928
FXUS63 KDTX 200752
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
352 AM EDT Wed Aug 20 2025

.KEY MESSAGES...

- Seasonable temperatures and dry weather expected today through
  Friday.

- Rain chances return this weekend as low pressure drags a cold front
  through the area.

&&

.DISCUSSION...

Overcast skies blanket much of lower Michigan this morning as low
level moisture continues to wrap into the western quadrants of the
departing surface low. Gradient flow between 5-10 knots has kept
moisture elevated to support low stratus rather than fog. The
thicker layer of synoptic moisture will gradually fade through the
morning, only to be replenished by Lake Huron moisture advection
which keeps a healthy coverage of cloud cover through most of the
daylight hours. Temperatures thus likely to stay in the mid 70s,
with a few spots in the upper 70s in the Saginaw Valley/urban
footprint.

Cloud cover wanes overnight while PW drops below 1" to highlight the
very dry airmass advecting into the region. Temperatures moderate
slightly through the rest of the work week as the subsidence
inversion gradually breaks down. High temperatures trend toward
normal, with highs in the upper 70s on Thursday and low 80s by
Friday. Dry conditions and plenty of sunshine result in a pleasant
couple days of late August weather across SE Michigan.

Next chance for rain arrives this weekend, with the parent weather
system organizing west of the Mississippi River over the next couple
of days. Strong ridging over western CONUS has led to an anomalous
thermal ridge characterized by 850mb temperatures of 25-30 C as far
north as Alberta/Saskatchewan (aoa maximum climatology per NAEFS). A
strong upper low will track eastward through the Canadian provinces
and eventually engage this warm/unstable airmass to induce
cyclogenesis in the lee of the Canadian Rockies Thursday night. The
low will then track towards James Bay this weekend and drag a cold
front across the Great Lakes in its wake. Timing of the front looks
to coincide with peak heating, but lackluster moisture convergence
ahead of the front really cuts into instability prospects and QPF.
Thunderstorm chances will be greatest over the Thumb region where
the lake influence provides a slight advantage in boundary layer
moisture.

Passage of the cold front will mark the transition to a much cooler
airmass as the James Bay low stalls through early next week. Cool
northwest flow across the seasonably warm waters of Lake
Superior/Lake Michigan will generate periods of cloud cover/shower
potential while temperatures hold in the low to mid 70s.

&&

.MARINE...

Prevailing northeast wind affects the area today as low pressure
tracks into the eastern Great Lakes. The peak in wind will be this
afternoon across the southern Lake Huron basin and Saginaw Bay where
winds will reach 15 to 20 knots with gusts up to 25 knots. A Small
Craft Advisory remains in effect for all nearshore waters from
Saginaw Bay to Port Huron as waves build into the 3 to 5 foot range.
Wind magnitude and wave heights will gradually decrease through
tonight. Lighter northeast wind persists across the region into
Thursday as high pressure builds in across the northern Great Lakes.
Wind then shifts to southwest on Friday ahead of the next cold front
set to arrive on Saturday. A period of gusty conditions looks
increasingly likely by this weekend as robust cold air advection
begins to work into the region.

&&

.PREV DISCUSSION...
Issued at 1134 PM EDT Tue Aug 19 2025

AVIATION...

Ongoing shallow cool air advection and ample low level moisture has
led to a widespread low stratus. Observational trends and recent
model guidance suggest a prevailing low end MVFR and IFR ceilings
through daybreak. The northern gradient flow will sustain winds
around 10 knots and will be a limiting factor for much if any fog.
Some brief minor visibility restriction may however be possible
within any areas of early morning drizzle. Low level dry air
advection and diurnal heating/mixing will result in a steady
improving trend in ceiling heights during the day Wednesday. Some
veering of the low level winds fields toward the north-northeast Wed
afternoon and evening may sustain a strato field across portions of
Se Mi into Wed night given the added moisture flux off the lakes.

For DTW/D21 Convection...No thunderstorms are forecast through the
TAF period.

THRESHOLD PROBABILITIES...

* High for ceilings aob 5000 feet tonight and Wednesday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 8 AM EDT this morning through this
     evening for MIZ049-055-063.

Lake Huron...Small Craft Advisory from 8 AM this morning to 10 PM EDT this
     evening for LHZ421-422-441>443.

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

$$

DISCUSSION...MV
MARINE.......TF
AVIATION.....SC


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