907
FXUS63 KDTX 041945
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
345 PM EDT Fri Jul 4 2025

.KEY MESSAGES...

- Hot and muggy conditions through this weekend with highs in the
  upper 80s today and lower 90s Saturday into Sunday.

- Widely scattered showers and thunderstorms this afternoon roughly
  along and west of the I-75 corridor, then dry on Saturday.

- Next chance for better widespread showers and thunderstorms on
  Sunday, then drier with less humidity starting Monday.

&&

.DISCUSSION...

Upper ridge axis will move across the Mississippi River Valley today
leading to subtle mid level height rises locally into this evening.
Despite the rising height, shortwave energy riding the arriving
ridge in combination with a warm front draped NW to SE across
Michigan is enough to support the widely scattered showers and
thunderstorms this afternoon into the early portion of the evening.
Positioning of the front favors roughly along the I-75 corridor and
points west for the highest PoPs with the mean wind driving activity
NW to SE across this corridor. There will be at least several
hundred j/kg of MUCAPE available today, but with weak mid level
lapse rates. This along with effective shear to near 30 knots will
further support disorganized cells or clusters of cells. Severe
threat remains low, but the increasing low level lapse rates will
help support wind gusts to 40 mph or greater with any stronger
thunderstorms. Activity will wane by towards sunset with a warm and
mostly dry overnight period. Lows tonight drop only to about 70
degrees.

Greater heat and humidity push into southeast Michigan tomorrow
underneath the ridge as temperatures at 925 mb top 20C. Daytime
highs are expected to exceed 90 degrees with dew points pushing 70
degrees. The elevated dew points will help push heat index values
into the mid 90s for tomorrow afternoon. Saturday should remain
mostly dry as more stable conditions under the ridge arrive.

The next chance for precipitation will come late Sunday morning
through the afternoon as a mid level wave and associated cold front.
Instability will bring a chance for thunderstorms but weak mid-level
lapse rates and weak shear precludes any severe potential at this
time, but strong storms may be possible with as current frontal timing
appears to be favorable in the peak heating time frame.

High pressure will follow the frontal passage along with lower
humidity values for Monday and through the early week. Summer time
high temperatures will remain though with high temperatures holding
around normal in the lower/mid 80s. The next chance for
precipitation in the forecast will be mid-week as a mid level wave
tracks across the central plains and across the southern Great
Lakes.

&&

.MARINE...

Low pressure ejecting out of the northern Plains leads to a
tightening of the local gradient and strengthening southwest winds
Saturday. Strongest gusts, around 20kts, are expected over the
central portions of Lake Huron. Due to shoreline effects, the
Saginaw Bay has the potential to reach/exceed 25kts Saturday
afternoon-evening with waves, particularly in the outer portions of
the Bay, being able to approach 3-5ft. While borderline to meet
Small Craft Criteria, given the holiday weekend and the rougher
waters even if winds/waves come up a bit short, Small Craft
Advisories are likely for these waters. Hot, humid airmass returns
to the region through the weekend ahead a cold front sagging south
from the aforementioned low sliding over the northern Great Lakes.
Scattered to numerous showers and storms are expected along the
front late Saturday night through Sunday as it crosses. A few
showers/storms look to linger into Monday for the southern Great
Lakes as the front is slow to fully vacate. High pressure then
briefly follows late Monday through Tuesday.

&&

.PREV DISCUSSION...
Issued at 1247 PM EDT Fri Jul 4 2025

AVIATION...

VFR conditions expected through the taf period, outside of any
thunderstorms. Moisture advection this afternoon over southeast
Michigan, coupled with the increased daytime instability, should be
sufficient for scattered showers and thunderstorms, but disorganized
nature will make for a difficult call on when and which taf(s) they
impact. As usual with the strong thunderstorms producing heavy
downpours, potential for vsby to drop into IFR for short period.
FNT/PTK appear to be in the best position to see activity, and will
carry tempo group and leave other sites with prob30, and just adjust
based on trends.

Looking at just some mid/high clouds around tonight as low level
southwest winds slowly increase. Instability appears low and low
level jet does not look strong enough to touch of additional
activity, but still a low chance as remnant MCV drops southeast from
western Great Lakes. Warming/drying in the mid levels tomorrow
expected to hinder thunderstorm activity, with southwest surface
winds increasing aoa 10 knots in the afternoon.

For DTW/D21 Convection...Good chance of an isolated thunderstorm or
two in the Detroit Metro Airspace this afternoon into early evening,
but low confidence in DTW getting hit directly.

THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less this afternoon and evening, and
  then again tomorrow morning.

* Low for thunderstorms into early evening hours..


&&

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

$$

DISCUSSION...AA
MARINE.......KDK
AVIATION.....SF


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