216
FXUS63 KDTX 182321
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
721 PM EDT Tue Jun 18 2024

.KEY MESSAGES...

- Hot and humid conditions will persist across most of the area
through the week.

- Chances of thunderstorms will continue each day of the week. Some
of these storms may be strong to severe with locally heavy
downpours.

&&

.AVIATION...

There remains a few boundaries associated with the lake breeze and
outflow from earlier convection across Ohio that may still result in
a few isolated showers and storms for KDET/KDTW/KYIP this evening.
Will monitor those trends over the next few hours and provide
amendments if convection does materialize. Otherwise, the risk for
thunderstorms will continue to wane into the overnight hours and VFR
conditions are expected. Winds will remain generally from the
southwest, with the exception of more southerly winds as lake breeze
boundaries move through KDET/KDTW this evening and again Wednesday
afternoon/evening. Thunderstorms remain possible yet again on
Wednesday, especially during the afternoon and evening hours. There
is quite a bit of mid/high clouds to our south, which is expected to
lift northeast across southeast Michigan tomorrow. That is something
that we will need to keep an eye on, as mid/high clouds put a lid on
much of our convection today.

For DTW/D21 Convection...There are a few pockets of thundestorms
well north and south of KDTW. Lingering boundaries as noted above
may still result in the development of thundestorms near KDTW until
about 00Z tonight. Potential for wet microbursts lingers this
evening, should stronger storms develop over/near D21 airspace.
Additional convection remains possible for Wednesday, but confidence
is low regarding coverage. Any storms on Wednesday will be slow
moving and will still pose a threat for wet microbursts.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms until 01Z.

* Low for ceiling at or below 5000 ft, conditional with
  thunderstorms.

&&

.PREV DISCUSSION...
Issued at 353 PM EDT Tue Jun 18 2024

DISCUSSION...

Opaque mid cloud altostratus and haze associated with the shortwave
lifting into western Lower Michigan has been very effective in
dampening insolation through the noon hour. Have observed very
little boundary layer cumulus growth into the early afternoon hours
across Southeast Michigan. The real forecast challenge now heading
forward is what sort of low-midlevel convective inhibition will hold
on as forecast soundings were advertising the greatest projected
instability would exist at midday just prior to the deepest boundary
layer mixing. The most recent ACARS soundings do show a pronounced
stable layer residing in the 850-775mb layer that does match with
the forecast soundings (3.0 to 6.0 kft agl). Signal of the 18.12Z
CAMS was decidedly leaner with convective coverage over all of the
forecast area, although the MPAS runs and a couple of the WRF ARW
runs continue to show some development after 20Z. Small scale of the
modeled updrafts in the CAMS suggest a more muted UVV response and
for this reason the potential for strong to severe storms (if they
were to develop) is probably less than yesterday. Will leave PoPs in
the high chance category this afternoon given the convergence that
is expected to develop. Strong wind gusts from water loading/wet
downbursts are the main threat with heavy rainfall from any training
another possibility.

A ribbon of sheared absolute vorticity is expected to lift northward
along the periphery of the upper level ridging into the Great Lakes
region during the daytime Wednesday. Model data shows the strongest
shortwave center then impinging directly into the area during the
late afternoon. More transparency to the cloud and modest cooling in
the 850-700mb layer is expected to result in less low-mid CIN over
the area. Surface based CAPEs of over 1500 J/kg with 0-6 km bulk
shear increasing to 30 knots will support a strong to severe
thunderstorm threat. The current Day 2 for SPC has Southeast
Michigan in a General Thunderstorm Outlook.

A dynamic behavior and evolution of the upper level ridge is
expected this week with a pseudo rex block taking shape over the
eastern United States tonight and Wednesday before the centroid
retrogrades back to the Tennessee Valley by Saturday. Latest
indications are that ridging will hold just north of Southeast
Michigan with H5 heights of 592-596 dam. Projected 850mb
temperatures during this timeframe are expected to range between 18-
19C with high temperatures rising into the lower 90s. The
uncertainty for the week regarding heat indices is on two items. 1.
Favorable setup for inertial instability-and backdoor cold front
flipping flow northerly in the Thumb for Thursday. Current high
temperatures along the Lake Huron shoreline are in the 70s. 2.
Guidance and forecasted surface dewpoints running higher than what
has been verifying. The current gridded forecast has values
reaching/exceeding 70 degrees each of the days. The cumulative
effects of consecutive days of heat and humidity will cause stress
on vulnerable individuals and populations. The heat headlines will
remain in effect.

MARINE...

Southwest winds will maintain the hot and humid conditions into
tomorrow. A high degree of surface stability with the cooler waters
should keep wind speeds under 25 knots. The exception will be in and
near and strong thunderstorms which develop. Timing and location
will be highly uncertain, but the typical peak heating of the day
into early evening hours will be favored. A cold front is now
progged to move south Wednesday night, even faster than indicated
yesterday. This will allow for northerly winds over Lake Huron on
Thursday and Friday as seasonably strong high pressure tracks
through Ontario. Even so, airmass remains warm, which should help
limit wind speeds to around 15 knots. Thus, any wave build up with
the longer fetch is expected to remain below 4 feet. A stronger cold
front looks to be on track for the second half of the weekend
however, and wind speeds then could reach or exceed 25 knots with
waves building to around 4 feet. Small craft advisories may be
needed.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory until 8 PM EDT Friday for MIZ047-053-060-068-075-082-
     083.

     Heat Advisory until 8 PM EDT Thursday for MIZ048-049-054-055-062-
     063.

     Excessive Heat Warning until 8 PM EDT Friday for MIZ061-069-070-076.

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

$$

AVIATION.....JA
DISCUSSION...CB
MARINE.......SF


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