910
FXUS63 KDTX 050353
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1153 PM EDT Fri Jul 4 2025

.KEY MESSAGES...

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

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

&&

.AVIATION...

Warm and humid air is now fully in place across SE Mi after northern
Ontario low pressure pulled the warm front into northern Lower Mi.
Ground based firework smoke/haze mixed with fog take a few hours to
dissipate within the humid surface based stable layer. Calm to light
south wind increases slightly toward sunrise to aid in that process
and solidify warm sector VFR through the morning. Warm and humid air
remains in place in the afternoon to fuel scattered to broken cumulus
development. Thunderstorms are held off by a capping 500 mb ridge
through Saturday evening.

For DTW/D21 Convection... Thunderstorms are not forecast for the
rest of tonight and Saturday.

THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 345 PM EDT Fri Jul 4 2025

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.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.

Lake Huron...Small Craft Advisory from 2 PM Saturday to 10 AM EDT Sunday for
     LHZ421-422.

Lake St Clair...None.

Michigan waters of Lake Erie...None.

&&

$$

AVIATION.....BT
DISCUSSION...AA
MARINE.......KDK


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