300
FXUS63 KDTX 080724
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
324 AM EDT Wed Oct 8 2025

.KEY MESSAGES...

- Cool and dry conditions persist through the rest of the week.

- Potential for frost exists Thursday and Friday mornings as
  temperatures fall into the mid to upper 30s.

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

&&

.DISCUSSION...

Broad area of 1028mb surface high pressure is analyzed across north-
central CONUS this morning, with SE Michigan residing on its eastern
flank. Most notable forecast element today is the airmass change,
with cold advection ongoing at issuance. 850mb temperatures drop
near/below 0 C within the base of the thermal trough, barely
boosting daytime highs to 60 degrees even under maximum solar
insolation.  This will be the first day since early September with
forecast temperatures falling below normal for all three climate
sites. Diurnal cloud cover will rely on Lake Huron moisture flux in
an otherwise very dry airmass (PWAT values in the 5th percentile per
daily climo). Should have no problem activating Lake Huron however
with the large delta T and northerly flow to support healthy
coverage of afternoon cloud downwind of the lake.

The cooler airmass also poses concern for frost development both
Thursday and Friday mornings. NBM min temps and majority of LREF
members are forecast to fall into the mid to upper 30s, well within
advisory thresholds. There is a signal for lake cloud to be
redirected inland as the high pressure center drifts into Ontario
late tonight, which could disrupt radiational cooling for the
lakeshore counties. Thus coolest temperatures are expected furthest
inland with less certainty in frost development near the lakeshore.

Similar conditions expected on Thursday with daytime highs right
around 60 degrees, although the high pressure center will have
shifted into eastern Ontario by this point. Easterly flow
trajectories across Lake Erie will be the main source of any diurnal
cloud. Outside of the local area, will be paying close attention to
the upper level pattern Thursday as a PV anomaly moves across
central Canada. Models begin to diverge as the wave moves into
Ontario Thursday afternoon, with many solutions breaking off the PV
anomaly and sending it equatorward toward Lower Michigan late Friday
into the weekend (08.00z GFS/NAM/ECMWF). Others keep the PV anomaly
in tact and shear it eastward with the mean flow (07.18z ECMWF),
keeping it north of the Great Lakes. The variability is noted in
ensemble QPF probabilities, with about 40-50% of members generating
measurable rainfall (at least 0.01") through the weekend. If the
upper low does in fact drop into Lower Michigan, conditions will be
unsettled with potential for rain/clouds and cooler temperatures.
The alternative scenario affords a drier weekend. Substantial
increase in PoPs in the latest NBM dataset reflect a trend in 00z
guidance toward the wetter solution.

&&

.MARINE...

Continued cold advection sustains northerly wind between 10 and 20
kt across the central Great Lakes through the day. The long fetch
down Lake Huron will bring gusts to 25 kt and high waves over 5 feet
across the southern basin. A Small Craft Advisory remains in effect
for the nearshore waters through late this evening. High pressure
then builds directly into the area tonight and offers lighter winds
and waves through Thursday. This high departs by Friday, opening the
door for modest southwest wind ahead of the next cold front arriving
into the western Great Lakes. This front will track through the
region this weekend.

&&

.PREV DISCUSSION...
Issued at 1157 PM EDT Tue Oct 7 2025

AVIATION...

A cooler and drier environment will expand across the region
overnight within a post-frontal northwest gradient. VFR conditions
prevail with simply some pockets of mid level cloud for the early
morning period. High pressure anchored to the north will maintain
control Wednesday and Wednesday night. Modest moisture flux off lake
Huron in ongoing northerly flow will attempt to counter the existing
dry airmass, affording a scattered to perhaps briefly broken
coverage of VFR diurnal cu during the afternoon. Northerly winds
peaking near 10 knots Wednesday.

For DTW/D21 Convection...Thunderstorms are not expected through the
forecast period.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less Wednesday afternoon.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-
     441>443.

     Small Craft Advisory until 10 AM EDT this morning for LHZ422.

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

$$

DISCUSSION...MV
MARINE.......TF
AVIATION.....MR


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