Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251958
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
358 PM EDT Mon Mar 25 2024

.KEY MESSAGES...

- Widespread rain will affect the area late tonight and Tuesday
  morning.

- Showers and scattered thunderstorms are possible late Tuesday
  afternoon and evening with a Marginal Risk for severe weather
  for all of southeast Michigan. Damaging winds will be the main
  threat.

- Windy conditions on Tuesday, with gusts over 35 MPH possible.

- Colder weather returns Wednesday.

&&

.DISCUSSION...

Warm air advection surged into southeast Michigan last night
downstream of the central CONUS longwave trough with 900 mb
temperatures observed at 10C on the 12Z DTX RAOB this morning. The
deep south-southwest flow is also ushering in a fair amount of high
clouds into Michigan. Despite these high clouds, the warmer airmass
is supporting afternoon temperatures into the upper 50s and 60s. The
lower level dry air and influence of the east coast surface high
pressure and upper ridge will support dry conditions through the
remainder of the day.

Michigan will be firmly in the warm sector of the strengthening low
pressure system moving across the mid/upper Mississippi Valley that
eventually lifts into Ontario by Wednesday morning. There will be
very strong wind fields will be surrounding this system. The
poleward oriented 850 mb low level jet (50-60 knots) and 500 mb jet
(125+ knots) will be streaming across MI Tuesday morning. This
anomalously strong jet will be very efficient with moisture
transport as PWATs increase to around an inch for Tuesday morning.
The increasing moisture and ascent will bring widespread rainfall
spreading across southeast Michigan between 2 am and 5 am Tuesday
morning. Boundary layer stability will be the challenging aspect to
the wind gust potential as the warm advection and overnight
inversion likely limits mixing these strong winds to the surface.
However, any areas of heavy rainfall may be able to overcome the
inversion and bring some gusts of 45 mph or greater to the surface
during the morning hours.

The higher moisture/theta-e axis is shunted east of Michigan by a
the strong veering wind field by 15Z along with the arrival of a dry
slot to decrease precipitation chances by late morning and early
afternoon. Will maintain lower end chances for precipitation during
the afternoon as scattered light showers will be possible. A strong
wind field will persist over Michigan during the afternoon, but
forecast soundings suggest an inversion holding throughout the
afternoon. This would again limit the mixing potential even flow of
40-50 knots lingering above the inversion, but gusts will reach 30-35
mph and possibly greater if better mixing can prevail.

A cold front will then drive through Michigan offering a secondary
period of widespread rainfall and a better chance at thunderstorm
activity towards the late afternoon and early evening, roughly 3 pm
to 11 pm. Greater severe thunderstorm potential comes down to the
degree of surface instability that can be maintained into the later
part of the day across southeast Michigan. There will be
exceptionally high shear in place with some hi-res models offering
well over 70+ knots of 0-6 km shear. Lower level shear is on the
order of 25-35 knots and steep mid-level lapse rates of 6-7 C/km.
Some Hi-res models point toward a narrow axis of 100-400 J/kg of
MLCAPE while others offer less than 100 J/kg. Greatest CAPE
potential reaches western portions of the CWA before instability
then wanes towards the eastern portions of the CWA with the loss of
daytime heating. This environment leads mainly to a damaging wind
threat, but the low level curvature in forecast hodographs keeps in
play a low end probability for a weak tornadic spin up. The SPC Day
2 Outlook has been expanded the Marginal Risk across all of
southeast Michigan for tomorrow. The more favored areas for severe
weather would be along and west of the I-75 corridor depending on
the instability trends.

A northern stream wave will be driving into the western Great Lakes
on the back side of the Tuesday system and will evolve into a close
low over Ontario. This will set up the return to cooler conditions
mid to late week with highs generally in the 40s with a return to
the 50s possible by Friday. High pressure should hold mostly dry
conditions through this period.

&&

.MARINE...

Sustained southeast flow will continue to elevated wave heights
across the Lake Huron shoreline into the outer Saginaw Bay, where
Small Craft Advisories remain in effect.

A very strong low level jet (winds at 1 kft of 55-60 knots) will
then surge in early tomorrow morning, just ahead of the arrival of
widespread rainfall, which will overspread across the Great Lakes.
Soundings display an extremely stable over-lake environment with the
antecedent warm air above the cooler waters, which will likely keep
these strong winds just above the surface. However, gradient winds
will ramp as a response to momentum flux, increasing around 30 knots
through the overnight hours. Once the widespread rainfall builds in,
the stable marine layer will weaken, bringing increased chances to
see sustained winds and gusts to gales. Still, soundings are quite
stable even with rainfall, so it is unlikely gusts will be able to
tap into the strongest winds aloft. Gust to gales up to 40 knots are
favored at this time, most likely across north-central to south-
central Lake Huron. A Gale Warning remains in place.

A cold front pivots in late tomorrow night into Wednesday, followed
by high pressure mid-week, bringing quieter marine weather to the
Great Lakes.

&&

.HYDROLOGY...

A potent low pressure system system will impact the Great Lakes
tomorrow with a pair of frontal boundaries set to track through
Michigan. The first round will occur mainly between 4 am and 10 am
tomorrow morning with a quarter to a half inch of rain possible. The
second round will arrive between 3 pm and 11 pm tomorrow with more
variable amounts up averaging to around a quarter inch. Higher
amounts may occur under any strong thunderstorm that may develop.

&&

.PREV DISCUSSION...
Issued at 130 PM EDT Mon Mar 25 2024

AVIATION...

VFR conditions persist today ahead of the incoming low pressure
system tomorrow. Southeast flow continues to strengthen, with gusts
near 20 knots possible across the region today. Strong low-level jet
at about 1000 feet will allow for strong wind shear near the
surface, around 40-45 knots. Flow will continue to strengthen as the
pressure gradient tightens and the low moves to the upper Midwest
tonight into tomorrow. Expecting multiple batches of rain to pass
through the region, with the first beginning around 7Z Tuesday. This
rain will bring below 5000 foot ceilings and borderline MVFR
conditions, especially inside of heavier rain. Chances for lighter
rain exist through the daytime hours behind the initial heavier band
of rain, beginning around 15Z. Confidence is somewhat low on the
extent of lighter rain throughout the day, but ceilings are expected
to drop to MVFR conditions regardless of the presence of
precipitation.

FOR DTW...

Cold front is expected to pass through Michigan between ~21Z-23Z
Tuesday, bringing potential for isolated storms with heavier
rainfall associated. Confidence is low on the extent and timing of
FROPA and the associated storms. Thunder is possible with this later
band of precip, but again confidence remains low at the moment.

DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 feet Tuesday morning.

* Moderate for wind gusts at or above 30kts from ~160 degrees
  Tuesday morning.

* Low for thunder between ~21-23Z Tuesday evening.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Warning from midnight tonight to 10 PM EDT Tuesday for LHZ362-
     363-421-422-441-442-462-463.

     Small Craft Advisory until midnight EDT tonight for LHZ421-441-442.

     Small Craft Advisory until 10 PM EDT Tuesday for LHZ443.

Lake St Clair...Small Craft Advisory from midnight tonight to 10 PM EDT Tuesday for
     LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from midnight tonight to 10 PM EDT Tuesday for
     LEZ444.

&&

$$

DISCUSSION...AA
MARINE.......AM
HYDROLOGY....AA
AVIATION.....BC


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at www.weather.gov/detroit.


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