Expert Forecast Opinion

162
FXUS63 KDTX 301605
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1205 PM EDT Mon Jun 30 2025

.KEY MESSAGES...

- Warm and humid conditions today. Afternoon heat indices will be
near 90 degrees.

- Showers and thunderstorms are likely this afternoon and evening.
There is a Marginal Risk (1 out of 5) for severe weather 1pm to 7pm
across all of Southeast Michigan. The most likely threats will be
damaging wind gusts to 60 mph and flooding due to torrential
rainfall rates.

- Classic summer weather pattern during the middle to end of the
week with daytime temperatures well into the 80s.

&&

.AVIATION...

An influx of low and mid level moisture this morning has led to a
wide array in ceilings heights across Se Mi, with the metro Detroit
terminals experiencing periods of MVFR based ceilings. The gradual
departure of the higher cloud deck is opening the door to rapid
destabilization across Se Mi. This within a moist and uncapped
environment has led to numerous thunderstorms across wrn Lower Mi,
which will slowly develop and advance across Se Mi during the early
portion of the afternoon. Given the ongoing early convective
release, the probabilities of thunderstorms beyond 21Z is less
probable and will be left out of the TAFs. Given the potential
afternoon convection and abundant low level moisture, some degree of
low clouds may linger into the early evening hours before a little
bit of low level dry air advection clears them out.

For DTW/D21 Convection...The departure of the thicker morning cloud
cover is now driving the region of better instability into the metro
airspace. The combination of convective development and upstream
convection moving into the airspace will likely support scattered to
numerous thunderstorms through at least 20 or 21Z. The afternoon
convective release will make convection after 21-22Z less probable.

THRESHOLD PROBABILITIES...

* Moderate in thunderstorms this afternoon.

* Moderate in ceilings aob 5000 feet this afternoon.

&&

.PREV DISCUSSION...
Issued at 331 AM EDT Mon Jun 30 2025

DISCUSSION...

A myriad of subtle and weak forcing mechanisms will work together
today to yield a setup for synoptic ascent over all of Southeast
Michigan. The main influences throughout the next 36 hours will be
the positively tilted midlevel trough now tracking through the
northern Plain States and the 1000-500mb geopotential height falls
that will occur in advance. Latest model data supports a very broad
footprint to the height falls that are already expanding into the
forecast area early this morning. No surprise to see the uniform
south wind direction off of the deck in the DTX VAD wind profile.
First item of note is a diffuse 850-500mb warm front and system
relative 925-700mb weak cyclonic circulation that will lift into the
far southern forecast area between 09-15Z. Ragged shortwave energy
attendant to this warm front is forecasted to clip the Ohio
border/Lake Erie vicinity with some weak semblances of some brief
deformation forcing. The forecast is fairly quick with ramping up
Pops after 12Z and that seems adequate. Latest radar mosaic does
have Z returns lifting due northward towards Monroe County.

A broader axis of absolute vorticity will track northeastward across
and through Southeast Michigan today in the 12-00Z timeframe. Given
the d(vorticity)/dt tendency do think it will take a diabatic
heating contribution to enhance and invigorate the synoptic ascent
today. For this reason do think the greatest coverage of showers and
thunderstorms will be during the afternoon. Hires signal shows bulk
of the activity between 17z-23z. Rich boundary layer with modest
midlevel lapse rates will result in CAPE values of 2000-2500 J/kg
and little to no convective inhibition. Weak shear profiles will
result in pulse type to possibly some multicellular organization.
Main threat will be windgusts to 60 mph from heavy water loading and
wet microbursts. All of Southeast Michigan is in a Marginal
designation for severe weather today. Rich moisture in place always
brings a potential for torrential rainfall rates. Latest EPS
distribution shows 75th percentile at around 0.5 inch with some 90th
percentile tails up around 1.50 inch. So there is definitely some
members showing heavy rainfall potential, just not much from a large
picture perspective to suggest it will be widespread. If anything
the threats will come down to mesoscale features such as lake breeze
convergence boundary and or the collision of outflows. The greatest
signal out of the 00z HREF is in the Thumb. The day shift will have
the 12Z set of data to look over, but for now will recommend that
best approach is with short fuse warnings and advisories.

Northwesterly flow system relative isentropic descent will bring
subsidence and a modest lowering of humidity for the middle to end
of the week. More comfortable, but nonetheless, classic summer
weather conditions are anticipated. Looking at daytime highs in the
80s Tuesday through Friday (0 to 5 degrees above normal) with
dewpoints predominately in the 60s. There doesn`t appear to be much
potential for organized precipitation during middle to end of the
week period.

MARINE...

A cold front will trigger showers and and thunderstorms this
afternoon into the evening, with a embedded strong storms around.
Westerly post-frontal winds on Tuesday look to top out around 20
knots, but with offshore flow, small craft advisory does not seem
warranted.

High pressure over the Midwest for the mid week period, with weak
northwest gradient in place over the Great Lakes region looks to
support light winds and waves, right into Friday as the center of
the high pressure arrives.

&&

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

$$

AVIATION.....SC
DISCUSSION...CB
MARINE.......SF


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