482
FXUS63 KDTX 221125
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
725 AM EDT Fri Aug 22 2025

.KEY MESSAGES...

- Patchy fog early this morning may become locally dense before
sunrise. Dry and seasonable weather today.

- Scattered showers and thunderstorms are possible Saturday
afternoon. Severe weather is not likely.

- Below normal temperatures Sunday through Wednesday with highs in
the upper 60s to 70s.

&&

.AVIATION...

Fog has largely stayed away from most TAF sites through much of the
morning with MBS and FNT experiencing the lowest vsby drops, though
fluctuating up and down. Any lingering fog should dissipate in the
first hour or so to start this TAF period. VFR conditions will then
prevail through the day as winds shift out of the south to southwest
this afternoon into tonight. Should see scattered VFR cumulus this
afternoon to around 4.5 kft with increasing high clouds late in the
day and tonight.

For DTW/D21 Convection... No thunderstorms expected through the TAF
period.

THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 335 AM EDT Fri Aug 22 2025

DISCUSSION...

A mid-level ridge folds over the region this morning, sustaining
continued subsidence and progression of 1019 mb surface high
pressure overhead. Calm conditions within the preconditioned moist
boundary layer and clear skies overnight led to patchy fog
development outside of the Metro area that will carry through the
early morning hours before mixing out shortly after sunrise. Some
locales may see dense fog. Pleasant late August conditions ensue
with partly cloudy skies, highs in the lower 80s, and seasonable
humidity with dew points in the lower 60s. The high pressure becomes
displaced south tonight, inducing a light southwest gradient which
keeps the marine plume offshore. There may be enough residual
surface layer moisture for some patchy, shallow ground fog Saturday
morning but do not expect as expansive of coverage as this morning.

Saturday will see the arrival of a cold front driven across the
Great Lakes by low pressure tracking across northern Ontario. This
system will be nearing occlusion with the bulk of the upper jet
forcing passing north of SE MI. Still, a narrow plume of 1000-850mb
theta-e transport preceding the front and timing during the peak in
the diurnal cycle supports potential for scattered showers and
storms during the afternoon. The Thumb carries higher PoPs (40 to
60%) as models highlight unbalanced flow at the nose of the 700mb
jet that looks to serve as locally enhanced forcing there. Bulk 0 to
6 km wind shear increasing to 35+ kt would support storm
organization and a potential severe threat, but instability looks to
be the limiting factor as the remnant mid-level stability is slow to
erode. Available ML guidance offers very low severe probability and
SPC day 2 outlook maintains a general TSTM mention.

The front marks a pattern shift with the upper low stalling over
northern Ontario through the weekend. This ushers in a thermal
trough with 850 mb temp trending down to around 4 to 6 C Monday into
Tuesday, supporting highs around 70 and lows in the 40s/50s. Several
shortwaves will pivot over the region through the early week leading
to unsettled conditions with periodic light lake effect showers
and/or drizzle. The trough shows signs of easing eastward mid-week
to allow for some moderation in the below normal temps, but ensemble
guidance maintains a broad area of negative height anomalies over
eastern North America through at least Friday.

MARINE...

Center of high pressure continues to drift over the central Great
Lakes today maintaining lighter winds that gradually reorganize out
of the southwest. A broad low pressure system tracks across northern
Ontario late tonight-Saturday which will send a cold front through
the Great Lakes on Saturday bringing the next chances for showers
and thunderstorms. An upper trough then settles over the region
through the rest of the weekend and into next week resulting in fall
like conditions across the Great Lakes. West/northwesterly winds
will gust to around 25 knots this weekend. An uptick in winds
towards 30kts looks to occur Monday as the the core of the airmass
reaches the region. Cooler weather brings lake effect shower and
waterspout chances through that timeframe.

&&

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

$$

AVIATION.....AA
DISCUSSION...TF
MARINE.......KDK


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