFR stratus into the
area. FNT/PTK will see a similar wind shift and arrival of low
stratus between 03-06Z, and DTW/DET/YIP between 07-09Z. Northerly
winds will prevail behind the front. IFR stratus will gradually lift
into the MVFR category through late morning Monday as daytime
heating and mixing increase, then ceilings are expected to gradually
scatter out by early Monday afternoon.

For DTW/D21 Convection...Widely scattered convection is expected
this afternoon and evening, with the peak window for impacts across
the airspace between roughly 20Z and 02Z. For DTW, as showers/storms
move in from the west the main window of concern is 22Z and 02Z.
Isolated microbursts and gusty thunderstorm outflow winds will be
possible this evening with any stronger, more organized clusters of
storms. Lingering low probability for thunderstorms overnight
between 08-12Z, followed by a cold front passage and switch to north
winds.

THRESHOLD PROBABILITIES...

* Medium for thunderstorms between 22Z and 02Z this evening, the low
  overnight and into early Monday morning.

* High for ceiling below 5000 ft between 06Z and 18Z Monday.


&&

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

$$

DISCUSSION...KGK
MARINE.......SF
HYDROLOGY....KGK
AVIATION.....JA


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