727
FXUS63 KDTX 251936
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
336 PM EDT Wed Sep 25 2024

.KEY MESSAGES...

- Dry for the remainder of the day, outside of a low chance (20%)
for a shower, favored in the Thumb.

- Sunny tomorrow with daytime highs in the mid-70s.

- Next chance (30-40%) for rain showers will be Friday night into
  Saturday morning, favored along and south of M59.

&&

.DISCUSSION...

For the remainder of the afternoon and evening... Most locations
remain dry, outside of isolated periods of drizzle or light rain
showers favored over the Thumb, fueled by the pinnacle of the
shortwave trough axis that swings over SE MI over the next several
hours. Outside of this, we reside under non-favorable conditions for
any sustained shower activity. Lapse rates remain shallow under only
a couple hundred joules of CAPE. The extensive field of alto-cu will
wane with the loss of daytime heating, but also with drier air
filtering in from the northwest under increasing mid-level
subsidence within the wake of the upper-level wave.

The Great Lakes will stay situated between two upper-level lows
tomorrow, the first over southern Quebec with the second deep into
the Ohio River Basin. Upper-level confluence and continued support
of mid-level subsidence in the wake of the shortwave will bring dry
weather through tomorrow along with mostly sunny skies. Weak
synoptic flow will bring very little change to the greater thermal
field, however, the boost in insolation will bolster temperatures in
the mid-70s. Attention will then turn to now-hurricane Helene, which
is projected to arrive onshore around Thursday evening. The
aforementioned Ohio Basin upper-level low will retrograde in
response to the approaching tropical system, eventually phasing
before gradually meandering back into the Ohio River Basin through
the weekend. A ensemble heat map of the track density places the
greater cluster of cyclone centers stalling out across northern
Tennessee to southern Kentucky, with a smaller subset (10th
percentile) encroaching into central Indiana/Ohio. This increases
confidence that impacts to SE MI (in terms of QPF) will be on the
lower side.

The EPS/GEFS stamps reveal an initial spoke of enhanced moisture
that pivots over Michigan Friday through Saturday morning, with
moisture lingering over Michigan through the weekend. This will
bring the chance for light rain, favored along to south of M59.
Despite QPF chances trending south of the state line with the 00Z
suite, the 12Z suite has trended rain chances right back right back
over Michigan, which is also observed with the latest ML-models. Will
continue to advertise a chance (30-40%) of showers Friday night into
Saturday morning, favored along and south of M59. A strengthening
pressure gradient in response to the approaching system will also
bring some breezy conditions on Friday across far southern Michigan,
with gusts likely ranging between 25-30 mph.

Otherwise, temperatures stay relatively consistent through the
weekend with highs in the mid 70s, lows in the 50s. Variance across
ensemble members turns higher through Monday-Tuesday regarding speed
and amplification of a trough that drops through the northern
Plains, which will have implications on how fast the residual
moisture from the post-tropical system exits the state.

&&

.MARINE...

Low pressure center is lifting just north of Lake Huron this
afternoon with a northwesterly gradient now spreading across the
lakes. Moisture has all pushed east of the region allowing for a dry
mid week period with high pressure building in from the west. Winds
will decrease 15 knots or less tonight out of the north before
veering around to the northeast on Thursday. As the high pushes off
to the east Friday, low pressure lifts north out of the Southeastern
United States. The pressure gradient will be tightest over Lake
Erie, and gusts of 25 to 30 knots appear likely Friday-Saturday
morning.

&&

.PREV DISCUSSION...
Issued at 1238 PM EDT Wed Sep 25 2024

AVIATION...

Daytime boundary layer growth has led to some clearing of the low
clouds this morning. This trend will continue to some degree into
the afternoon, although additional diurnal cloud development is
likely. The increasing depth of the mixed layer will support cloud
bases being predominately VFR by late this afternoon/evening. A push
of drier air will arrive from the northwest tonight as high pressure
expands in from the west. This will result in an overall clearing
trend during the night. The weakening of the sfc gradient will also
maintain light winds through much of the TAF period.

For DTW/D21 Convection...Thunderstorms are not expected this period.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 feet through this afternoon. Low
  this evening.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

DISCUSSION...AM
MARINE.......AM
AVIATION.....SC


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