469
FXUS63 KDTX 140357
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Thu Jun 13 2024

.KEY MESSAGES...

- Higher than usual confidence in hot and humid conditions much of
next week. Temperatures well into the 90s Monday and beyond with
relatively high humidity will likely bring the highest heat indices
we have seen so far this year.

&&

.AVIATION...

The hybrid cold front/outflow boundary is settling through central
Lower MI at forecast issuance. The boundary focuses clusters of
showers and thunderstorms supported by the broad mid level trough
covering the upper Midwest and Great Lakes. A stray thunderstorm
lingers through the late night mainly east of the terminal corridor
across the Thumb region. The surface front/boundary then continues
moving north to south across the area with questions still raised on
the scope of any low cloud coverage. Late evening observations
support model projections that still have clouds developing overhead
rather than moving in with the boundary. Other than a short period
of MVFR ceiling, timing the wind shift may be the weather highlight
until early in the morning. Inbound high pressure and associated
northerly boundary layer wind bring low level dry air into the
region through the afternoon while another mid level wave carries in
mid to high level clouds. Any ceiling is well above 5000 ft late in
the day into Friday evening.

For DTW/D21 Convection... Isolated thunderstorms are possible toward
the northern reach of D21 but not at DTW late tonight. Dry weather
is expected late tonight through Friday evening.

 DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less late tonight and early in the
  morning.

&&

.PREV DISCUSSION...
Issued at 335 PM EDT Thu Jun 13 2024

DISCUSSION...

CAMs finally begin to converge on the severe weather potential for
today. Line of storms looks to move southeast across the CWA between
4pm and 10pm tonight. The bulk of the storms will be to the southwest
in Indiana and Illinois, but there is still potential for severe
weather in southeast Michigan. Most of the CWA is under a Slight Risk
for severe weather, with wind and hail being the primary threats. An
isolated tornado also cannot be ruled out. SBCAPE will hit 1500 J/kg
or better due to overachieving daytime temperatures, with lapse
rates pushing 7 C/km help updrafts to develop.Shear of 30- 40 knots
has the potential to sustain anything that does develop, but stronger
50 knots shear does not push in until overnight behind the line of
storms. Convergence along the front still does not look strong, and
any storms that do develop will quickly outrun the available
instability. While the ingredients are in place, there is still much
uncertainty with how the system will evolve over Michigan. Potential
exists for a storm to pop up over the entire CWA, but the best
chances for severe weather are in the southern part of the CWA near
Wayne, Washtenaw, Monroe, and Lenawee counties. Moisture availability
is greater to the southwest, but peak PWATs of 2 inches are expected
over the CWA. Storm total QPFs sit at around 0.2 inches, but any
localized showers could easily exceed that value.

Trough pushes east on Friday, allowing high pressure to take control
and keep skies clear through Friday and Saturday. More seasonable
highs reach 80 on both Friday and Saturday, with little chances for
rain. Sunday night exhibits the next chances for rain due to an
overnight warm frontal passage and an associated shortwave trough.

Significantly warmer weather remains in the forecast as an upper
level ridge builds overhead on Sunday. 500mb heights have the
potential to reach upwards of 590dam. This allows for warm, moist
air to fill in and bring dew points in the 70s to the CWA. Daytime
highs Monday-Wednesday reach 90 degrees or better, with ensemble
means disagreeing on the full extent of heating. Both shortwave
troughs embedded within the ridge and upper level trough to the west
have the potential to bring showers to the area, which would temper
the heat down a few degrees should the timing line up. The NWS Heat
Risk identifies a Major to Extreme Risk on Tuesday and Wednesday due
to apparent temperatures pushing 100 degrees during the day, high
dew points creating muggy conditions, and lack of overnight relief
as temperatures stay above 70. Forecasted temperatures are currently
set to hit 95 degrees four days in a row, which has not been
achieved since July 1-4, 2002. If full insolation is achieved on any
of these days, temperatures could push record highs, but right now
that looks unlikely. Extended guidance holds the ridge through the
rest of the week, sustaining above average temperatures.

MARINE...

A warm air mass continues to reside over the cooler waters,
producing stable over-lake conditions. This will continue to
minimize the stronger wind gusts mixing down to the surface,
relative to the over-land nearshore zones. That said, isolated wind
gusts around 25 knots will still be possible immediately along the
land-lake interface with the southwest flow in place, especially
into inner Saginaw Bay with the ideal fetch. These stronger wind
gusts will diminish after sunset.

Otherwise, redeveloping showers and thunderstorms, some strong, will
be possible this evening, focused mainly across central Lake Huron
and locations south. Northern Lake Huron will still be susceptible
to storms, some strong, through the late afternoon.  Wind gusts to
or in excess of 34 knots and small hail will be the main threats
with any strong to severe thunderstorm development. The passage of a
cold front late tonight into tomorrow morning will veer wind
direction from southwest to northwest as high pressure builds in
behind the front. This will bring lighter winds to the Great Lakes
by tomorrow morning, lasting into the end of the week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

AVIATION.....BT
DISCUSSION...BC
MARINE.......AM


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