767
FXUS63 KDTX 221900
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
300 PM EDT Sun Sep 22 2024

.KEY MESSAGES...

- Showers through the evening hours.

- More seasonable temperatures Monday through Wednesday with showers
likely once again on Tuesday.

&&

.DISCUSSION...

Neutral to negative tilted upper level trough tracking through
Ontario/northern Great Lakes while a secondary, more subtle
shortwave, tracks through the Midwest. An attempt of a coupled jet
structure (right entrance/left exit region) over southeast Michigan.
Regardless, with the southern left exit region being the main driver
and with the good moisture axis (PW values of 1.5+"/700 MB dew pts
near 5 C/850 dew pts 12+ C) advancing through the CWA this evening,
widespread showers are expected with some modest instability
allowing for a slight chance of embedded thunderstorms.

Another round of showers likely for Tuesday as shortwave trough and
associated weak surface low tracks through Lower Michigan. 12z Euro
remains one of the more bullish solutions.

Strong upper level Jet (140 knots at 250 MB) tracking through
British Columbia on pace to dive south through the Plains on Monday.
Although there is some merger of heights with the upper level wave
coming out of the Four Corners region, the main height fall center
and subsequent closed 500 MB low looks to reach the southern
Mississippi River Valley Tuesday night-Wednesday, which will likely
capture the tropical system in the Gulf of Mexico. However, at this
time, it appears a blocking upper level ridge (588+ DAM at 500 MB)
will be building over the Great Lakes region to end the work week,
supporting dry weather into Friday.

&&

.MARINE...

A low pressure system and trailing cold front will bring widespread
rain showers and possibly some embedded thunderstorms through the
afternoon and evening hours. After the passage of the front, winds
will flip to the north and will increase up to 20 knots sustained,
with gusts to or just shy of 25 knots. These elevated winds will be
most likely across Lake Huron, and will push wave heights to around
4 ft around the tip of the Thumb. A Small Craft Advisory will be in
effect through tomorrow due to elevated wave heights.

High pressure then briefly fills in on Monday bringing lighter winds
and dry weather, but a second low pressure system will move right
over the central Great Lakes Tuesday afternoon into Wednesday
morning, bringing the likely chances for showers and embedded
thunderstorms.

&&

.HYDROLOGY...

Showers with a slight chance of embedded thunderstorms to move
through southeast Michigan this evening. Basin average rainfall
looks to be under half an inch. However, given PWATs greater than
1.50 inches, locally higher amounts to 1.00 inch can not be totally
ruled out.  No significant flooding is expected regardless.

&&

.PREV DISCUSSION...
Issued at 138 PM EDT Sun Sep 22 2024

AVIATION...

An area of showers is moving across western Lower Michigan early
this afternoon associated with strong moisture advection ahead of a
cold front. The core of heavier precipitation is set to spread across
terminals in the 20Z to 22Z time frame with a few leading isolated
light showers. High coverage of VFR mid-high clouds will begin this
TAF period with ceilings and visibilities falling initially to MVFR
as main moisture surge arrives. Conditions will continue to
deteriorate tonight with IFR conditions tied closer to the front as
it moves into southeast Michigan. There will be potential for pockets
of LIFR ceilings by early tomorrow morning as well. Winds of 5 to 10
knots will carry through the afternoon with a veering to the west in
the immediate wake of the front late tonight and then more northerly
takes hold across all terminals by around 12Z tomorrow morning.
Expecting at least MVFR restrictions to hold through tomorrow morning
at northerly flow maintains low level moisture.

For DTW/D21 Convection...A few embedded thunderstorms will be
possible as rain spreads across D21 airspace later this afternoon
through the evening. The isolated nature will preclude mention in
TAFs at this time.

 DTW THRESHOLD PROBABILITIES...

* Medium for ceilings at or below 5000 feet by 01Z Monday, then high
  through tonight and into Monday morning.

* Low for thunderstorms from 22-07Z this evening.

* Low for ceilings at or below 200 feet early Monday morning.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 2 AM to 10 PM EDT Monday for LHZ421-441.

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

$$

DISCUSSION...SF
MARINE.......AM
HYDROLOGY....SF
AVIATION.....AA


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