913
FXUS63 KDTX 100751
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
351 AM EDT Wed Jul 10 2024

.KEY MESSAGES...

- A Flood Watch remains in effect for much of the area from the I-94
  corridor north through tonight as the remnants of post-tropical
  storm Beryl bring widespread moderate to heavy rainfall to the
  region.

- Heaviest rainfall is expected now through 9 AM. A brief lull in
  coverage or intensity possible during the late morning, with a
  second round of heavier rainfall expected in the afternoon through
  roughly 6 PM, focused more north of I-94.

- A period of above average temperatures is expected to begin this
  weekend into early next week.

&&

.DISCUSSION...

Post tropical cyclone Beryl has now arrived over the Ohio River
Valley, and will bring extended periods of moderate to heavy
rainfall to SE MI through the day as the system progresses northeast
into southern Michigan and eventually Lake Erie and Lake Ontario.
MIMIC-TPW satellite imagery showcase PW values around 2", which is
in-line with model derived projected values around 2.10-2.20". These
near record values (99.5th percentile w.r.t climatology) are a
direct result of a massive amount of Gulf derived moisture that has
accompanied Beryl.

Ongoing rainfall is a result of this initial surplus of near record
moisture values along the nose of the downstream jet (now pinching
into the Metro region), coupled with increased low level
frontogenetic forcing that is aligning north of the low pressure
system, which at present is maximized from roughly southern Lake
Michigan to Alma. Additional difluent flow aloft along the nose of
an upper-level jet is also providing lift through the upper-reaches
of the atmosphere, directly over SE MI. From now through roughly 12Z
(8 AM), this frontogenetic forcing/deformation zone will start to
increase in strength in the lower levels and will pivot deeper into
SE MI, generally north of I-94 but south of Midland/Bay Counties.
This will bring rainfall rates on the order of .25"-.50" per hour
through the mid to late morning hours. Concurrently as the center of
this system starts to encroach into southern Michigan, a deep mid-
level dry slot will briefly pinch into the Metro region. This will
not outright end rain chances, but can act to decrease coverage and
intensity across the Metro region and possibly for locations north,
through the late morning hours. Several hundred joules of MUCAPE do
build in during this time frame, so some isolated thunderstorms are
not out of the question.

The dry slot will quickly pivot east out of Michigan during the
early afternoon as the system centers over Lake Erie, where wrap
around moisture will continue to interact with the strong
deformation zone, maintaining or reinvigorating the production of
moderate to heavy rain showers into the afternoon and early evening.
The deformation axis is expected to again hold over SE MI, along or
just north of I-94, to just south of Midland/Bay counties. The
deformation axis is expected to wane after 21Z (5 PM), but lingering
rain will hold in through the late evening, especially closer to the
Thumb, tied to the better moisture axis. All rain associated with
this system is expected to move out early Thursday morning.

Last, low-level modeled soundings show neutral to slightly unstable
profiles. Sporadic gusts of 25-35 mph will be possible today,
especially with any thunderstorm activity. Ensemble guidance shows a
few outliers of 40 mph gusts in a higher-end scenario.

Rainfall totals of 2-4" are expected across the greater portion of
SE MI, particularly where the aforementioned deformation axis sets up
and holds. ECMWF Shift of Tails, a measure of extremities comparing
of the ensemble QPF output from the top ten percent of M- Climate, is
showing extreme values over SE MI -- not a major surprise with a
post-tropical system directed over us, but it does highlight SE MI
(and SW MI) as the locations most susceptible to higher-end
precipitation totals for today. A Flood Watch remains in effect for
all counties outside of Monroe and Lenawee. An upgrade to portions of
the Flood Watch to a Flood Warning will be possible, pending
presentation of radar/satellite imagery combined with monitoring of
in-situ observations.

High pressure will fill in behind the system, but will maintain a
20% chance for an isolated shower as an upper-level trough swings
over the state tomorrow. Low end PoPs hold on Friday as well with
the trough axis clearing by Friday evening, before a shortwave ridge
builds in by Saturday. Temperatures return back into the mid-80s
through the weekend.

