137
FXUS63 KDTX 081954
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
354 PM EDT Wed May 8 2024

.KEY MESSAGES...

- Much cooler on Thursday with rain expected south of M-59 and a
chance north.

- Next chance of showers and thunderstorms comes Saturday.

&&

.DISCUSSION...

A flattening shortwave ridge sliding over southern MI today in the
wake of Wednesday`s low has lead to a mostly sunny and mild day with
temps well into the 70s. A lingering trough axis draped across
northern lower this afternoon has lead to an enhance cloud field
which will impact locations as far south as the northern Thumb,
otherwise diurnal cu shouldn`t last too long across the rest of the
area. As temps attempt to drop off tonight, elevated clouds start
filling in north of the stalled cold front just south of the state
which will limit the mins to around 45-50 degrees.

Tonight marks the beginning of a bigger shift in the weather pattern
as a very positively tilted trough drops out of eastern Canada while
digging westward and phasing with the orphaned upper low over the
northern Plains. Remnant mid level wave will then advance along the
trough with a weak surface low tracking east along the front on
Thursday. Moisture advection up the elevated portions of the front
lingering over southern MI will result in a period of rainfall for
most of the CWA. Two main questions will be when does the rain move
in and how far north will it extend? Most guidance suggests the lead
edge of the deeper moisture will push north across the Ohio border
after 06Z tonight with northerly flow feeding dry air in the lower
levels beneath the stout low level inversion which will take some
time to saturate. A narrow corridor of higher theta e air will
advance north to around I94 while fgen flares up after about 15Z
which should lead to more moderate showers. Fgen higher on the front
makes it up to Saginaw but with a good deal of dry air still in the
soundings up to 10kft. Even so, hires suite offers a good duration
of light rain through the day so will hedge forecast a little to
keep a slight chance or chance pop going up there for now. Rain will
taper off after dark with the deformation pulling east away from the
area. QPF up to around a third of an inch is expected.

Friday should be dry with another short wave ridge sliding SE
through lower MI. Northerly flow will keep cool air filtering into
the area keeping highs muted in the lower 60s. The next chance of
rain comes Saturday as a narrow trough slides SE through the Great
Lakes out of Canada. There will be a brief flip around to SW flow
ahead of this system which may be able to bring a bit of moisture
into the area, but PWATs are only expected to get just above a half
inch. Light flow keeps shear minimal, less than 20 knots but there
is some potential for a couple hundred joules of MUCAPE so can`t
rule out some thunderstorms. The progressive pattern brings ridging
back for Sunday.

&&

.MARINE...

Weakening surface low has drifted well to our east, with its
attendant cold front washing out overhead. For the Great Lakes, this
has corresponded to winds veering to the north while stable open
waters have kept gusts below 25 knots. Closer to the shoreline where
land influence comes into play, winds may gust to around 30 knots
before subsiding later this evening in which Small Craft Advisories
are in effect. Elevated portions of the frontal boundary remain
orphaned overhead to reactivate shower activity by Thursday morning
across western Lake Erie/Lake St. Clair, with a slightly cooler
airmass overhead once again introducing wind gusts to 25 knots
Thursday afternoon. Weekend weather remains unsettled precipitation-
wise owing to broad troughing aloft, but the overall wind field
remains light.

&&

.PREV DISCUSSION...
Issued at 138 PM EDT Wed May 8 2024

AVIATION...

Breezy westerly flow with gusts of 25 to 30 knots is in place this
afternoon across Southeast Michigan this afternoon as flattened
ridge is suppressed to the Southeast United States. Surface high
pressure is shown to build southward in response to differential
heating and mesohigh forcing which will in turn cause a cold front
to backdoor off Lake Huron and Lake St Clair this evening. Expect an
abrupt wind shift with winds turning to the northeast around 01-02Z.
A deep upper level trough axis will then settle into portions of
northern Lower Michigan Thursday. Increased midlevel deformation and
frontogenesis is expected to result in a widespread coverage of rain
showers after 15Z for all of Southeast Michigan.

DTW THRESHOLD PROBABILITIES...

* Low in crosswind thresholds being exceeded this afternoon.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422-
     441>443.

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

$$

DISCUSSION...DRK
MARINE.......MV
AVIATION.....CB


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