825
FXUS63 KDTX 100947
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
547 AM EDT Thu Jul 10 2025

.KEY MESSAGES...

- Trending warmer through the rest of the week, with heat index into
the mid to upper 90s on Saturday.

- Increasing potential for showers and storms on Friday and Saturday
with isolated severe storms and heavy rainfall possible each day.

- Drier conditions favored Sunday into early next week.

&&

.AVIATION...

A moist near surface environment combined with calm wind
contributing to some areas of fog and/or very low stratus this
morning. Any lingering restrictive condition will rapidly lift as
daytime heating gains traction through 13z. Otherwise, a drier
environment will remain entrenched today. Outside shot for an
isolated shower or thunderstorm this afternoon. Wind will remains
light today, with a general direction from the west to northwest.

For DTW/D21 Convection...Chance of thunderstorms this afternoon
remains at less than 20 percent.

THRESHOLD PROBABILITIES...

* Low for an isolated thunderstorm this afternoon.

&&

.PREV DISCUSSION...
Issued at 431 AM EDT Thu Jul 10 2025

DISCUSSION...

Confluent northwest upper flow within a background rising height
field maintains subsident conditions and an overall stable profile
today. Recent rainfall, calm wind, and clear sky overnight were
favorable conditions for patchy fog development this morning - this
will stick around through sunrise before the July sun mixes out the
saturated surface layer. Meanwhile, high pressure building across
the Great Lakes is producing northeast surface wind off Lake Huron
which has led to an inland push of stratus beneath the inversion.
These clouds should likewise mix into a scattered coverage of
cumulus this afternoon. Yesterday`s low pressure and cold front
weakened and washed out over the region - this will maintain an
instability gradient in the vicinity through the day. Models
continue to suggest that this, with a boost from convergence along
lake breeze boundaries, will be sufficient to overcome the weak cap
and trigger a few isolated showers this afternoon. Otherwise most
areas stay dry with partly cloudy skies and highs in the lower to
mid 80s.

The Friday forecast continues to carry a high degree of uncertainty,
even 24 hours out, as it will be sensitive to the development,
track, and strength of upstream MCS activity. The ambient
environment will be characterized by low amplitude ridging leading
to modest height rises through the day. This favors weakly stable
conditions absent of forcing mechanism. Embedded in the relatively
weak flow beneath the ridge will be several shortwaves originating
from ongoing convection over the upper Midwest. The bulk of
available CAMs have a similar flavor depicting an MCS emerging out
of the MN/WI/IL region tonight and tracking across Lake Michigan
early Friday morning. This activity is likely to weaken by the time
it reaches mid MI shortly after diurnal minimum, but it still
suppresses heights to weaken the cap and lays out an outflow
boundary that then serves as a focus for convective initiation later
in the afternoon. The strength of the wave will dictate how much
moisture and instability is advected into SE MI through the first
half of the day, and how much wind shear is available for storms to
utilize. SPC introduced a Marginal Risk into the area for the threat
of damaging wind gusts should this scenario play out. Heavy rain
will also be a threat given PWAT rising back up to the 1.75 to 2.00"
range. The latest HREF places a 3+" bullseye over Metro Detroit
which is a signal worth monitoring. Another plausible scenario would
be that a morning MCS stifles instability recovery and mitigates
severe/heavy rain threat later in the day. Will have time to refine
the forecast as upstream convective trends are evaluated, but for
now have increased PoPs across the area on Friday. The thermal
trough in place today will gradually ease out on Friday, with high
temps taking a step upward into the mid 80s to around 90. These may
be slightly suppressed should a cloudier scenario play out.

Saturday is likely to be the warmest day of the week as deep
southwest flow sets up ahead of an amplified upper wave emerging out
of the Canadian Prairie. Latest guidance places 850mb temp in the 18
to 19 C range which supports highs in the lower 90s and heat index
in the mid to upper 90s. Convective trends remain a focus as the
wave moves in and takes on a negative tilt over the upper Great
Lakes Saturday night. The cold front looks to arrive overnight, but
the weakly capped environment and a prefrontal trough look to
support convective initiation during peak heating with increasing
support from ascent via right entrance jet streak dynamics.
Magnitude of wind shear may be a mitigating factor for severe
potential as the better jet core passes north of us and not until
overnight. SPC introduced a Marginal Risk for severe weather on
Saturday as well.

Relatively cooler weather on Sunday in the wake of the cold front,
but then temperatures are likely to trend back toward above normal
values early next week as the next ridge builds in from the south,
sending 850mb temps back into the upper teens C. High pressure keeps
the forecast mostly dry early in the week but then chances for
showers and storms increase midweek as the ridge breaks down.

MARINE...

High pressure to bring tranquil conditions and calm to light winds
today through tomorrow. South to southwesterly flow will be
reinforced Friday into Saturday as high pressure departs and washes
out across New England. The next chance for showers and
thunderstorms will return this weekend ahead and along a cold front.
The strengthening pressure gradient ahead of the front will bring
the potential to see non thunderstorm gusts around 20 knots, with
localized higher gust potential with any stronger showers and
storms.

HYDROLOGY...

The next period to monitor for potential heavy showers and storms is
Friday and Saturday as a hot and humid air mass builds back into the
region. The forecast for Friday carries a lot of uncertainty at this
stage, but there is the potential for a thunderstorm complex to
arrive from the west early in the day and act as a trigger for
afternoon showers and storms. If this occurs, the environment would
support heavy downpours with rainfall rates in excess of 1 inch per
hour and slow storm motions leading to localized flooding concerns.
Saturday presents a higher likelihood for showers and storms with a
similar environment also supportive of a localized flooding risk.

&&

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

$$

AVIATION.....MR
DISCUSSION...TF
MARINE.......AM
HYDROLOGY....TF


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