Snover, Michigan Weather Forecast Discussion

951
FXUS63 KDTX 211756
AFDDTX
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
156 PM EDT Sun Sep 21 2025
.KEY MESSAGES...
- Scattered to numerous showers and thunderstorms today. Greater
coverage and intensity from mid afternoon through evening.
- There is a Marginal Risk of severe thunderstorms. Damaging wind is
the primary hazard.
- Showers continue Monday and Tuesday. Localized heavy rainfall will
be possible.
- Low potential for rainfall Wednesday through next Saturday as a
ridge of high pressure is forecated to build over the northern Great
Lakes.
&&
.AVIATION...
A north to south oriented line of showers will push east of the taf
sites mostly by 19Z today with a lull in showers after that for a
few hours. A warm front located just south of the MI border will
lift through southern MI this evening into tonight, keeping chances
for showers across the area through morning. Timing any periods of
showers will be difficult as there is little agreement between the
models in this moist, weakly forced environment. We`ll continue to
highlight periods with tempo/prob30 as confidence dictates. So far
there has been no thunder over SE MI, and though there is a chance
this evening if we can build some instability behind this line of
showers, confidence/coverage is too low to include in a taf at the
moment. CIGs will largely remain VFR outside of any brief lowering
with showers. There could be MVFR CIGS developing in the morning
south of the front, but soundings still want to stay above 5kft.
For DTW/D21 Convection... This round of showers should end between 19-
20Z with a lull expected later this evening. Chances for showers
continue through morning but we`ll highlight early Monday morning as
the next best chance with more isolated coverage possible this
evening. Low chance for thunder to impact the terminal this evening
but best chance would be before 00Z.
DTW THRESHOLD PROBABILITIES...
* Low for ceilings at or below 5,000 feet today.
* Low for thunderstorms to impact DTW today with the best chance
  would be before 00Z.
&&
.PREV DISCUSSION...
Issued at 1107 AM EDT Sun Sep 21 2025
UPDATE...
Refinement of the shower/thunderstorm forecast is the morning update
topic in terms of timing, coverage, and intensity for this afternoon
and evening. Late morning observations indicate widespread showers
and a rumble of thunder ongoing within a band of isentropic ascent
along and ahead of the larger scale moisture axis advancing across
the Great Lakes. Shower clusters also extend west toward Lake
Michigan at forecast issuance with considerable cloud cover in
between and even farther west into the Midwest states. The slow
eastward pace of this configuration casts additional uncertainty on
how much instability can recover late this afternoon and this
evening. Available hi-res model projections suggest holding out for
some evening recovery as the diffuse front stalled near the IN/OH
border makes a move into Lower Mi this evening. In the meantime, the
forecast update nudges down afternoon high temperatures and adds some
temporal detail to the POP forecast for lower mid afternoon
coverage.
PREV DISCUSSION...
Issued at 256 AM EDT Sun Sep 21 2025
DISCUSSION...
Moisture advection occurs over Southeast Michigan today as the
blocking ridge over the central Great Lakes finally breaks down.
Plan view progs do show low level jet axis already in place for a
good portion of today but precipitation chances will largely hold
off until after 20Z waiting for the main meridional thetae plume on
the 316-324Ke surfaces to release across/through the cwa. Hires runs
show a spread of outcomes today, with some guidance suggesting a
lean/very hit or miss potential. There does remain a signal that
suggests glaciated remnants in the 14-18z time window with a diurnal
re-inititation of showers and thunderstorms then after 20z. It is
this scenario the current Marginal designation in the Swody1 is
predicated on. Current 12hr forecasted PoPs are likely running a
little hot as coverage later today could be fairly sparse. Meager
midlevel lapse rates above what could be a relatively stable low
level environmental profile limits the MLCAPES to 750 J/kg or less.
An inverted V structure to the sounding with 0-6km bulk shear of 30-
35 knots may support a strong to severe thunderstorm today. A wind
gust in vicinity of thunderstorm activity of 40-60mph may be
possible.
A pseudo cold frontal feature is forecasted to organize and be
forced southward through the forecast area tonight. The cold front
will result from the combination of anticyclonic vorticity advection
and dynamic subsidence from confluence aloft. The boundary is
expected to clear Southeast Michigan to the south then stall out in
vicinity of Downriver and western Lake Erie basin for a good portion
of Monday afternoon. Look and feel of the plan view thetae progs
suggest a favorable corridor of frontogenesis and system relative
isentropic ascent across the area. Uncertainty in coverage, but
models do suggest the greatest potential for precipitation and qpf
potential will fall late Monday. Current forecast has categorical
PoPs. Difficult to discuss QPF amounts for individual periods, but
the interquartile range of ensemble data suggests Sunday and Monday
QPF totals of .75 to 1.50 inch will be possible. The real wildcard
is what will occur on Tuesday and some model solutions suggest an
MCV may emerge out of Central United States thunderstorm activity
and track towards the state.
Model trends continue to support a ridge of surface high pressure
building over the northern Great Lakes from Wednesday through next
Saturday. Gradient setup supports a northerly wind direction with
comfortable daytime temperatures near 70. The current forecast has
an extended run of lower PoPs that will likely need to be refined
(lowered).
MARINE...
High pressure over New England gradually departs into the Atlantic,
allowing broad low pressure over the upper Midwest to exert
increasing influence over the central Great Lakes today. Benign
weather early gives way to increasing probabilities for showers and
thunderstorms this afternoon and evening as the low ushers in a warm
front. Isolated stronger storms will be capable of producing
localized wind gusts in excess of 34 knots and waterspouts. Wind
prevails out of the southeast at around 10 kt today, then shifts to
southwest Monday while remaining around 10 kt. An unsettled
showery/stormy pattern continues through Monday into Tuesday as
multiple disturbances pass over the region along with a slow moving
frontal boundary.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....DRK
UPDATE.......BT
DISCUSSION...CB
MARINE.......TF
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at www.weather.gov/detroit.

NWS DTX Office Area Forecast Discussion