Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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039
FXUS63 KDTX 132220
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
620 PM EDT Mon Oct 13 2025

.KEY MESSAGES...

- A dry cold front moves through the area Tuesday leading to cooler
temperatures Wednesday.

- There is also an increasing probability of rain Wednesday morning,
currently at about 30 percent.

- Dry weather and normal mid October temperatures resume during the
late week.

&&

.AVIATION...

A cold front on pace to sag across the region tonight. Moisture
remains limited with this frontal passage, leaving simply some
pockets of higher based VFR cloud at times. Assuming a greater
window of open sky exists within a weakening gradient, this will
again bring potential for some areas of fog and/or very low stratus
during the pre-dawn hours. Less favorable conditions than recent
nights as low level flow no longer carries an added boost off the
lakes, so confidence in occurrence at any one location remains quite
low. Forecast will continue to highlight a window between 09z and
13z for some reduction of visibility. Rapid improvement in
visibility thereafter, leaving a standard expansion of VFR diurnal
cu for Tuesday afternoon.

For DTW/D21 Convection...No thunderstorms through the taf period.

DTW THRESHOLD PROBABILITIES...

*  Low for visibilities aob 1/2 sm or ceilings aob 200 ft early
   Tuesday morning.

*  Low for cigs at or below 5000 ft Tuesday.

&&

.PREV DISCUSSION...
Issued at 334 PM EDT Mon Oct 13 2025

DISCUSSION...

Healthy diurnal cumulus field observed via visible satellite this
afternoon. Localized clear pockets reflect where widespread fog/low
stratus lingered this morning and disrupted the mixing process.
These areas are running a few degrees cooler than surrounding obs,
but still result in a pleasant fall evening with temperatures in the
upper 60s-low 70s.

Satellite also shows a continuous cloud band from northern Ontario
to Texas, marking the frontal zone that extends from the occluded
Hudson Bay low. This front has made little eastward progress today,
but will eventually get redirected equatorward across Lower Michigan
tonight/Tuesday as a surface high expands across the northern tier
states. Radar returns have decreased throughout the day with the
influx of a dry slot aloft and bifurcation of low level moisture
transport. This is on par with model trends, which support a dry
fropa Tuesday. Remnant cloud cover is expected to accompany the
frontal passage, but should be transient/shallow enough to allow for
some patchy fog development Tuesday morning. Cold advection will not
peak until Wednesday, but still expect to see a thermal gradient
from the Saginaw Valley (highs in the upper 60s) to the Ohio border
(highs in the mid 70s).

Conditions will be strongly influenced by the evolution of the upper
level ridge as the week wears on. The ridge will transition from its
current broad/flattened state into an amplified trough-ridge pair by
the end of the work week as northern stream waves carve into New
England. Locally, this results in mid-level height falls and a
southern shift to the jet stream that directs weak forcing across
the Great Lakes Wednesday morning. Moisture struggles to stay in
tact as it encounters the much drier surface high over the Great
Lakes. This high effectively stalls theta-e advection well west of
the state to limit QPF locally to a few hundredths of an inch
Wednesday morning. The thermal gradient follows a similar pivoting
pattern, with SE MI in the path of the thermal trough. Temperatures
on Wednesday only make it into the low 60s as a result.

Dry weather follows to close out the work week, followed by an
unsettled pattern this weekend as the upstream theta-e ridge
releases eastward in tandem with strong low pressure. Majority of
ensemble members generate measurable 24-hour QPF amounts Friday-this
weekend with a general warming trend anticipated.

MARINE...

Mostly dry cold front tracking through the Central Great Lakes this
evening. Northwest winds will gradually increase tonight and Tuesday
behind the front as colder air slowly filters into the region. The
coldest air will arrive early Wednesday morning, as 850 MB temps
drop into the low to mid single numbers. Winds will be out of the
northeast at this time as large high pressure builds through the
northern Great Lakes. With northerly sustained winds around 20 knots
Tuesday night, the prolonged long fetch will likely be enough to
build waves at or above 4 feet over the southern Lake Huron Basin.
Winds to then become light and variable to end the work week as the
high pressure system becomes fully entrenched.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 5 PM Tuesday to 5 PM EDT Wednesday for
     LHZ421-441>443.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....MR
DISCUSSION...MV
MARINE.......SF


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