940
FXUS63 KDTX 091100
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
700 AM EDT Wed Jul 9 2025

.KEY MESSAGES...

- Morning showers and storms are likely to remain sub-severe, but
will be capable of producing heavy downpours and localized ponding.

- Numerous showers and thunderstorms are likely this afternoon and
evening. The strongest storms will be capable of producing isolated
wind gusts around 50 to 60 mph and small hail. Isolated flooding
is also possible through this evening.

- Dry conditions are favored Thursday and Friday with a warm-up
expected Friday into Saturday.

- The next chance of thunderstorms arrives Saturday, with some
strong storms possible.

&&

.AVIATION...

Corridor of elevated convection accompanying a warm frontal boundary
will continue to lift through the region this morning. Showers
likely with some reduction of cloud base/visibility into MVFR
plausible within the heaviest downpours, with PTK and FNT most
susceptible based on latest radar trends. Embedded thunderstorms
remain a possibility with this early day activity. Focus then turns
to the afternoon and evening period, as increasingly humid
environment prompts greater destabilization with time. This will
lead to a scattered to possibly numerous coverage of showers and
thunderstorms between mid afternoon and the evening hours.  The
environment is favorable for clusters of storms with water loaded
updrafts capable of producing stronger outflow winds and heavy rain.
Rapid decline in convective potential as stability improves after 00-
01z. Pre-frontal environment maintains a modest southwest
trajectory, before a southward sagging front brings a wind shift to
light northerly tonight. A weak signal for a brief period of stratus
and/or shallow fog within the immediate wake of the frontal passage
late tonight remains worthy monitoring.

For DTW/D21 Convection...Lower probability for a thunderstorm will
persist this morning. Greater potential during the afternoon and
evening hours. Gusty thunderstorm outflow winds will be possible
with any stronger, more organized clusters of storms.

THRESHOLD PROBABILITIES...

* Low for thunderstorms this morning, then medium this afternoon and
  evening.

* Low for cigs aob 5000 ft this afternoon through tonight.

&&

.PREV DISCUSSION...
Issued at 353 AM EDT Wed Jul 9 2025

DISCUSSION...

A moist environment within a sfc-850mb theta-e tongue has supported
blossoming elevated convection overnight with radar derived rainfall
estimates so far reaching 0.75 to 1.25" in the heaviest slow-moving
storms. These have been driven along the nose of a weak LLJ beneath
ascent tied to upper jet entrance region. The LLJ weakens and upper
jet forcing eases east through the mid morning hours which should
bring a relative lull in precip coverage mid to late morning. The
plume of instability holds in place through the day to continue to
support convective chances, gradually becoming surface based with
1000 to 2000 J/kg SBCAPE this afternoon. A weak cold front working
into the area should be sufficient to trigger numerous showers and
storms this afternoon and evening. Weak flow through the column
limits deep layer wind shear to around 20 kt which keeps storms
disorganized into a pulse or multicell mode.

The probability for severe weather is low in this setup but precip
loaded downbursts will be a threat, capable of isolated wind gusts
of 40 to 60 mph. Small hail is also possible in the strongest
updrafts. Compared to recent similar setups, PWAT will be slightly
lower at around 1.50" but still supportive of localized heavy
downpours - especially given slow storm motion around 15 to 25 mph.
SE MI is highlighted in a Marginal Risk for severe weather and
excessive rainfall today with the greatest threat expected between
2pm and 10pm. Highs in the lower to mid 80s with dew point near 70F
maintains a muggy feel through the day.

Confluent northwest mid to upper flow follows passage of the trough
axis, allowing the cold front to gradually settle south of the area
on Thursday. Post-frontal thermal advection will be relatively weak,
just a degree or two drop in 850mb temp, but dew point will settle
into a slightly more comfortable range in the mid 60s. Can`t rule
out a stray lake boundary triggered shower in the far southeast
where some weak instability lingers into tomorrow afternoon, but the
subsidence in place and strong dry advection at 700mb should support
overall dry conditions and clearing skies.

Relatively high forecast uncertainty exists for the Friday period as
a ridge attempts to amplify overhead but contends with one or more
embedded shortwaves working beneath it. The bulk of shortwave energy
arriving initially will be generated by convection over the Northern
Plains tonight - the strength and timing of this activity will
influence moisture return and the cloud/precipitation forecast
Friday. There is a camp of solutions, dominated by the Canadian
ensemble, that produce a stronger trough over the Canadian Prairie
and Great Plains that appears to propel this shortwave activity in
to offer a higher chance for precip. For now, given the governing
ridge setting up and dominant signal for lower precip chances among
ensemble solutions, no reason to deviate from the NBM forecast that
carries just a slight chance of showers and storms.

Stronger signal exists for a low pressure system to track through
the region on Saturday in response to the aforementioned Plains
trough taking on a negative tilt as it pivots over the upper Great
Lakes. This period bears watching for stronger storms given higher
wind shear and potential for organized forced ascent along the
height fall center. Assuming the warm sector passes overhead during
daylight hours, highs in the upper 80s and lower 90s are achievable.
Chances for additional showers and storms carry into the weekend as
low amplitude prevailing flow offers opportunity for several
disturbances to pass over the region.

MARINE...

A weak surface low/trough drifts over Lake Huron this morning 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
this 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 today,
mainly during the afternoon and evening. Storms will be relatively
disorganized, but with humid conditions and slow storm movement east
at around 15 to 25 mph, storms will be capable of producing
torrential downpours. Localized areas may receive near 1 inch per
hour rainfall rates, with isolated rainfall totals ranging from 1 to
3 inches possible. The higher totals will be most likely for any
areas that see training or repeated thunderstorm activity. Isolated
instances of flooding of urban areas, small streams, and otherwise
poorly drained areas will be possible, especially if storms track
over locations that already received heavy rain early this morning.
The main threat for flooding will be between 2pm and 10pm.

&&

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

$$

AVIATION.....MR
DISCUSSION...TF
MARINE.......KGK
HYDROLOGY....TF


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