095
FXUS63 KDTX 050542
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
142 AM EDT Sat Oct 5 2024

.KEY MESSAGES...

- Scattered showers and a thunderstorm or two are possible late tonight
  into early Sunday morning in advance of the next cold front. Best
  rain potential looking to occur along/north of I-69.

- Breezy conditions develop tonight and persist through daytime
  Sunday with southwest turning west winds gusting up to 30mph. Some
  35mph gusts possible in the Thumb and Tri-Cities.

- Cold front clears the region by latter half of the day Sunday
  bringing cooler, slightly below average temperatures through the
  first half of next week.

&&

.AVIATION...

VFR conditions will prevail through this TAF period as high pressure
builds across Michigan. Dry air advection should greatly limit the
degree of low clouds or fog as conditions would be favorable
otherwise with mostly clear skies and light winds. Light winds hold
out of the north into tomorrow with a southeasterly wind developing
tomorrow afternoon under clear skies.

For DTW/D21 Convection...Thunderstorms not expected.

DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 350 PM EDT Fri Oct 4 2024

DISCUSSION...

Afternoon water vapor imagery shows the mid-level trough axis
transiting across Lower MI, with visible imagery showing the plume
of mid-level clouds associated with the jet entrance region ahead of
the trough. As the trough axis passes overhead in the next few
hours, subsidence and dry air advection will take over and the
clouds will clear from NW to SE. The inbound high pressure will
dominate tonight, holding stable conditions and clear skies through
the night. Favorable radiating setup brings low temps ranging from
the lower 50s in Metro Detroit to upper 30s in the cool spots of the
interior Thumb and Saginaw Valley. Some patchy frost will be
possible for parts of Midland and Bay County but with limited
coverage and duration will hold off on frost headlines tonight.

A progressive pattern pushes the high east of us on Saturday as the
mid-level ridge axis crests overhead. Stable and sunny conditions
prevail with modest southeast winds. Soundings suggest mixing
heights will come just short of the 850mb temps near 6 to 10 C, so
highs around 70 F look good. The next trough currently making its
way across the Pacific NW will amplify and become a closed low over
the Canadian Prairie provinces on Saturday before tracking into the
northern Great Lakes on Sunday.

The relatively narrow warm sector of this mature system will spread
into the local area Saturday night on a 45+ kt LLJ. An area of
showers will ride in on the nose of this jet between midnight and
daybreak, with the highest coverage occuring within the overlap
between the lower ascent and upper forcing associated with the upper
jet/PVA - most likely to set up along/north of I-69. Mid-level lapse
rates of roughly 7 C/km will result in a narrow corridor of 500 to
1000 J/kg of MUCAPE, supportive of scattered elevated thunderstorms.
The warm advection over the nocturnal boundary layer will bolster
near-surface stability and looks to preclude a severe threat.

The system`s cold front will track east across the area Sunday
morning with additional isolated showers/storms possible along it.
Clouds then clear with mostly sunny and breezy conditions developing
through the rest of the day as drier air works in - westerly wind
peaks around 20 mph with gusts as high as 30 mph. The colder air
mass behind the system will take time to settle in and high temps
actually look to get a slight boost into the mid 70s as the cold
advection and sunny skies induce strong mixing.

The upper low evolves into a larger wavelength troughing pattern
over eastern Canada through the midweek period. This maintains
cooler northwest flow over the Great Lakes which keeps temperatures
slightly below seasonal normals through much of the week. Highs in
the 60s and lows ranging between the mid 30s to mid 40s will be
common. Ensembles favor mainly dry conditions through this period as
intervals of high pressure accompany the confluent flow aloft.

MARINE...

High pressure drifts overhead tonight and Saturday, with
corresponding winds veering from the NW to SE by Saturday afternoon.
Main forecast highlight is the Gale Watch for the northern half of
Lake Huron, including Inner Saginaw Bay to Harbor Beach, for Sat
night-Sun. There is high confidence (70-80%) in gale force gusts
beginning late Sat night for much of Lake Huron in response to a
strong cold front sweeping across the Great Lakes. High confidence
in frontal timing leads to high confidence in onset of these gusts,
which peak near daybreak at ~40 knots. Strong southeast winds will
also elevate wave heights across the open waters to 10-12 feet
during this timeframe. Winds veer to the northwest on Sunday
following the frontal passage, initiating cold advection and
renewing gustiness Sunday evening as mixing heights deepen.
Occlusion of the parent low pressure system however will effectively
weaken the trailing low level jet, so any gale force gusts Sun night
will be infrequent and short-lived. A persistent upper level trough
maintains unsettled conditions through early next week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Watch from this evening through Sunday morning for LHZ361-362.

     Gale Watch from late tonight through Sunday morning for LHZ363-421-
     422-441-442-462-463.

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

$$

AVIATION.....AA
DISCUSSION...TF
MARINE.......MV


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