576
FXUS63 KDTX 130925
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
525 AM EDT Mon May 13 2024

.KEY MESSAGES...

- Clusters of showers and a few thunderstorms move west to east over
the area while diminishing coverage this morning.

- Showers and thunderstorms redevelop this afternoon and continue
tonight mainly north of metro Detroit. Locally heavy rainfall is the
primary hazard while storms otherwise remain below severe intensity.

- Showers and thunderstorms continue Tuesday, increasing coverage
toward Detroit while decreasing coverage north to south from the Tri
Cities area.

_ After a round of slightly below normal temperatures Tuesday,
readings rebound warmer with dry weather Wednesday and Thursday.

&&

.AVIATION...

VFR conditions hold through the day as a frontal boundary stalls
over central MI later this morning resulting in mainly mid/high
cloud over SE MI. This front becomes the focal point for additional
shower/storm redevelopment this afternoon-evening, mainly confined
to MBS and FNT. Rain gradually expands southward over the course of
this evening as the front sags south, eventually reaching the
Detroit terminals overnight. Increasing low level moisture with
column cooling behind the front affords the potential for ceilings
to lower towards or into MVFR territory with this later day/night
rain. Breezy conditions likely during the daylight hours with gusts
peaking in the 20-25kt range out of the SW. Winds weaken with the
loss of sun late this evening and eventually turn to NNE late
tonight-early Tuesday post frontal passage.

For DTW/D21 Convection... Main convective potential holds north of
the airspace through this afternoon. This changes later this evening
as the front gradually sags south shifting convection likewise
south. While there is a low chance for showers or a storm tonight
over DTW (currently advertised in Prob30 group), better rain chances
come early Tuesday morning. This timing is expected to greatly limit
any thunderstorm development as the front, and any instability,
will be pushing south of the terminal around this point.

DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 357 AM EDT Mon May 13 2024

DISCUSSION...

Showers and thunderstorms rode strong elevated moisture transport
across Lower Mi during the late night. Earlier activity showed peak
intensity on the leading theta-e gradient where 00Z model analysis
fields indicated a 40-50 kt low level jet around the 850 mb level.
Resulting nocturnal instability and shear were and continue to be on
the weak end of the spectrum with 700-500 mb lapse rate hovering
around 6.5 C/km within a wind profile of sub 20 kt effective bulk
shear. Any lingering storms in this environment have a pulsey
character with a few higher reflectivity flare-ups until exiting into
Ontario by early morning.

After the early morning convection, a stray shower is possible until
peak heating ramps up this afternoon and as the low level moisture
axis settles west to east across southern Lower Mi. The cold front
still becomes the focus for a new round of surface based convection
with some clarity on the frontal position in central Lower Mi by mid
afternoon peak heating. HREF mean MUCAPE peaks around 1000 J/kg
during the 18-21Z time period limited primarily by sub 6 C/km 700-
500 mb lapse rate within a similarly low shear wind profile. A pulsey
storm mode is the favored with coverage north of metro Detroit both
this afternoon and tonight, on target for the SPC general thunder
outlook. Metro Detroit is expected to stay dry today after getting
brushed by activity early this morning. Some breaks of sun across the
warm sector allows a run into the lower 80s for afternoon high
temperatures.

The latest 00Z model cycle remains in good agreement on the larger
scale scenario projecting the front to stall in southern Lower Mi
tonight. This frames locally heavy rainfall as the primary concern
as severe storm parameters remain muted while a broad plume of PW in
the 1 to 1.5 inch range builds across the area. The front stalls
while the southern stream low pressure system moves into the mid MS
valley but is not yet close enough to reach this far north with its
own rainfall. New convection in southern Lower Mi then remains
frontally forced while transitioning to a nocturnal and elevated
character focused mainly north of the surface frontal position,
along and north of the I-69 corridor up through the Tri Cities and
northern Thumb. Bulk weather features continue to have above average
predictability while convective trends carry more uncertainty
regarding coverage, intensity, and total rainfall. The current 00Z
HREF mean QPF has a similar placement but is noticeably lower
compared to 24 hours ago, less than 1 inch for the 12 hr period, and
is likely a reflection of the weaker larger scale forcing. Mid level
flow within the frontal zone decreases to 20 knots or less but still
with some frontogenetic packing of theta-e surfaces and some weak
northern stream entrance region jet support. These conditions will
be sufficient to hold borderline numerous to widespread coverage of
showers and storms in the forecast. Locally heavy rainfall will also
stay mentioned but with no further advancement of the message for
now.

Mostly shower coverage with a few thunderstorms fill in Tuesday
morning south of I-69 through metro Detroit to the Ohio border as
the southern stream mid level circulation and surface low move into
the Ohio valley. The northern fringe of the system`s rainfall
pattern reaches into southern Lower Mi while pulling the front
steadily southward across the area. The potential for heavy rainfall
during this time is diminished by lower rainfall intensity and the
steady movement of the front. Eastward progression of the low
pressure system carries showers south of the Ohio border shortly
after midnight Tuesday night after rainfall averaging 0.5 inch in 12
to 18 hours.

Mid week model projections have cooler and drier weather building
into Lower Mi with high pressure Wednesday and Thursday. Extended
range global runs then exhibit similar timing of arrival for the
next low pressure system in the Great Lakes Thursday night and
Friday.

MARINE...

Northern stream low pressure stalls over Hudson Bay this morning,
slowly sinking a cold front into the Great Lakes region. The front
has already been a focus for showers and embedded thunderstorms
overnight, and will continue to be a favorable corridor for showers
and storms throughout the day into this evening as it settles
across Saginaw Bay-central Lake Huron. Meanwhile, a cutoff southern
stream low lifts toward lower MI this evening in turn causing
expansion of showers and a few thunderstorms from southwest lower MI
into southern portions of the marine zones late tonight. Slow
progression of the southern stream low maintains unsettled
conditions on Tuesday, with prevailing northeast flow established by
Tuesday evening as the front drifts south. Onshore component of the
flow and some enhancement to the gradient provides an opportunity
for Small Craft Advisory conditions later Tuesday before high
pressure builds in mid-week to support drier and calmer marine
conditions.

HYDROLOGY...

A cold front is on schedule to become the focus for an active shower
and thunderstorm pattern in southeast Michigan today through
Tuesday. Locally heavy rainfall is the primary concern as the front
stalls across the region tonight. Showers and thunderstorms will be
numerous along the front, especially tonight from I-69 northward,
resulting in locally heavy rainfall totals around 1 inch by sunrise
Tuesday. Predictability is greater on the overall rainfall scenario
(numerous showers and some thunderstorms along the front), but still
low on precisely where the rainfall axis will line up. The latest
guidance data suggest the front stalls north of M59 while the
rainfall axis sets up from I-69 northward. A broad area of minor
flooding potential is centered on the time period from tonight
through Tuesday morning when ponding of water on roads and in other
prone areas will be possible.

&&

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

$$

AVIATION.....KDK
DISCUSSION...BT
MARINE.......MV
HYDROLOGY....BT


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