408
FXUS63 KDTX 081938
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
338 PM EDT Tue Jul 8 2025

.KEY MESSAGES...

- Dry and seasonable conditions through the evening. Increasing
chances for some showers and thunderstorms late tonight through
tomorrow morning.

- Shower and thunderstorm potential and coverage increases through
tomorrow afternoon and evening. The strongest storms will be capable
of producing wind gust around 45-55 mph. Highly localized flooding
remains possible.

- Dry and warmer conditions return Thursday and Friday.

&&

.DISCUSSION...

Tranquil conditions persist through the afternoon and evening with
seasonal temperatures. Elevated instability increases overnight as a
plume of theta-e rich air spreads into the region, with MUCAPE
values gradually increasing. While low-level WAA remains limited,
low-amplitude mid-level troughing pivots over the Great Lakes and
coupled with subtle convergence within the theta-e plume, will bring
increasing chances for elevated showers and thunderstorms late
tonight through tomorrow morning. By tomorrow afternoon and evening,
showers and thunderstorms will turn surface based as instability
rises aoa 1000 j/kg, fueled by diurnal heating. Some better forcing
will be found along a cold front that will pivot through the Tri-
Cities, Thumb and Flint region through the afternoon and early
evening hours. Additional weak convergence along lake boundary and
intrusion of southwest flow near the border will also be potential
areas for shower and thunderstorm development through the day.
Scattered to numerous showers with embedded storm development is
expected given the above.

Shear values are modest with 1-6km values of 20 knots, bringing the
potential for organized convection of isolated to multicellular
variety. The main threats will be stronger gust potential of 45-55
mph and small hail. Slow storm motions will bring the chance for
highly localized flooding potential. Please see the hydrology
section for additional details.  The moisture-rich low-levels will
likely be an inhibiting factor for any stronger mentions of gusts
reaching severe criteria. Instability wanes while the front clears
late tomorrow night, ending all precipitation chances.

Upper-level confluence will reinforce high pressure across the state
Thursday with its influence extending into Friday as high pressure
washes out across New England and the western Atlantic. This will
bring dry conditions through the end of the week with seasonal
temperatures. The next chance for showers and thunderstorms will
enter in the Saturday-Sunday timeframe. An upper-level disturbance
will come onshore across northern California into the Four Corners
before shearing out across the Midwest and Great Lakes. An upper-
level trough will trail the wave over the northern Plains, with this
prefrontal trough/cold front combination bringing the chance for
showers and thunderstorms. There still remains questions on phasing
of the aforementioned features, but the boost in warm air advection
ahead of any troughing feature does bring the chance for some
slightly above normal temperatures by Saturday, potentially
challenging the 90s through the Metro region.

&&

.MARINE...

Light and variable winds remain in place this afternoon and evening
as diffuse surface pressure field lingers over the central Great
Lakes a bit longer. A weak surface low/trough drifts across northern
Lower Michigan tonight and out over Lake Huron Wednesday while
gentle winds organize out of the SE. This draws more humid and
increasingly unstable air into the region while the governing upper
low tracks across eastern Ontario into western Quebec. The
combination of forcing and instability ensure periodic thunderstorms
Wednesday afternoon and evening, with later rounds tied to the
passage of the system`s cold front. Ambient dynamics are rather weak
which should keep prevailing conditions below Small Craft Advisory
criteria, but locally higher winds/waves are possible with some
stronger storms that might develop. Shortwave ridging slides east
Thursday allowing surface high pressure to build in from the Upper
Midwest which facilitates mainly dry conditions across the
waterways. A more robust low moves in late Friday into Saturday
with renewed potential for showers and storms.

&&

.HYDROLOGY...

Scattered to numerous showers and thunderstorms are forecast
tomorrow. Storms will be relatively disorganized, but with humid
conditions and slow storm movement, storms will be capable of
producing torrential downpours. Localized areas may receive over 1
inch per hour, with extremely localized rainfall totals ranging from
1-3+ inches, pending any thunderstorms training or repeated
thunderstorm activity. Highly localized flooding of urban areas,
small streams, and otherwise poorly drained areas will be possible.
The main threat for flooding will be between 1pm and 9pm.

&&

.PREV DISCUSSION...
Issued at 209 PM EDT Tue Jul 8 2025

AVIATION...

High pressure currently over the area will keep winds light with
some sct diurnal cu around today. Winds will emerge out of the
west/southwest ahead of a weak trough approaching this evening. Warm
front lifting through this evening tied to a weak low may spark a
few widely scattered showers after dark with the best chance of
affecting MBS. Better chance of showers and possible thunderstorms
comes tonight after midnight when the first mid level system lifts
through SE MI. Trailing front could stall across the area keeping
showers going after 12Z from FNT southward. Will leave out of the
TAFs right now in favor of noting the frontal passage later in the
afternoon which could bring another round of storms after 18Z.

For DTW/D21 Convection... No convection through the daylight hours
today. Low confidence on timing and occurrence of showers/storms in
the vicinity mainly after 06z Wednesday. Convection could remain in
the vicinity through the morning but better chance of renewed
activity will be after 20Z.

THRESHOLD PROBABILITIES...

* Low for thunderstorms after midnight into Wednesday morning, and
  again Wednesday later afternoon.


&&

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

$$

DISCUSSION...AM
MARINE.......KGK
HYDROLOGY....AM
AVIATION.....DRK


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