Chesaning, Michigan Weather Forecast Discussion

368
FXUS63 KDTX 221733
AFDDTX
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
133 PM EDT Mon Sep 22 2025
.KEY MESSAGES...
- Scattered showers and thunderstorms will be possible through the
middle of the week. Localized heavy rainfall may be possible.
- Temperatures in the 70s throughout the week which will generally
be at to slightly above normal.
&&
.AVIATION...
A good deal of low level moisture around, as indicated by surface
dew pts well into the 60s across Lower Michigan. This is making for
some chaotic cloud bases, with the northern tafs more embedded in
borderline IFR/MVFR low clouds. Will have chance of renewed
shower/thunderstorm activity late this afternoon over northern tafs,
as thunderstorm complex moving through Lake Michigan will have to be
watched.
Southern tafs are relatively stable, so not expecting
thunderstorms, but still could see some renewed light shower
activity. Winds remain very light through the taf period. As such,
with the amount of surface moisture around, dense fog is a concern
tonight. Good deal of uncertainly with amount of low clouds
around/persisting, with would lessen visibility impacts, and have
gone with a more optimistic IFR/borderline MVFR fog forecast (for
now). Fog gradually burns off tomorrow morning giving way to an
increasing chance of showers/isolated thunderstorm from northwest to
southeast during the day.
For DTW/D21 Convection...
DTW THRESHOLD PROBABILITIES...
* Low for ceilings at or below 5,000 feet, becoming medium late
  tonight.
* Low for cigs/vsby to fall to 200ft and/or 1/2sm late tonight.
* Low for thunderstorms to impact DTW tomorrow afternoon.
&&
.PREV DISCUSSION...
Issued at 318 AM EDT Mon Sep 22 2025
DISCUSSION...
Two boundaries are over the region this morning; the first a mid-
upper level baroclinic zone from Missouri to the Straits, the second
is a very poorly organized, ragged 950-750mb thetae warm front from
Flint down to the Ohio border. Very subtle features and processes at
play this morning. Currently looking at a wave of warm advection,
caused by weaker than expected upper level jet dynamics, that is
generally resulting in south to north movement of shower and
scattered thunderstorm activity. Models have suggested this activity
will continue to migrate northward through the area through
approximately 10Z this morning. System relative progs then show an
embedded low level cyclonic circulation, or two, riding along this
poorly organized near surface boundary. These circulations will help
to facilitate lift with additional shower and thunderstorm activity
late this morning and afternoon. Difficult to pin down the exact
areas impacted later on with the upper level boundary up north
across the Straits. Elevated convective activity will be possible
over all of the cwa. Lack of midlevel lapse rates again limits the
environment today. HREF data and some raw hires output suggests
MLCAPES of up to 1000 J/kg will be possible north of I 69 up to
Saginaw Bay, with less than 750 J/kg to the south over Metro
Detroit. Latest Swody1 has a Marginal designation over an extreme
eastern sliver of the forecast area near Lake St Clair down to the
Lake Erie shoreline. There is some minor hires signal that suggests
fresh diurnal convective towers could develop along the eastern cwa
border/Rivers around 18-20z. With 0-6km bulk shear magnitudes of 30
to 35 knots projected it is plausible that an isolated wind gust of
up to 50 mph could occur.
The weak lower tropospheric baroclinic zone is forecasted to remain
disorganized and relatively stationary over Southeast Michigan to
begin the period Tuesday. The boundary should begin to settle
southward over the course of the day as mean gradient flow become
increasingly easterly here in response to a deep upper level closed
low over the U.P. and Lake Superior. Despite this easterly flow, not
really seeing much low, differential cold advection happening. What
may result is a fairly moist near surface environmental profile that
could result in daytime instability. 0-6km bulk shear on Tuesday is
notably less at around 25 knots. Given the instability will continue
mention showers and thunderstorms although confidence is low
regarding timing of synoptic scale lift. The latest Swody2 just
Southeast Michigan in a General Thunder designation.
The upper level closed low circulation over the western Great Lakes
brings a period of uncertainty and potentially unsettled weather
Wednesday and Thursday. Adding to the uncertainty is the persistent
control runs of the ECMWF that want to phase a MCS system into the
synoptic upper level low system. The ECMWF wants to track a
relatively good amount of QPF into Southeast Michigan. A lot of
spread exists in the EPS data. Will monitor model trends before
offering too much specificity. The current forecast has PoPs of 50-
60%.
Fast westerly flow brings lower confidence for Friday into next
Sunday timeframe. Still will likely see a surface ridge build in for
a time but latest runs suggest a dynamic/strong trough structure
blasting through Michigan late Saturday.
MARINE...
An upper trough moves into the Great Lakes today then stalls
overhead Tuesday into Wednesday. At the surface, a warm front will
stall near the Straits today before sinking south as a cold front on
Tuesday. This maintains an unsettled pattern today into tomorrow
with scattered to numerous showers and embedded thunderstorms. The
pressure gradient will remain relatively weak with wind speed on the
order of 10 kt. Prevailing southwest wind today shifts northeast on
Tuesday. A low pressure system emerging out of the central
Mississippi Valley will be monitored for additional precip chances
and potential for an uptick in east/northeast wind mid-week.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....SF
DISCUSSION...CB
MARINE.......TF
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NWS DTX Office Area Forecast Discussion