389
FXUS63 KDTX 191932
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
332 PM EDT Sun Jul 19 2026

.KEY MESSAGES...

- A statewide Air Quality Alert is in effect through Monday as
  additional wildfire smoke filters across Michigan.

- The next round of showers and thunderstorms arrives Monday night
  into Tuesday that poses a Marginal Risk for severe weather.

&&

.DISCUSSION...

Stretch of dry and stable conditions to finish the weekend period
maintained by existing high pressure. High remains anchored locally
through tonight, affording a window of meaningful radiational
cooling as a weak pressure gradient and clear sky capitalizes on a
slight reduction in moisture quality. This will yield overnight lows
in the mid-50s across some rural zones and lower 60s within the
Detroit urban heat island. Air quality will remain a concern into
tonight as the Canadian wildfire smoke plume trapped beneath the
strengthening near-surface subsidence inversion continues to
oscillate across the lower peninsula. HRRR-Smoke profiles suggest
localized visibility restrictions in haze/smoke through early Monday
morning.

Dry and seasonable conditions exist into Monday. High pressure slips
off to the Mid-Atlantic coast, affording a modest window of low
level warm air advection as flow emerges from the south. This will
support highs generally in the lower 80s. Potential does exist for a
remnant convectively induced/enhanced vort max to eject out of the
upper midwest and track into the lower peninsula late afternoon/
evening. Little evidence to suggest anything more than some increase
in high based cloud should this scenario materialize, given the lack
of both greater moisture quality or instability at this stage.

Attention then turns to the implications of greater height falls
expected to expand across the great lakes Monday night and Tuesday.
Convective initiation and expansion likely west of lake Mi by Mon
evening as increasing large scale ascent supplements ongoing deeper
moisture transport within the greatest instability reservoir. While
some degree of nocturnal moisture advection will occur given the
magnitude and trajectory of 850 mb flow, there remains some question
as to depth and scale of this process. This subsequently casts
greater uncertainty as to prospective convective coverage and vigor
as ongoing activity spills downstream and into an inherently less
receptive early morning window /after 06z/. Forecast continues to
highlight a high likelihood of showers with embedded thunderstorms,
carrying an isolated risk for strong wind gusts should a more
supportive low level environment manifest despite the overnight
timing. The parent shortwave and trailing cold front will move
across Lower Michigan during the day Tuesday. Substantial cloud
cover and ongoing morning shower activity will hamper
destabilization, but trailing forcing along the cold front will keep
a chance of scattered showers and thunderstorms in the forecast
through Tuesday afternoon.

A deep upper-level closed low establishes over northern Ontario
Wednesday, maintaining broad cyclonic flow over the Great Lakes. A
solid period of cold advection by July standards will drop 850 mb
temperatures into the single digits by afternoon. A steep lapse rate
environment should offer a generous stratocu field, while lending to
a lower end potential for diurnal shower production mainly across
the thumb. Highs firmly below average in the low to mid 70s. The
region remains tucked within the eastern edge of the dominant
western US ridge, keeping dry but cooler northwest flow in place to
finish the work week. Surface high pressure builds back over the
Ohio Valley, suppressing convective chances and offering high
insolation potential. Temperature remain at or just below average
this period.

&&

.MARINE...

High pressure commands control of the central Great Lakes today
supporting dry conditions and prevailing winds below headline
criteria. Unsettled conditions build in late Monday and Monday
night, as a strong low pressure system tracks across
central/southern Ontario. Gusty winds ahead of the attendant front
may lead to a period of Small Craft Advisory conditions,
particularly across Saginaw Bay, where southwesterly flow could
channel more efficiently. A Small Craft Advisory will likely be
issued with the evening forecast update. Potential for showers and
thunderstorms then increases across the waterways as the front moves
through supporting periods of locally higher winds and waves. Wet
weather could persist into Tuesday before high pressure from
Alberta/Manitoba builds in by Tuesday evening with a drying effect.
Strong gradient flow arises Tuesday afternoon with an energetic
northwesterly low-level jet favoring low-end potential for gales
across the Huron basin. Favorable dynamics remain in-place through
Wednesday.

&&

.PREV DISCUSSION...
Issued at 128 PM EDT Sun Jul 19 2026

AVIATION...

High pressure remains west of the airspace, maintaining light
northerly flow direction at all terminals. A localized shift to the
E (possibly SE) flow is expected this afternoon at DET/DTW/YIP with
a lake breeze off of Lake Erie and Lake St. Clair, although wind
speeds remain light aob 10 knots. Hazy conditions are the result of
wildfire smoke from Canada, which will continue through tonight
until winds fully flip to the south Monday as the high drifts into
Ontario. MVFR restrictions thus continue. Otherwise, healthy
coverage of diurnal cumulus keeps low VFR ceilings around until
sunset.

D21/DTW Convection...No thunderstorms are forecast through the next
30 hours.

DTW THRESHOLD PROBABILITIES...

* Medium in ceilings aob 5000 feet through the afternoon, low
  tonight and Monday.


&&

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

$$

DISCUSSION...MR
MARINE.......KGK
AVIATION.....MV

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at www.weather.gov/detroit.