074
FXUS63 KDTX 152357
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
757 PM EDT Mon Jul 15 2024

.KEY MESSAGES...

* A strong line of thunderstorms will cross SE MI around and after
  midnight tonight. Scattered damaging wind gusts will be possible
  mainly south of I-69.

* Heavy rainfall is likely with these storms potentially leading to
  areas of flooding particularly in urban areas. A Flood Watch is in
  effect for the M-59 and I-94 counties.

* A slow moving cold front keeps scattered showers and non-severe
  thunderstorms in the forecast for Tuesday. A few afternoon showers
  also possible Wednesday afternoon as a cooler airmass settles in.

* High pressure brings cooler and less humid weather into the region
  for the late week period.

&&

.AVIATION...

VFR skies with a southwest wind to 10 knots will carry through the
early portion of the night. An upstream thunderstorm complex is
taking shape over Iowa and will move through southern Wisconsin and
northern Illinois this evening. System will track east into a
somewhat favorable environment across southeast Michigan for
maintenance of thunderstorm activity. Timing of activity through
southeast Michigan remains between 05Z and 10Z. Ceilings during this
time will be borderline VFR/MVFR with MVFR to IFR likely from heavy
rainfall with the thunderstorms. Lower clouds look to linger
throughout tomorrow morning in the wake of the complex with a gradual
lifting of ceilings throughout the day. Winds become more westerly
to around 10 knots for tomorrow afternoon.

For DTW/D21 Convection...Models continue to point towards
thunderstorm timing between 06-09Z tonight. Subtle adjustment by an
hour remains possible if any activity pops up ahead of the inbound
complex. Strong winds, lightning, and heavy rainfall are all
possible hazards with this system.

DTW THRESHOLD PROBABILITIES...

* Medium for thunderstorms tonight.

* Medium for ceilings aob 5,000 early tomorrow morning.

&&

.PREV DISCUSSION...
Issued at 308 PM EDT Mon Jul 15 2024

DISCUSSION...

Active subsidence in the wake of this morning`s MCV has led to
mostly sunny-partly cloudy skies this afternoon supporting a
respectable temperature rebound back into the mid 80s for most areas
as well as a few upper 80s. For the rest of the evening, muggy but
dry conditions hold before another round of thunderstorms arrives
overnight.

A shortwave trough digging into the northern Plains helps spur the
development of convection along the stalled cold frontal boundary
currently draped over the upper Midwest. This convection will
quickly grow upscale into a mature MCS by the time it reaches the
western Great Lakes/northern Ohio Valley late this evening/early
tonight. Arrival timing for SE MI will be around and after midnight
falling within the diurnal instability minima. That said, CAMs still
suggest several hundred to around 1300 J/kg of SBCAPE will be
available over the area, focused south of I-69, which should be more
than sufficient to maintain this line all the way through the CWA
(albeit with a gradual weakening trend). Storm mode favors damaging
wind gusts as the primary severe threat with best potential south of
I-69 given favored track of the line over northern IN/southern lower
MI and forecast soundings showing around 1000 J/kg of DCAPE locally;
currently these areas are highlighted by a Slight Risk from SPC.

In addition to the aforementioned severe threats, heavy rain and
flooding will be a hazard with these storms. Humid airmass currently
in place will be reinforced by a nocturnal southwest LLJ feeding
moisture into southern lower MI pushing PW values near 2". While the
progressive nature of the line should help to reduce residence time
over any single location, given the magnitude of moisture within
this airmass, warm cloud layers between 13-15kft, and wet recent
pattern including this morning with areas along/just north of M-59
picking up a quick 1-4 inches of rain, have opted to issue a Flood
Watch for the M-59 and I-94 counties- mainly for urban flooding
potential.

Parent cold front still looking to stall out over the southern half
of the area (roughly south of a Sandusky-Flint line) Tuesday. This
becomes the focal point for renewed scattered shower and non-severe
storm chances through the early evening with diurnal instability
climbs back near 1000 J/kg. Front is eventually forced east of the
region by late Tuesday evening as the upper trough drops into the
northern Great Lakes. Said trough slides across the central Great
Lakes mid to late week bringing with it a much cooler, drier
airmass. 850mb temps drop to 5-8C (down from 15-17C) and surface
dewpoints fall back into the 60s and eventually 50s late week. Can`t
rule out a couple (thunder)showers Wednesday afternoon-early evening
as CAA aloft modestly steepens lapse rates and a secondary cold
front sweeps through. Surface high pressure builds in by Thursday
before drifting overhead through Saturday supporting sunnier,
pleasant conditions to close out the week.

MARINE...

Benign marine conditions are expected for the remaining daylight
hours before a line of strong to possibly severe thunderstorms
impacts areas south of Saginaw Bay after midnight tonight (04z). The
system will be well-defined before reaching the area but may weaken
some given the overnight timing. This is not a guarantee given the
warm and unstable airmass that is in place, so boaters should be
prepared for wind gusts to 50 knots, large hail to an inch, and
heavy rainfall with rates up to an inch per hour through at least
daybreak Tuesday. The thunderstorm complex exits the area by 12z or
so, although storm-scale pressure perturbations may produce gusty
winds up to 30 knots (as seen with the MCS this morning) and
elevated wave heights even after precipitation ends. A short-fused
Small Craft Advisory is possible Tuesday morning. Chances for
showers and storms then continue through Tuesday evening as a cold
front slowly drifts across the area, eventually veering winds to the
NW. Cooler and showery conditions expected Wednesday as an upper low
approaches the Great Lakes which will govern conditions through the
mid week period.

HYDROLOGY...

Another round of thunderstorms are set to arrive tonight, around and
after midnight. Humid airmass remains in place and is likely further
reinforced ahead of this line of storms. As a result heavy rainfall
is expected with these storms with rainfall rates in excess of 1
inch per hour. While the progressive nature of the line should help
limit residence time over any one location, this humid airmass
combined with the recent wet pattern (including the 1-4 inches that
fell this morning near M-59) offers the potential for flood concerns
mainly across the urban footprints as a quick 1-2" of rainfall is
possible. As a result, a Flood Watch has been issued for the M-59
and I-94 counties tonight.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch from midnight EDT tonight through Tuesday morning for
     MIZ068>070-075-076.

Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....AA
DISCUSSION...KDK
MARINE.......MV
HYDROLOGY....KDK


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