934
FXUS63 KDTX 220408
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1208 AM EDT Sat Aug 22 2026

.KEY MESSAGES...

-There is a Marginal/Isolated risk of strong/severe thunderstorms
 this afternoon.

- Breezy and cooler conditions arrive Sunday with a lingering chance
for showers.

- Dry weather with slightly below normal temperatures start off the
week on Monday.

&&

.AVIATION...

Predominately VFR ceilings through the early morning hours as
increased moisture supports higher coverage of mid/high clouds while
winds hold out of the S to SE. There remains low potential for stray
rain showers through the early morning hours, but coverage remains
low enough to preclude mention through remainder of tonight. Better
chance resides across FNT/MBS during the mid to late morning hours.
Cold front mid-day will bring widespread coverage of showers with
scattered thunderstorms along with potential for MVFR ceilings with
the passage of the front. Winds become westerly by the afternoon and
increase up to around 10 knots then becoming northwesterly in the
evening.

D21/DTW Convection... Very limited chance for an isolated
thunderstorm remainder of tonight and low enough to leave mention
out of TAFs. Increasing coverage of convection is expected to occur
after noon with the highest probability between 18 and 23z.

.DTW THRESHOLD PROBABILITIES...

* Very low for thunderstorms tonight. Moderate after 18z today.

* Low for ceilings at or below 5000 ft this morning. Moderate in the
  afternoon.

&&

.PREV DISCUSSION...
Issued at 301 PM EDT Fri Aug 21 2026

DISCUSSION...

A couple meso scale vorticity centers apparent on the latest
radar/satellite composite which have emerged from earlier convection
across eastern Wisconsin will track across southern and central
Lower Mi late this afternoon. This added PVA with the advection of a
narrow moisture and instability axis into Se Mi will support a
chance for convection late this afternoon and evening. Ongoing deep
layer moisture and weak elevated instability advection in advance of
the longer wavelength inbound trough will sustain chances for
convection across the entire forecast area through the night. Cloud
cover and boundary layer moisture advection will lead to a milder
night in relation to last night with min temps largely in the 60s.

Amplification of the longer wavelength trough will persist through
the weekend with the main mid level positive vorticity axis forecast
to pass across Se Mi during peak daytime heating Saturday. The
resident moist axis and diurnal heating will contribute to weak
instability by early Saturday afternoon. This will support high
chances for showers/thunderstorms, especially during the afternoon.
Cloud cover and potential early day showers will limit daytime highs
to the 70s. ML CAPE values are therefore forecast to remain at or
below 1500 J/kg. This and 0-6km bulk shear values at or below 25
knots will mitigate the severe weather risk. There has been some
trends toward a little steeper mid level lapse rates Saturday, which
could lead to some higher downdraft CAPE potential warranting an
isolated risk for some stronger/severe convection. Mean total
forecast QPF values have increased slightly over the last few model
cycle, now around 4 tenths of an inch. High end totals (95th
percentile) of 1 to 1.25 inches are possible within any slow moving
convection.

The 12Z model suite has trended toward the evolution of a deeper
more closed upper low over the eastern Great Lakes Sunday into
Monday resulting from better phasing with secondary mid level PV
anomaly dropping down from northern Ontario Sat night. This will
drive a respectable thermal trough (850mb temps down to the single
digits) across Lower Mi Sunday which now looks to persist into
Monday. This will ensure seasonally cool (almost fall-like)
temperatures to finish the weekend and start the new week. Steep low
level lapse rates and moisture flux off the Great Lakes will
contribute to ample cloud cover Sunday. This secondary short
wave/positive PV anomaly is now forecast to brush across Se Mi Sun
afternoon. Despite an overall lack of deep layer moisture, this wave
may allow a brief uptick in convective cloud depth, offering at
least a chance for some afternoon showers. A progressive northern
stream wave is forecast to bring the next chance for
showers/thunderstorms mid week (Wed/Thurs time frame). Ensemble
members still show a fair amount of spread among timing and precip
chances with this system .

MARINE...

The departure of high pressure into the Continental northeast will
allow winds across the Great Lakes to back to the southwest this
afternoon with increasing rain and thunderstorm chances building in
across northern Lake Huron ahead of the next cold front. The cold
front will progress across the Great Lakes through tomorrow morning
and afternoon, expanding rain and thunderstorm chances across the
remainder of the forecasted area. Winds will continue to veer to the
northwest in the wake of the passing front, and will increase in
intensity and remain elevated through Sunday as cooler is ushered
in. Wind gusts will likely range around 25 to 30 knots through the
weekend. The switch in wind direction from the northwest will
quickly build wave heights in and around the Thumb which will likely
result in the issuance of Small Craft Advisories by Sunday morning.
High pressure builds back in Monday and Tuesday which will bring
about lighter winds.

&&

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

$$

AVIATION.....AA
DISCUSSION...SC
MARINE.......AM


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