845
FXUS63 KDTX 131935
AFDDTX

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

.KEY MESSAGES...

- Warmer than normal today with high temperatures in the mid to
upper 80s and noticeably higher humidity.

- Scattered showers and thunderstorms develop this afternoon and
evening with potential for severe weather. Damaging wind gusts to 60
mph will be the main threat between 3pm and 10pm. Southeast MI is
outlined in a Marginal to Slight Risk from SPC.

- 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.

&&

.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.

&&

.PREV DISCUSSION...
Issued at 109 PM EDT Thu Jun 13 2024

AVIATION...

Difficult convection forecast for late this afternoon into early
evening hours. The 12z DTX sounding indicated a lot of dry air below
800 MB, and thus will be counting on the steepening mid level lapse
rates/increasing cape to potentially trigger strong to severe
thunderstorms late today. At this point, will continue with the
inherited tempo group for TSRA at each taf site. Coverage and
location is still uncertain, and bulk of storms could end up closer
to the Michigan/Indiana border.

Cold front/wind shift will track through southeast Michigan tonight,
and low level convergence may be sufficient for a period of
borderline MVFR/VFR clouds. Unfortunately, the amount of showers and
thunderstorms that occur late this afternoon/this evening will be a
factor in determing this scenario. It appears the southern TAFS
stand the best chance and longest duration of low clouds, but should
clear around sunrise Friday regardless.

Light northerly flow tomorrow, with some sct-bkn mid cloud (5-10
kft) development expected with the cooler mid levels (zero at 700
MB) tracking through the Central Great Lakes.

For DTW/D21 Convection... A scattered-broken line of thunderstorms
looks to be developing/tracking through southeast Michigan late this
afternoon/early this evening. The primary window to affect DTW is
expected to arrive by 23Z and move east by around 02Z.

 DTW THRESHOLD PROBABILITIES...

* Moderate for thunderstorms impacting the terminal by around 23z
  today.

* Low for cigs aob 5000 ft this evening through tomorrow morning.


&&

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

$$

DISCUSSION...BC
MARINE.......AM
AVIATION.....SF


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.