Expert Forecast Opinion

361
FXUS63 KDTX 091750
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
150 PM EDT Thu Oct 9 2025

.KEY MESSAGES...

- A Frost Advisory is in effect from midnight until 9 AM Friday
morning.

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

&&

.AVIATION...

High pressure centered near Toronto maintains favorable aviation
conditions for the terminal airspace through the rest of today with
ENE winds AOB 10 knots. Diurnal/lake-augmented VFR cloud field
dissipates this evening with a period of SKC likely. Some signal
exists for borderline MVFR stratus off Lake Erie early Friday which
may affect the Metro terminals. However, modeled saturation lends
some uncertainty in the generation of BKN-OVC skies. Otherwise, low
cloud fraction emerges through the first half of Friday with light
winds organizing out of the SSW with generally light speeds.

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

DTW THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 352 AM EDT Thu Oct 9 2025

DISCUSSION...

A chilly start to the day across southern Lower Michigan, with most
locations reporting temperatures in the mid 30s under clear skies
and light northeast winds. A Frost Advisory remains in effect
through 9am as a result. Localized warmer temperatures are observed
downwind of Saginaw Bay where stratus has moved inland and disrupted
the radiative cooling process.

Remainder of the day will feel very similar to yesterday with high
temperatures just barely reaching 60 degrees under plenty of early
October sunshine and thermal troughing. The 00z KDTX RAOB sampled
850mb temperatures right at 0 C, marking a ~15 C drop in h8
temperature over the past 48 hours. Main difference between today
and yesterday is the departure of the surface high, which
contributes to veering wind profiles toward the east-southeast. Not
expecting lake cloud to push as far inland today given the shifting
winds/shorter fetch, but there is potential for Lake Erie moisture
to get drawn into the Detroit Metro region tonight. Any cloud cover
will again inhibit radiative cooling, but cloud-free areas see lows
in the mid 30s making Friday morning another candidate for frost
headlines.

Low amplitude ridging holds in place for the majority of today, but
quickly breaks down overnight as a northern stream PV anomaly cuts
off and dives equatorward toward the Great Lakes Friday. Mid-level
heights fall in response with a shift to southwest flow in the low
levels to kickstart warm advection. This brings daytime highs into
the mid-upper 60s and increasing clouds ahead of a cold front that
dives across the area Friday evening. The fropa will struggle to
generate much QPF given shallow moisture depths, modest forcing, and
a very dry sub-cloud layer.

A much stronger synoptic response arrives overnight Friday as the
compact vort max moves into the Great Lakes. Models still exhibit
large variance in the track of the upper low, ranging anywhere from
Lake Michigan to Ontario. Most solutions support measurable QPF
across SE Michigan, but rainfall amounts will be closely tied to our
position wrt the low. The less likely scenario is one that favors a
western track (i.e. 00z NAM) where SE Michigan is upstream of the
circulation in a region of strengthening moist isentropic ascent as
the low occludes. This is represented in a handful of
models/ensemble members, and would be the most impactful as it
generates a QPF bullseye over SE Michigan. The more likely solution
brings the low track either over Lower MI or Lake Huron, pushing the
QPF bullseye into Ontario and supporting more of a convective/showery
rain event than a broad stratiform rain. Lean moisture depth
initially will be supplemented as moisture gets drawn in from a
coastal Atlantic low. Wherever the low ends up, this moisture wraps
along the isentropic slope which contributes to the aforementioned
higher QPF potential. Otherwise, expecting a standard influence of
clouds/precipitation on temperature prospects for this weekend, with
the outgoing NBM forecast in line with ensemble means.

MARINE...

The central Great Lakes remain under the influence of high pressure
now centered over southern Ontario maintaining light easterly
turning southerly winds. Winds continue to veer to the southwest by
tonight as the high departs for the Northeast ahead of low pressure
dropping out northern Canada. Once the shift to SW flow occurs,
winds undergo steady strengthening into Friday with gusts over
northern Lake Huron peaking between 20-25kts (10-20kt gusts over the
rest of the region). Aforementioned low is expected to become a
closed low as it crosses the Great Lakes resulting in slow
progression across the area through the weekend however this should
also winds under 30kts, instead generally peaking between 15-25kts.
Periodic showers accompany this low as will waterspout chances as
the cooler airmass is reinforced.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Frost Advisory from midnight tonight to 9 AM EDT Friday for
MIZ047>049-053>055-060>063-068>070-075-082.

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

$$

AVIATION.....KGK
DISCUSSION...MV
MARINE.......KDK


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