996
FXUS63 KDTX 040520
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
Issued by National Weather Service Gaylord MI
120 AM EDT Wed Jun 4 2025

.KEY MESSAGES...

- Rain chances increase Wednesday: Locally heavy rainfall possible.
  Maybe a severe weather risk?

- Gusty pre-frontal winds tonight/Wednesday.

- Questions regarding lingering rain chances for Thursday/Friday...
  drying trend into Saturday.

&&

.AVIATION...

VFR conditions are expected to persist through 12Z at all TAF sites.
CIGs are then expected to lower from northwest to southeast
Wednesday morning into the afternoon in association with rain
showers and isolated thunder chances along/ahead of a cold front
dropping across the state. As discussed by the previous forecaster,
thoughts still align with these rain/thunder chances arriving at MBS
first (most likely before 18Z), and then the other TAF sites around
18Z and after. Similar timing is expected with lowered CIGs,
although low MVFR/IFR CIGs may not reach DTW/DET/YIP until after 00Z
Thursday. Strong winds off the surface w/ weaker winds at the ground
also keep LLWS in the TAF through tonight before south-southwest
surface winds increase through the morning ahead of the front.

For DTW Convection: Aforementioned front will help generate showers
and isolated storms later this afternoon, potentially impacting DTW.
Best chances for any strong storms appear to be between 19Z-00Z, but
shower/storm chances look to continue through tonight. Will continue
with PROB30 in the TAF given uncertainty in timing and storm
coverage at this time. Lightning, hail, and gusty winds will be
possible with any strong storms.

&&

.PREV DISCUSSION...
Issued at 345 PM Jun 3 2025 by National Weather Service Gaylord MI

DISCUSSION...
Pattern Synopsis/Forecast: Large scale pattern features mean troughing
across western North America...and a narrow trough just off the eastern
seaboard with a ridge axis in between centered over the Great Lakes.
Western trough is split with a couple pieces of energy in the southern
branch (off the southern California coast/over the central High
Plains).  Western trough is also drawing deep moisture northward from
the Gulf with 1.50+ inch precipitable water values all the way up into
Lake Superior...along with a nice low level thermal ridge with +15C at
850mb off the 1200Z DTX sounding.  But the sounding was also quite dry
to start with double digit dew point depressions from the surface on
up.  At the surface...a cold front extends from James Bay southwest
across western Upper Michigan/northwest Wisconsin/central Iowa...with
high pressure over the mid Atlantic helping funnel warmth and
increasingly moist air into the upper Lakes.

Height falls ahead of upstream trough already spreading into the upper
Lakes this afternoon...and will continue to advance east tonight.
Associated cold front will be knocking on our doorstep by daybreak
Wednesday...and will be slow to push through southeast Michigan as main
upper level energy gets shunted northeast and what remains of the front
becomes more parallel to the upper level flow.  Mean trough axis
remains upstream of the region Thursday as pattern gets a bit more
blocky over the Atlantic...frontal boundary remnants will probably be
lurking not too far to our south as a result while a weak high pressure
bubble sets up across the upper Lakes for Friday.  Remnants of upstream
trough should get pushed across the region Saturday...as a jet streak
comes over the top of a blocking high over the eastern Pacific and digs
into western Canada.  The resulting cyclonic shear spins up an upper
level low that looks to take aim on the upper Lakes early next week.

Primary Forecast Concerns:

Rain chances increase Wednesday...locally heavy rainfall possible.
Maybe a severe weather risk?:  Bulk of the rain chances should hold off
until Wednesday morning...evolution suggests some sort of anafront rain
band with a good bit of precipitation occurring behind the front along
frontogenetic axis and aided by right rear jet quadrant dynamics. Can`t
rule out some pre-frontal elevated convection across southeast Lower
Wednesday morning...but this evolution does open up a window for
destabilization especially for far southeast Lower where MLCAPE values
in the 500-1000J/kg are possible.  Unidirectional wind profiles would
support bowing segments/damaging winds mainly along/east of an ADG-BAX
line after 1700Z.  As mentioned above front is going to be slow to exit
southeast Lower...combined with an axis of 1.50+ inch precipitable
water values and a vertical wind profile supportive of echo training
some locally heavy rainfall is also possible through Wednesday night.

Gusty pre-frontal winds tonight/Wednesday: At least somewhat...as a
southwesterly 40-50kt low level jet develops tonight as the boundary
layer decouples.  This makes for some interesting wind gust probability
evolution as local probabilistic guidance suggests 30-50 percent
probabilities for advisory level gusts (39+kts) tonight north of the
Detroit metro area...but probabilities drop off dramatically Wednesday
morning with the onset of heating/mixing.  This suggests (to me anyhow)
that the probabilistic guidance is trying to grab low level momentum
that due to stability may not actually be there for the taking.  Expect
winds will remain up tonight just due to the gradient and gusts of 20-
30mph north of I-69 not unreasonable at all.  More widespread gusts of
25-30+mph will develop Wednesday morning...gradually tapering off from
northwest/southeast during the afternoon with the cold frontal passage.

Questions regarding lingering rain chances for Thursday/Friday: What
remains of Wednesday`s cold front looks like it should be south of the
state Thursday morning...but the fingerprints of the lingering
baroclinic zone will still be there across Indiana/Ohio.  Will have to
linger some low rain probabilities from the I-69 corridor south for
Thursday...but the probabilities around I-69 should taper off during
the afternoon with drier weather the farther north you go.  Thursday
night will probably continue to feature small rain chances from I-96
south to the Ohio border.  Friday is a bit more of a question mark as
consensus forecast tries to nudge PoPs farther north during the
afternoon...operational GFS tries to push a more substantial mid level
short wave trough in our direction Friday though it shows hints of
being convectively enhanced so I`m somewhat wary of this idea.  But the
forecast trends for Saturday look dry for now.

MARINE...

South to southwest winds will continue tonight gusting 25 to 30kts.
Winds will veer northwest Wednesday in the wake of a cold front and
diminish to less than 15kts. Northwest to north winds are expected
Thursday and Friday at or below 15kts.  North winds Saturday will
switch to southerly on Sunday and will increase to 15 to 25kts.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 6 AM EDT early this morning for LHZ421-
     422-441>443.

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

$$

AVIATION.....DJC
DISCUSSION...JPB
MARINE.......JPB


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