717
FXUS63 KDTX 080956
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
556 AM EDT Tue Jul 8 2025

.KEY MESSAGES...

- Dry and seasonable conditions today.

- More humid conditions return tonight and Wednesday, bringing an
increasing potential for showers and thunderstorms. Severe weather
is not anticipated with this activity, but locally heavy rainfall
and gusty winds are possible.

- Lesser potential for showers and thunderstorms Thursday as drier
air works back into the region. Dry and warmer conditions then
expected Friday.

&&

.AVIATION...

High pressure dominates the forecast through the daylight hours with
prevailing VFR conditions and light wind. Calm conditions and
saturated surface layer is leading to pockets of MVFR fog and low
cloud early this morning - this will disperse rapidly over the next
few hours as mixing ensues. As the center of high pressure begins to
exit east this afternoon, sufficient moisture return supports a SCT
diurnal cumulus field. A weak disturbance working across the western
Great Lakes brings potential for a stray shower west of US-23 this
evening, then increasing chances for scattered showers and perhaps a
few rumbles of thunder after midnight within an increasingly
unstable environment. Low confidence exists for timing of any
nocturnal convection within the poorly forced setup, so will
continue to highlight with PROB30 at this time.

For DTW/D21 Convection... No convection through the daylight hours
today. Low confidence on timing and occurrence of showers/storms in
the vicinity mainly after 06z Wednesday.

THRESHOLD PROBABILITIES...

* Low for thunderstorms after midnight into Wednesday morning.

&&

.PREV DISCUSSION...
Issued at 343 AM EDT Tue Jul 8 2025

DISCUSSION...

Lower amplitude westerly flow to govern conditions through this
afternoon. General mid level subsidence atop pervasive surface high
pressure will maintain a high degree of deep layer stability and
corresponding benign conditions. Limited moisture quality throughout
the column ensures high insolation potential, lending a boost to an
already moderating thermal profile off the notably colder readings
from yesterday. Afternoon readings back to around early July norms -
highs low to mid 80s. Minor shortwave energy lifting through the
mean flow will offer some reduction in mid level heights beginning
tonight. This process will draw a weak warm front through the region,
while establishing a period of greater moisture advection overnight.
Signal remains across the model spectrum for associated ascent to
prove sufficient in generating some widely scattered nocturnal
showers and thunderstorms across the lower peninsula. A more focused,
higher probability of precipitation could materialize by late
tonight/Wed morning should a greater corridor of dcva emerge tied to
a passing pv feature.

Broad lower amplitude mid level troughing established for the
Wednesday period, as the main height fall center/closed low pivots
across Ontario. Trailing surface trough arrives for the daylight
period and offers a primary focus for additional convective
development. Early day cloud/shower potential could dampen the pace
of diurnal destabilization for at least a portion of the area, while
also potentially establishing a greater differential heating
boundary to provide an additional focus. In general, a modest level
of instability projected. This in combination with a lack of a
greater wind field suggests simply garden variety activity. The
elevated moisture content again brings potential for any water loaded
updrafts to generate locally higher rainfall rates and gusty winds
during the afternoon and evening.

Weakly cyclonic mid level flow will persist into Thursday. A
potential transition day as drier air upstream attempts to arrive
during the daylight period as northwest flow emerges upon exit of
low level troughing. Mixed signal yet regarding pace of this
process, thus leaving the door open for east/southeast sections to
maintain an adequately moist and weakly unstable environment to
support a lower end chance of convective development. Further
revision of rain chances likely this period. Greater stability as
low to mid level ridging arrives lends to higher confidence for dry
conditions Friday. Corresponding increase in mean thicknesses would
also support a modest warming trend to finish the week. Conditions
appear more unsettled for at least a portion of the weekend period,
as a more dynamic wave projects to lift across the great lakes.
Scattered to numerous showers and thunderstorms already highlighted
by latest NBM output for Saturday.

MARINE...

Light and variable winds to start as the surface pressure field
trends more diffuse. Favorable marine conditions are expected until
the overnight hours as 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.

HYDROLOGY...

Scattered to numerous showers and thunderstorms are forecast
Wednesday. Storms will be relatively disorganized, but with humid
conditions and slow storm movement, storms will be capable of
producing torrential downpours. Localized areas may receive over 1
inch per hour, which may lead to flooding of urban areas, small
streams, and otherwise poorly drained areas. The main threat for
flooding will be between 1pm and 8pm.

&&

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

$$

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


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