453
FXUS63 KDTX 071955
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
355 PM EDT Mon Jul 7 2025

.KEY MESSAGES...

- Decreasing clouds with below normal temperatures in the mid to
  upper 70s this evening.

- Dry and seasonable conditions Tuesday.

- Shower and thunderstorm potential returns Tuesday evening and
  Wednesday with temperatures trending toward normal.

- Severe weather is not anticipated with the mid-week activity.

&&

.DISCUSSION...

Cyclonic flow lingers behind the surface trough this afternoon,
generating mostly cloudy skies over SE Michigan. Despite isentropic
downglide aloft and early July daytime heating, cooler northerly
flow off of Lake Michigan and Lake Huron has delayed the erosion of
this cloud deck compared to model solutions. That said, a scattering
trend is noted in GOES-16 visible satellite imagery off to the west
which will continue through the evening to support clearing skies.
Cold advection has brought H8 temperatures down to 12 to 13 C across
the cwa, which in combination with the stratus deck this morning has
generally capped temperatures in the upper 60s to low 70s.

The thermal trough slides overhead tonight, marking today as the
coolest day of the week. Weakening high pressure then briefly fills
in Tuesday morning, although SE Michigan remains in the basal
portion of the upper level trough. Clearly defined circulation on WV
imagery located in SE Saskatchewan reflects a closed 925-700mb low
that will track into Lake Superior Tuesday afternoon, occluding in
the process. As the system negatively tilts, this sends a warm front
into lower Michigan Tuesday evening with the warm sector
destabilizing profiles enough to trigger scattered convection as the
pre-frontal trough tracks through. Ascent will be reinforced in the
background by broad height falls and low level moist isentropic
ascent. MUCAPE values are not all that impressive, under 500 J/kg
per the SPC HREF, with mid level lapse rates around 5.5 C/km. For
any thunderstorms that do develop, storm organization will be
minimal as mid-level flow holds below 30 knots. So generally looking
at ordinary summertime convection that lingers into the overnight
hours.

The low will slowly drift east on Wednesday, with the atmosphere
eventually becoming capped in the mid-levels as the dry slot streams
in overhead. Although the general trend will be towards column
stability, the speed at which this occurs is still in question and
will be a deciding factor for whether additional thunderstorms are
possible Wednesday afternoon. The NBM gridded forecast latches on to
the slower solutions which do not bring in the dry slot until
Wednesday night, leaving the door open for additional convection
Wednesday afternoon in the leftover cyclonic flow. Drier conditions
are then anticipated Thursday and Friday with mid-level heights
amplifying across the region. Column thickness remains relatively
consistent through the period, keeping temperatures right around
normal in the mid-80s through the work week. Any fluctations will be
the result of diabatic influences like cloud cover and/or
convection. Unsettled conditions then arrive this weekend as a
Pacific wave pivots across central CONUS.

&&

.MARINE...

Axis of remaining showers (and infrequent lightning) will continue
to drift further east across Lake Erie through the early evening
hours as high pressure delivers continental Canadian air via
northerly gradient flow. Latest observations show afternoon speeds
are rather light, generally AOB 10 knots with sub-20 knot gusts.
Winds decrease further overnight, becoming more variable into
Tuesday as the surface pressure field trends more diffuse. Favorable
marine conditions are expected through Tuesday evening before the
next low pressure system drags a cold front across Lower Michigan.
Winds then organize out of the ESE, ahead of the surface low, with a
tightening gradient. Expect a period of showers and thunderstorms
within a pre-frontal warm sector for the southern waterways and
activity along the cold front further north, moreso for Lake Huron.
Ambient dynamics are rather weak which should keep prevailing
conditions below Small Craft Advisory criteria, but locally higher
winds/waves are possible with some stronger storms. Additional
isolated to scattered convection is possible Thursday, particularly
south of Lake Huron.

&&

.PREV DISCUSSION...
Issued at 204 PM EDT Mon Jul 7 2025

AVIATION...

Post frontal stratus has held through the morning and into the
afternoon with MVFR still widespread across the region. Daytime
heating has been able to mix out the last of the IFR and we should
see continued improvement through the afternoon into low VFR. High
pressure building in from the north will help scour out the
remaining clouds this evening with mainly a few/sct cirrus possible
later tonight. Northerly winds will decrease to less than 5 knots
tonight while veering around through the east to become southerly
Tuesday morning.

For DTW/D21 Convection...Thunderstorms are not forecast today into
tonight.

THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less this afternoon, then low this
  evening.


&&

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

$$

DISCUSSION...MV
MARINE.......KGK
AVIATION.....DRK


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