085
FXUS63 KDTX 220700
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
300 AM EDT Sat Jun 22 2024

.KEY MESSAGES...

- Flood watch this afternoon-tonight for Midland/Bay/Saginaw
  counties.

- Slight risk of severe thunderstorms this afternoon into tonight
  over much of southeast Michigan, with damaging winds being the main
  hazard, but isolated tornadoes also possible.

- Hot and humid today with high temperatures in the 90-95 range
  south of I-69 with heat indices peaking out just under 100 degrees
  this afternoon.

&&

.DISCUSSION...

Jet forcing tracking through Central Lower Michigan yesterday
afternoon allowed for convection to keep re-firing and track across
the Tri-Cities region, resulting in localized rainfall amounts of 4+
inches. There remains potential training of storms today as the deep
moisture plume hangs around Saginaw Bay (PW values aoa 2 inches) area
and a surface wave then tracks through Central Lower Michigan this
evening. Expecting MLcapes to build to around 1500 J/kg , which will
lead to efficient rain producers, and easily could see 2-4 inches of
rainfall, with isolated higher totals not out the question. Now,
there is some uncertainty if the bulk of the storms will reside just
north of the Tri-Cities, but this set up is worthy of a flood watch
for this afternoon through tonight.

Still looks like locations south of M-59 will be capped during the
day as the mid level dry slot with 700 MB temps of 11 C tracks
through, persisting into the early evening hours. This should allow
the Detroit Metro area and points south to climb into the low to mid
90s with the favorable southwest flow, pushing heat indices to near
100 degrees.

Deep moisture plume coming out the Plains will track through the
rest of the CWA tonight. Significant differences amongst the models
with the strength and placement of the low over northern Lower
Michigan this evening/tonight, but there does appear to be a
consensus with a strengthening low pressure system as it moves
through northern Lake Huron/Georgian Bay. This is concerning, as low
wind shear, both 0-6 km and 0-1 KM will be ramping up with low level
jet in excess of 50 knots developing. Instability/capes may prove
sufficient with 1000-850 MB cape progged to reside in the 500-1000
J/kg range, per NAM. If storms arrive earlier in the evening,
organized severe storms with rotation are in play. SPC day 1 has
upgraded much of southeast Michigan into slight chance. Hopefully, as
the night wears on, the near surface layer will be just stable
enough to keep stronger winds and any rotation above the surface, or
instability could also end up being even more modest and we fail to
generate thunderstorms all together as line approaches the Detroit
Metro Area. Several solutions indicating the line dissipating, with
just some leftover scattered activity along the cold frontal passage
late tonight. However, preference will continue to skew the forecast
toward a broken or solid line of showers/thunderstorms (see RRFS A)
with the good large scale forcing/heights falls/PV advection for
summer standards.

Modest cold advection to follow for Sunday, with 850 MB temps
progged to lowering into the lower teens by Monday morning per 00z
Euro. None-the-less, the 500 MB trough axis swinging through the
Central Great Lakes may still touch off a few showers, mainly over
the Thumb region, as 500 MB cold pool (-15 C) tracks through Lake
Huron.

Warming back up early next week, as shortwave ridging arrives by
Tuesday morning, ahead of a strong northern stream upper level
wave/trough expected to sweep through on Wednesday, triggering storms
and leading to modest cool down for end of the work week.

&&

.MARINE...

Stalled front that has been hovering around southern MI the last
couple days will get pulled back north today generally across Mid MI
which should result in more shower and thunderstorm activity lifting
north today as well. This will also allow southwesterly winds to
spread back across the southern Lakes ushering in another hot
airmass keeping stable conditions across the waters. A stronger,
more organized low pressure system will then track east across
northern MI tonight which will pull a cold front through the region
on Sunday. Increased winds ahead of the front have been topping out
near 25 knots for a couple days now, and continue to do so but
stable conditions and possibly short duration may limit the need for
a small craft advisory but will continue to monitor.

&&

.HYDROLOGY...

Flood watch in effect for Midland/Bay/Saginaw this afternoon into
tonight. The potential exists for repeated rounds of showers and
thunderstorms. Total rainfall amounts of 2 to 4 inches possible with
locally higher amounts not out of the question. With yesterday`s
locally heavy rainfall, flooding would be likely if those totals
verify.

A line of showers and thunderstorms is then expected to spread east
into the rest of southeast Michigan this evening and tonight, and if
these storms hold together, rainfall amounts of half an inch to two
inches can be expected, which may cause minor urban/low lying
flooding. However, the activity may weaken significantly through the
night, and lower rainfall totals under half an inch are not out of
the question by the time the storms arrive over Detroit Metro Area.

&&

.PREV DISCUSSION...
Issued at 1057 PM EDT Fri Jun 21 2024

AVIATION...

An isolated shower or thunderstorm remains possible overnight, but
overall convective potential remains minimal as greater nocturnal
stability gains traction with time. Attention overnight turns to
prospects of fog development as winds lighten and saturation
improves at the surface. MBS appears the most susceptible to a
meaningful visibility restriction in fog, but any location may
witness a brief dip in visibility during the pre-dawn hours. A
northward advancing frontal zone will offer renewed focus for shower
and thunderstorm development Saturday afternoon, particularly across
central lower Mi including the MBS area. Forecast will offer a tsra
mention at MBS/FNT, with diminishing potential with southward extent
from this corridor.

For DTW/D21 Convection...Greater potential for thunderstorms will
focus north of the airspace Saturday afternoon and evening. An
approaching cold front may bring renewed potential late Saturday
night.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms impacting the airspace Saturday night.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch from noon EDT today through late tonight for MIZ047-048-
     053.

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

$$

DISCUSSION...SF
MARINE.......SF
HYDROLOGY....SF
AVIATION.....MR


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