&&

.MARINE...

Remnants of Beryl continue to move into the region today and bring
heavy rainfall. Flow strengthens overnight as low pressure center
nears and brings a tighter pressure gradient overhead. Strong
onshore flow will develop as a result, with wind speeds of 20-25
knots over Lake Huron, gusting up to 30 knots. As a result, Small
Craft Advisories have been issued for the nearshore zones of Lake
Huron and the Michigan waters of Lake Erie. Lake Erie will see Small
Craft Criteria earlier than Lake Huron with more southeasterly flow
closer to the center of the low, and the advisory is in effect until
10 AM today. For Saginaw Bay to Port Huron, the advisory is in
effect starting 8 AM this morning.

The low pressure center will move over Southeast Michigan/Western
Lake Erie this afternoon, veering winds to the west over Lake Erie
while maintaining northeast flow over Lake Huron. This may
reinvigorate breezy conditions across Lake Erie and possible Lake
St. Clair. Strong winds are expected to die down Thursday with the
departure of the low. Winds will back to the northwest as high
pressure takes over.

&&

.HYDROLOGY...

A Flood Watch remains in for all of southeast Michigan through
tonight, except for Monroe and Lenawee counties.

Widespread moderate to heavy rainfall will continue through the
morning and afternoon hours. As the center of post-tropical storm
Beryl moves into Lake Erie this afternoon, the band of heaviest
precipitation is expected to pivot to a more southwest to northeast
orientation, aligning the heaviest rainfall potential north of I-94
but south of Midland/Bay counties and northern Thumb (Huron County).
All locations across SE MI will still be susceptible to periods of
intense rainfall, however, the longer staying power of this wider
band of rainfall brings increasing chances to see 2-4 inches of
total accumulation by early tomorrow morning. There is also a chance
for isolated to scattered thunderstorms during the late morning and
early afternoon, favored across the Metro region and south towards
the Ohio border, which can produce highly localized elevated
rainfall totals.

Flooding concerns are elevated through today, especially for small
streams, creeks, and flood prone locations. Flooding may also
occur in poor drainage and urban areas

&&

.PREV DISCUSSION...
Issued at 1201 AM EDT Wed Jul 10 2024

AVIATION...

Widespread rainfall from the remnants of the tropical system Beryl
brings deteriorating conditions through the early tomorrow morning
hours. Ceilings will quickly fall to IFR before sunrise with
visibilities under areas of heavier rainfall down to 2SM or less.
Heavy rainfall will be the prevailing condition with a chance for
thunderstorms. Targeting the 07Z to 11Z window for thunderstorms
based on downstream observations. Northeast winds will be gusting to
25-30 knots throughout the morning and afternoon as the main surface
low arrives over Lake Erie by late afternoon. Conditions may improve
slightly during the afternoon, but will maintain IFR ceilings
and lighter shower activity into the evening.

For DTW/D21 Convection... Remnants of tropical system Beryl will
dominate the conditions through today. There will be a chance for
thunderstorms and will initially target the 07Z to 11Z window for
the D21 airspace based on observations across IN and OH as this
activity lifts into lower Michigan.

DTW THRESHOLD PROBABILITIES...

* Low to Medium for thunderstorms early this morning.

* High for cigs aob 5kft early this morning through this afternoon.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch through this evening for MIZ047>049-053>055-060>063-
     068>070-075-076.

     Beach Hazards Statement from 8 AM EDT this morning through this
     evening for MIZ049-055-063.

Lake Huron...Small Craft Advisory from 8 AM this morning to 10 AM EDT Thursday
     for LHZ421-422.

     Small Craft Advisory from 8 AM this morning to 4 PM EDT Thursday
     for LHZ441>443.

Lake St Clair...None.
Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EDT this morning for LEZ444.

&&

$$

DISCUSSION...AM
MARINE.......BC
HYDROLOGY....AM
AVIATION.....AA


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