977
FXUS63 KDTX 120018
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
818 PM EDT Thu Jul 11 2024

.KEY MESSAGES...

- Showers and storms hold west and north of the Tri-cities this
  evening. Chances for isolated showers and storms expand across
  Southeastern Michigan tomorrow.

- The next chances for storms comes Sunday and Monday evening.
Severe weather is possible with this system.

- A period of hot and humid conditions are forecasted for Sunday and
Monday.

&&

.AVIATION...

Broad and weak high pressure will maintain VFR conditions through
tonight with scattered showers and thunderstorms holding to the west
of TAF sites. Light winds will gradually settle out of the east-
southeast by tomorrow morning. Diurnal cumulus field develops again
tomorrow and a chance for scattered showers and thunderstorms
return. Models point towards the metro terminals as the favored area
for any activity that develops tomorrow, but coverage and and exact
location is too uncertain to mention in TAFs at this time.

For DTW/D21 Convection...Scattered showers and thunderstorms will be
possible around the D21 airspace tomorrow. Confidence in location,
coverage, and timing is too low to mention in TAFs at this time.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms tomorrow.

&&

.PREV DISCUSSION...
Issued at 339 PM EDT Thu Jul 11 2024

DISCUSSION...

Weak high pressure has built into the region today as the remnants
of Beryl continue to move off to the east. Light cumulus deck in
place has not deterred heating today, as overachieving temperatures
have pushed into the mid 80s this afternoon. Pop up showers are a
possibility tonight in the Tri-city area, but hi-res guidance has
trended away from bringing rain that far east and resolves
developing showers raining themselves out on the west side of the
state.

Friday shows a bit better chances for shower potential over the CWA.
Daytime heating will push temperatures into the mid-80s and allow
for SBCAPE values to reach up to 1000 J/kg. Shear up to 30 knots
will be more prevalent over the southern part of the CWA, so
expecting any popup showers or storms to have the best chances to
sustain themselves in that environment. Warm air advection at the
700-600 hPa layer is set to move in Friday evening, potentially
shutting off convection depending on how warm the profile gets.
Early timing of the warm air or underperforming surface temperatures
may also limit the convective ability of these storms. Severe
weather is not currently expected out of this setup.

Weak ridging on Saturday maintains support of high pressure and
keeps relatively clear skies and dry conditions in place.
Temperatures will increase into the upper 80s, with some urban areas
having the potential to touch 90 degrees on Saturday.

A weak warm front has to potential to develop and move in Sunday
followed by a cold front from the same low pressure system on
Monday. Moisture will build with the passage of the warm front
Sunday as PWATs between 1.5 and 2 inches will take hold and dew
points will rise into the low to mid 70s. There is some concern for
heat as a hazard for these two days, especially due to the lack of
overnight relief. Highs on Sunday are expected to reach the upper
80s to low 90s, and overnight temperatures on Sunday are not
expected to drop below 70 degrees before rebounding back up to 90
degrees on Monday. The NWS HeatRisk product gives a Moderate to
Major risk of heat-related impacts across the CWA on Monday for
those without an effective way to cool off. Urban areas in and
around Metro Detroit have the highest risk.

In terms of severe weather potential, early looks for Sunday/Monday
show CAPE values around 2000 J/kg. Directional shear will be present
for the event and creates clockwise hodographs, although shear
conditions are far from perfect. Wind speeds at the upper levels on
Sunday in particular will be outpaced by lower-level winds, creating
favorable conditions for storm development in the lower few thousand
feet of the atmosphere but providing a potential obstacle for storms
to develop further up. Another obstacle for any convection looks to
be a small temperature inversion around 800 hPa present both days.
Updrafts will likely be able to overcome this either by eroding the
cap or by using forcing from the front. Despite these obstacles,
convection is expected for these periods at this time, with Monday
looking to be the best shot at severe weather.

Conditions will dry out and cool down after frontal passage on
Tuesday as high pressure moves into the Great Lakes once again and
upper level ridge to the west remains stagnant for the foreseeable
future. Dew points will drop back down into the low 60s-upper 50s
and seasonal to below-seasonal temperatures are expected.

MARINE...

An area of weakly organized high pressure provides a diminished wind
field across the central Great Lakes this afternoon and evening,
evidenced by single digit marine anemometer readings (as of 19Z). A
weak area of convergence could drift east this evening and sustain
some isolated thunderstorms, mainly over Saginaw Bay. Otherwise,
light winds organize out of the south-southeast Friday as diffuse
surface ridging drifts toward the Eastern Lakes. Winds/waves
generally hold below criteria through Saturday and likely into next
week. Main caveat associated with the potential for marginal Small
Craft Advisory wind gusts amidst veered southwest flow over Saginaw
Bay as peak afternoon winds approach 25 knots. Chance exists for
isolated showers/storms Friday afternoon before coverage expands for
Sunday and Monday with some stronger storms. Late weekend and early
next week storms should pose a higher risk for locally higher
winds/waves and hail.

&&

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

$$

AVIATION.....AA
DISCUSSION...BC
MARINE.......KGK


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