Expert Forecast Opinion

876
FXUS63 KDTX 101958
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
358 PM EDT Sun Aug 10 2025

.KEY MESSAGES...

- Warm and muggy conditions continue today through Tuesday with highs
in the low 90s and heating indices in the mid-90s.

- Dry conditions this evening with increasing thunderstorm chances
Monday and Tuesday.

- Heavy rainfall is possible this week, especially Tuesday and
Tuesday night.

&&

.DISCUSSION...

Warm and muggy conditions are felt across the entire state today
with observed heat indices in the mid 90s at press time. Much drier
conditions are found aloft with dewpoint depressions rapidly
dropping toward 15-20 C above 850mb in the 12z KDTX sounding. This
has and will continue to establish a capping inversion for most of
the forecast area, with the exception of the northern Saginaw Valley
where isolated convection has started percolating in a slightly less
capped environment.

Very gradual and weak period of height falls emerges on Monday as
low pressure dives into the Dakotas. This weakens/shifts the ridge
axis just enough to the east to direct moisture transport into Lower
Michigan. Increasing cirrus coverage will be the first indication of
this pattern shift, representing the increasing column moisture that
erodes the capping inversion late in the day. Expecting warm
temperatures again on Monday, but the introduction of cloud cover
and convective influence later in the day keeps highs a couple of
degrees cooler than today. Still, will be a warm and muggy day
across the entire CWA as heat indices again rise into the low to mid
90s. Increasing thunderstorm chances exist through the afternoon-
evening as a secondary weak low lifts from WI to eastern Ontario
tonight-Monday. This draws a subtle surface trough through lower
Michigan during peak heating, which will be the trigger for storm
potential. A few thermodynamically driven gusts of 40+ mph and heavy
rainfall due to slow-moving storms (<25 mph) will be the main
threats on Monday, but absence of mid-level flow (30 knots or less)
keeps storm mode disorganized and multicellular.

Attention turns to the Monday night-Tuesday morning period in which
moisture transport holds firmly in place and low level jet forcing
increases atop an elevated instability gradient. There are limited
hi-res runs for this period, but those that do exist show convection
developing on the nose of the LLJ. Moisture is plentiful as PWAT
approaches 2 inches and nocturnal timing of the feature all warrant
watching for heavy rainfall potential early Tuesday morning, on the
condition that rain even develops.

A challenging forecast is then in store For Tuesday/Tuesday night
until the synoptic front and upper level trough slide through
overnight. The moisture-rich airmass will stick around and keep
warm/muggy conditions in place for a third day, with heat indices
again in the low to mid 90s. These moist boundary layer conditions
are well-primed for early surface destabilization, eroding the low
level cap late morning-early afternoon (pending any convective
contamination). Forcing during the daylight hours looks to be
relatively weak and/or convectively generated, and while certainly
capable of generating convection in this type of environment,
affords low predictability at this point in the forecast cycle. The
more focused forcing comes with the arrival of the cold front
Tuesday night, which lags behind peak heating but does offer the
best organized thunderstorm potential in addition to heavy rainfall
potential.

As the cold front tracks through late Tuesday-early Wednesday
morning, a cooler airmass floods into the region and brings daytime
highs into the mid 80s for the back half of the work week. High
pressure also fills in to support drier weather Wednesday through
Friday.

&&

.MARINE...

Favorable marine conditions for most of the central Great Lakes
today as the periphery of high pressure maintains some component of
stability. Main concern for any thunderstorm activity will focus
over northern Lake Huron. Southwest flow will be gusty at times, but
should generally stay below 25 knots. Southwesterly winds persist
into Monday and Tuesday with a similar corridor of concern for
additional convective activity. Slight forward progress of an
inbound cold front may suffice in expanding the area of storms into
central Lake Huron, perhaps even beyond Saginaw Bay. The front will
take until midweek to clear through the region which maintains
chances for showers/thunderstorms across all waterways. The front
exits Tuesday night, followed by a zonal wind shift into Wednesday.

&&

.HYDROLOGY...

Multiple rounds of showers and thunderstorms are possible Monday and
Tuesday ahead of a cold front that tracks through the area Tuesday
night. Moisture rich conditions are characterized by PWAT values up
to 2 inches and dewpoints in the low 70s. Scattered thunderstorm
activity will be capable of producing heavy rainfall with rates over
an inch per hour Monday afternoon and evening. This will be followed
by multiple potential waves of thunderstorms Tuesday through
Wednesday morning, in which slow-moving and/or training
thunderstorms will be possible. There is a signal in some model
guidance for total rainfall amounts of several inches to occur by
Wednesday morning, but confidence is low at this time. Flash
flooding will be possible in urban and low-lying areas along with
rises in areas rivers.

&&

Elevated frontal slope lingers over the southern half of SE MI this
morning. Overall radar trends have shown lighter, more disorganized
showers trending potential rainfall totals lower. Still can`t
completely rule out some heavier showers along or south of the I-94
corridor this morning that could lead to narrow enhanced totals near
an inch. On average however, these southern areas expected to see
rainfall totals closer to 0.5-0.75" by the end of the morning.
Lesser amounts, likely below 0.25", for areas north. Aside from
areas that saw heavy rain/flooding yesterday evening that would be
more susceptible, this additional rain expected to only support
minor flooding in flood-prone/low lying areas.
.PREV DISCUSSION...
Issued at 1246 PM EDT Sun Aug 10 2025

AVIATION...

The 12Z DTX sounding and latest ACARS soundings around Se Mi
indicate weak mid level capping overhead. Some drop in sfc dewpoints
is forecast with continued diurnal mixing this afternoon, limiting
ML CAPE/instability. This will result in a limiting factor for late
afternoon convective development in light of the lack of forcing and
mid level capping. South winds in the 10 to 20 knot range and the
afternoon cu field will decrease during the evening with the loss in
daytime heating.

For DTW/D21 Convection... Thunderstorms are not expected today and
tonight.

THRESHOLD PROBABILITIES...

* None.


&&

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

$$

DISCUSSION...MV
MARINE.......KGK
HYDROLOGY....MV
AVIATION.....SC


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