506
FXUS63 KDTX 070358
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1158 PM EDT Sun Jul 6 2025

.KEY MESSAGES...

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

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

&&

.AVIATION...

The cold front has settled south of MBS and is set to pass FNT at or
soon after forecast issuance. A definitive northerly wind shift and
onset of IFR ceiling are the tracers on north to south progress
through SE Mi. The 500 mb trough trails the surface front just
enough to support a stray shower along and shortly behind the front.
Upstream ceiling observations across northern Lower Mi are solidly
IFR which adds confidence to the late night forecast as the front
moves slowly but steadily south to DTW before sunrise. IFR to MVFR
ceiling then holds for several hours during the morning until
breaking out into broken VFR coverage for the afternoon. Light
northerly wind continues through the day as high pressure gradually
assumes control into Monday evening.

For DTW/D21 Convection... There is lingering low probability for
thunderstorms late tonight as a cold front approaches from the north
and moves through the D21/DTW airspace before sunrise.

THRESHOLD PROBABILITIES...

* Low for thunderstorms late tonight.

* High for ceiling 5000 ft or less late tonight and through the
  morning.

&&

.PREV DISCUSSION...
Issued at 303 PM EDT Sun Jul 6 2025

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.

&&

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

$$

AVIATION.....BT
DISCUSSION...KGK
MARINE.......SF
HYDROLOGY....KGK


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