950
FXUS63 KDTX 120945
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
545 AM EDT Sun May 12 2024

.KEY MESSAGES...

- Temperatures return to near normal values today and a few degrees
above normal Monday.

- Showers and scattered thunderstorms move in late tonight and
Monday as a cold front drops through the region.

- Locally heavy rainfall is possible Monday afternoon and Monday
night as the front stalls across southern Lower Michigan.

- Showers and thunderstorms continue Tuesday as the front exits the
region. Cooler than normal temperatures follow Tuesday and Wednesday.

&&

.AVIATION...

Low pressure is finally vacating to the east early this morning with
clear skies across all terminals. Weak area of high pressure drifts
overhead today maintaining VFR conditions with cloud cover confined
to mid/high cloud streaming in from the northern Great Lakes. High
also keeps winds on the lighter side, at or below 10kts, through the
bulk of the daylight hours today as they rotate from NW to SW by
early Monday morning. Some remnant showers or thunderstorms are
possible late tonight (~05-11Z) as prior day upstream convection
along the cold front tracks into SE MI. Best potential is over the
northern sites (FNT/MBS, perhaps down to PTK) with chances looking
limited for the Detroit sites- removed rain mention in current TAF
as a result. Confidence in thunder isn`t high enough for mention yet
for the northern sites so will continue to run with SHRA. Frontal
timing and subsequent shower/storm chances has slowed in guidance,
not fully arriving until the latter half of Monday outside the
current forecast window

For DTW/D21 Convection...Remnant convection along the cold front
over the northern Great Lakes looks to track into at least portions
of SE MI late tonight. While there is a low shot that it reaches as
far south as Detroit, majority of guidance suggests the remnants
hold from PTK-north. For the northern portions of the D21 airspace,
how much thunder remains within this activity carries a fair degree
of uncertainty as supporting instability wanes.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 feet today.

&&

.PREV DISCUSSION...
Issued at 353 AM EDT Sun May 12 2024

DISCUSSION...

Sunshine through patchy cirrus starts the day across SE Mi as weak
high pressure slides through the central Great Lakes. The high is
then shunted quickly eastward as the next sizable low pressure
system moves from central Canada to the upper Midwest and northern
Great Lakes by afternoon. An expansive pattern of warm advection
precedes the system first noted as a further increase of cirrus
coverage and then late morning to early afternoon thickening mid
level clouds across southern Lower Mi. Moisture transport/theta-e
advection is adequate for the cloud cover but a bit too shallow for
rain this far south, although radar indications of virga are likely
toward the Tri Cities. Temperatures finally return to near normal
conditions for early/mid May with the help of SW wind gaining
traction across the area, however afternoon highs are held in check
by the early expansion of cloud cover. Boundary layer growth likely
comes up short of the 800 mb shown in model soundings that would
otherwise support a larger 70+ temperature footprint. Preference
leans toward slightly cooler guidance leading to afternoon highs in
the upper 60s most areas.

SW flow continues to support mild conditions tonight as the system
warm sector builds fully across the central Great Lakes while also
setting up at least somewhat receptive conditions for late arriving
showers and thunderstorms. Upper Midwest activity developing off
this afternoon`s diurnal cycle has a chance to survive the evening
and reach SE Mi after midnight, although on a steady weakening
trend. Model projections of surface based instability drop off in
typical nocturnal fashion while 700-500 mb lapse rate hovers in the
6-7 C/km range. More notable is the 40 kt warm sector low level jet
setting up within the 850 mb theta-e ridge having potential to
support scattered elevated convection by late evening both in the
warm sector and then closer to the cold front as it settles into
northern/central Lower Mi toward sunrise. Inherited entry level
likely/numerous POPs cover this well from the Tri Cities and
northern Thumb down to the I-69 corridor by sunrise Monday.

The front entering northern Lower Mi Sunday night is still projected
to stall somewhere in central to southern Lower Mi during Monday
ensuring an active early week period across the region.
Predictability is higher than average on the larger scale weather
structures such as the presence of the frontal zone in general, the
James Bay and KS/OK mid level circulations, and the 1 inch PW
moisture supply between them. The combination of these elements is
favorable for increased confidence in a heavy rainfall scenario but
with low predictability on QPF location and magnitude. The pattern
will have a substantial convective component, both surface based and
elevated/nocturnal, which will also be able to manipulate the
effective position of the larger scale front. Assuming those
uncertainties and taking the 00Z model consensus at face value
favors a potential heavy rainfall area generally north of the M-59
corridor and south of the M-46 corridor from Monday afternoon
through Monday night.

The southern stream wave brings surface low pressure into the Ohio
valley by Tuesday and this gives the front a chance to become more
progressive north to south across Lower Mi. Showers are likely with
a chance of thunderstorms along the front but farther south toward
metro Detroit and the Ohio border region. If we again assume the
latest model timing then this activity moves south of the border
Tuesday evening. A dry period during mid week allows time for some
recovery before another system moves in during the late week period.

MARINE...

High pressure slides across the central Great Lakes this morning. It
brings favorable marine conditions until another low approaches late
in the day. This system offers the potential for enhanced southwest
flow over Saginaw Bay where gusts could briefly touch 25 knot Small
Craft Advisory threshold. Otherwise, showers and storms arrive
across Lake Huron and Lower Michigan tonight and continue through
the early week period as a cold front stalls across the area.

HYDROLOGY...

An active period of weather will be centered on a cold front moving
into Lower Michigan late tonight which then stalls in central to
southern Lower Michigan Monday and Monday night. Showers and
thunderstorms will be numerous along the front, especially Monday
afternoon and Monday night, when locally heavy rainfall possibly
exceeding 1 inch is possible. Predictability is moderate on the
overall rainfall scenario but still low on precise threat areas and
total amounts needed to factor in for flooding hazards. A broad area
of minor flooding potential is centered on the Monday night time
period for Southeast Michigan.

&&

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

$$

AVIATION.....KDK
DISCUSSION...BT
MARINE.......DG
HYDROLOGY....BT


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.