638
FXUS63 KDTX 241009
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
609 AM EDT Tue Sep 24 2024

.KEY MESSAGES...

- Seasonable temperatures through the early and mid week period.

- Showers are likely today and tonight, with a chance of non-severe
thunderstorms.

- Most areas will receive around a half inch of rain or less, but
localized totals in excess of 1 inch will be possible.

- A few widely scattered showers possible Wednesday. Otherwise,
drier conditions through the rest of the week with temperatures
trending back above normal.

&&

.AVIATION...

Widespread IFR ceilings to start the morning with a warm frontal
boundary and approaching low pressure. Column saturation peaks
within the next hour two supporting LIFR at a few terminals.
Ceilings then lift to MVFR midday with low-end potential to briefly
cross the VFR threshold before descending to IFR (and perhaps LIFR)
again tonight. Several rounds of showers are expected throughout the
day with varying degrees of rainfall intensity which could result in
brief IFR visibility reduction. Additionally, an embedded rumble or
two of thunder cannot be ruled out after 18Z, although temporal and
spatial uncertainty preclude any PROB30 adjustments at this time.
Light northerly winds veer toward the east-southeast today, then
southwesterly as the low departs, and eventually west-northwesterly
Wednesday morning as the warm front also exits.

For DTW/D21 Convection...Showers today and perhaps a few
thunderstorms this afternoon and evening, but low confidence on
timing and duration as precipitation remains scattered.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 feet today and tonight.

* Low for thunder after 13Z today, then medium from 22-03Z.

&&

.PREV DISCUSSION...
Issued at 321 AM EDT Tue Sep 24 2024

DISCUSSION...

Broadening corridor of northward moisture transport underway in the
form of extensive cloud cover and some pockets showers early this
morning. This process governed by a modest increase in mid level
southwest flow immediately downstream of pending height falls tied
to an elongating upper trough set to arrive late today. These
conditions will largely define much of the daylight period, as
interludes of greater isentropic ascent working across the advancing
elevated warm frontal zone contribute to intervals of generally
light shower production. Insolation potential minimized with a lack
of sun, while the low level gradient holds from an easterly
direction. This ensures a limited diurnal temperature response,
capping afternoon temperatures in the upper 60s to lower 70s.
Prospective secondary convective response between 20z and 03z along
the east flank of the surface low and warm frontal intersection
offers greater potential for a brief uptick in rainfall intensity.
General consensus of model sounding data shows meaningful depth to
the instability with a skinny cape profile, with upwards of 1000
j/kg of mlcape nosing across the Ohio border. Limited residence time
of any clusters will preclude a greater flooding threat. Given the
track of the surface low, a localized increase in both magnitude and
depth of shear remains plausible across far southern sections. While
the lack of greater magnitude of destabilization would seemingly
work against establishing deeper rotating updrafts and a
corresponding sig wx threat, the pattern from a synoptic level gives
pause and remains worthy of monitoring as future CAM cycles and
observational trends arrive.

Amplifying mid level trough trailing the lead wave arrives
Wednesday, effectively drawing the cold front across southeast
Michigan through the day. Modest frontal convergence in the presence
of sufficient moisture quality and diurnal destabilization points to
widely scattered shower development targeting the late day period.
No meaningful airmass change this period, as temperatures again push
into the 70s.

Benign weather conditions for the late week period. Deep column
drying with increasing stability Thursday as mid level northwest
flow briefly exists atop surface high pressure. A 589 dm upper high
then takes residence Friday, ensuring moderating temperatures with
continued dry conditions to finish the week. Attention shifts to the
south as a large closed system centered over the mid/lower
Mississippi valley interacts with a tropical system forecast to make
landfill over the eastern Gulf coast sometime Thursday. Southeast
Michigan still likely outside the main influence of this height fall
center at least early during the weekend period, but with rainfall
chances steadily climbing as the system lifts east by the latter
half of the weekend. Further revision to precipitation chances
expected.

MARINE...

Light east-southeast winds (mainly 10-15 kts) this morning as an
area of low pressure tracks through the Central Great Lakes late
today and tonight, maintaining the lighter winds. Numerous showers
with a slight chance of thunderstorms will accompany the low. Large
area of high pressure building in Wednesday night-Thursday will lead
to light northwest winds, becoming northeast to end the work week as
the high moves off into Eastern Canada and low pressure lifts north
out of the Southeastern United States. The pressure gradient will be
tightest over Lake Erie, and gusts reaching at or above 25 knots
appear likely Friday-Saturday morning.

HYDROLOGY...

Low pressure brings scattered to numerous showers and a chance of
thunderstorms today and tonight. Basin average rainfall is forecast
to be between one quarter and one half inch, but totals in excess of
1 inch will be possible where any training storms develop. Flooding
is not likely but there is the potential if any heavier rainfall
axis does develop over the urban corridor.

&&

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

$$

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


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