Expert Forecast Opinion

856
FXUS63 KDTX 090350
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1150 PM EDT Wed Oct 8 2025

.KEY MESSAGES...

- Frost Advisory in effect Midnight tonight until 9am Thursday for
much of Southeast Michigan outside of the Detroit urban heat island.

- Potential for frost Friday morning as temperatures fall into the
mid to upper 30s.

- Unsettled conditions possible this weekend as low pressure moves
into the Great Lakes.

&&

.AVIATION...

High pressure will maintain control this period, ensuring VFR
conditions within a very dry environment. Light northeast flow will
draw some moisture off lake Huron into the region overnight, which
may afford some brief intervals of lower VFR, particularly near MBS.
Otherwise, limited cloud production through Thursday given the
magnitude of the ambient dry layer. Winds remain modest from an
easterly direction during the daylight period. Some degree of
moisture flux off lake Erie may lead to some expansion of lower
cloud Thursday night.

For DTW/D21 Convection...No convection will occur through the TAF
period.

DTW THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 349 PM EDT Wed Oct 8 2025

DISCUSSION...

Prototypical, cool, Autumn conditions are in place this afternoon
with polar high pressure building into the Great Lakes regions from
the northwest. Differential cold advection in the lower troposphere
has resulted in strong midlevel static stability with nothing more
than flat, low coverage diurnal cumulus. Favorable radiative cooling
conditions will develop for many locations with clear skies and calm
winds. The exception will be those areas immediately downwind of Lake
Huron. Multiple guidance sources suggest a light easterly wind
direction holding on throughout the night. This would result in a
warmer wind off of the water in addition to the advection of some
lake cloud. Based off of NBM-CONUS data and the probabilities for
temperatures of less than 37 degrees, went ahead and decided for
Frost Advisories for all counties in Southeast Michigan except Wayne
County (NBM probabilities of less than 37 is at 8% for much of the
county, 13% Northville to Plymouth). Off of a cold start, highs
Thursday are forecasted to be around 60 degrees, some 5 degrees
below average.

Consensus of operational runs, including the 08.12Z control run of
the ECMWF, directs a vigorous shortwave southeastward into the Great
Lakes Friday. The overwhelming consensus then predicts the closed
low circulation to stall out overhead as a blocking ridge rapidly
organizes off the East Coast and through Quebec. Latest European
ensemble data with EC-AIFS keeps the precipitation footprint
relatively progressive carrying light QPF amounts eastward into
Canada by midday Saturday. The latest forecast has chance PoPs
Friday evening through Saturday evening which appears reasonable.
Best proxy for precipitation chances across the area will be when
500mb temperatures crash into the -20 to -23C range. However, slower
timing and a very dry subcloud layer in advance of the system could
limit coverage. Important to note that Control run of the ECMWF is
running significantly wetter than the ensemble data. For DTW, the
interquartile range for 24 hour QPF amounts at 12Z Sunday is between
0.1 and 0.4 of an inch.

Aggressive surface ridging is forecasted to build back into
Southeast Michigan for the beginning of next week. Pleasant weather
with temperatures some 5 degree above normal.

MARINE...

High pressure drifts directly over the central Great Lakes this
evening-tonight resulting in a steady reduction in wind speeds and
subsequent waves going into Thursday. Southwesterly winds then
increase Thursday night as high pressure shifts towards the
Northeast ahead of low pressure dropping out of northern Canada.
Said low looks to slowly track over the Great Lakes this weekend
bringing renewed shower and waterspout chances however winds remain
more modest, generally between 15-25kts.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Frost Advisory until 9 AM EDT Thursday for MIZ047>049-053>055-
060>063-068>070-075-082-083.

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

$$

AVIATION.....MR
DISCUSSION...CB
MARINE.......KDK

You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.