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000
FXUS63 KDTX 240347
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1147 PM EDT Tue Apr 23 2024

.KEY MESSAGES...

- Breezy late tonight with gusts up to 30 mph in the Thumb.

- A Freeze Watch is in effect for all of southeast MI late Wednesday
  night through early Thursday morning as overnight lows dip into
  the upper 20s.

- Rain chances increase Friday night as a series of lows lift into
  the upper Midwest. There is low confidence in shower and
  thunderstorm potential Saturday and Sunday.

&&

.AVIATION...

The region of rain showers with a few lingering thunderstorms will
exit to the east of the terminals by 06Z.  Low level moisture
advection in the wake of this area of rain will increase the
probabilities for MVFR based cloud development. An upper wave will
drive a cold front across the area overnight. There will be a
veering of the winds to the north-northeast with the passage of this
front. Post frontal cold air advection and ample low level moisture
will sustain widespread MVFR based stratus well into Wed morning. A
little bit of post frontal moisture and flux off Lake Huron will
contribute to some light rain/snow showers or drizzle from PTK
northward Wed morning.

For DTW/D21 Convection...The showers and isolated thunderstorms will
be be exiting the airspace between 04Z and 06Z per recent
observational trends. A push of colder air will arrive within
strengthening north winds after 12Z Wed morning. Wind gusts will top
20 knots.

DTW THRESHOLD PROBABILITIES...

* High in ceilings aob 5000 overnight into early Wed afternoon.

&&

.PREV DISCUSSION...
Issued at 349 PM EDT Tue Apr 23 2024

DISCUSSION...

Frontal forcing has lifted into southern lower Michigan, with a band
of steady rain filling into Lenawee and Monroe Counties as of
issuance. This band is expected to hold along/south of I-94 before
shearing southeast late this evening. Attention then turns to the
cumulus field upstream across northern lower MI-WI-MN where
convective cells have been developing over the past couple hours
invof the mid-level wave and trailing cold front. Expectation is for
these showers and thunderstorms to move into the Tri Cities and
Thumb region between 22-00z (6-8pm local) and track southeast across
the rest of the cwa tonight. Steep mid level lapse rates approach 8
C/km upstream, which will advect into northern portions of the cwa
and be the main catalyst for a stronger updraft or two this evening.
Widespread strong storms are not expected, however, as low
instability will struggle to maintain updrafts in such high shear.

The upper level trough and surface front will slide southeast into
Lake Erie by daybreak Wednesday, ushering out any lingering showers.
Breezy conditions linger through the morning, especially around the
Thumb region where gusts may approach 30 mph. Morning lows will
reflect post-frontal cold advection, as some spots around the Tri
Cities and Thumb will see temperatures near freezing and wind chills
in the teens. Standard subsidence inversion settles between 3.0-5.0
kft agl, initially trapping leftover moisture and maintaining a
thick stratus deck for the morning. A much drier low level airmass
then advects south Wednesday afternoon, dropping PWAT values below
0.25" (below the 10th percentile per SPC climo) and quickly mixing
out clouds by afternoon. H8 temperatures dropping into the single
digits during the day leads to a range of temperatures from near 40
degrees in the Thumb to low 50s for inland and urban locations.

Dry weather persists through mid-day Friday as heights build and a
roughly 1030 mb surface high stalls overhead. Opportunities for
cloud cover remain limited, with just a glancing stream of high
cloud moving in Thursday invof a low amplitude wave. Main concern
during this time window is sub-freezing temperatures (upper 20s)
Thursday morning, in which a Freeze Watch has been issued overnight
Wednesday through Thursday morning.

Benign conditions come to an end Friday afternoon as the next storm
system ejects out of the Plains and into the Upper Midwest. The
primary circulation will stay well to our west, but will push the
warm conveyor and associated moist isentropic upglide right overhead
by Friday evening. A strong low level jet, 40-45 knots at 850 mb,
contributes to substantial warm advection and moisture transport
into the area at this point, increasing confidence in a period of
widespread rain Friday night and a gradual warm up through the
weekend. Temperatures Saturday and Sunday look to climb comfortably
into the 70s.

Precipitation prospects for the weekend offer much less certainty,
beginning with a mid-level dry slot that arrives Saturday morning.
This creates a highly conditional convective setup in which
available long-range guidance struggles with depth and magnitude of
static stability within the dry slot. If the atmosphere is dry and
capped (e.g. 00z Euro), convection would struggle to initiate and be
reliant on a warm/moist boundary layer that may not come to
fruition. On the other hand, favorable return flow and opportunity
for the SE CONUS ridge to direct embedded shortwaves toward lower MI
(e.g. 12z GFS) Saturday and Sunday will warrant monitoring for
thunderstorm potential.

MARINE...

A Small Craft Advisory will expire at 4 PM today as gusty winds and
heightened waves diminish into the evening hours. Surface low
pressure associated with an upper level disturbance crossing the
Midwest has shifted south, becoming more diffuse over The Straits as
a secondary surface low emerges further west. Expect some additional
rounds of showers this evening, including the potential for a few
thunderstorms that could result in locally higher winds/waves. Most
of the convective activity should develop ahead of the system`s cold
front through before colder post-frontal air filters overnight. This
leads to brisk northerly flow and low-end potential for gusts to
gales while lapse rates steepen and forecast soundings are well-
mixed once stronger LLJ winds clip central Lake Huron. Will likely
issue another Small Craft Advisory for Saginaw Bay and The Thumb
with the evening marine update. Gradient winds trend lower midday
Wednesday before high pressure starts building into the Great Lakes.
More favorable marine conditions are expected Thursday with
sustained ridging until Friday. Unsettled weather returns Saturday,
dependent on trajectory of a large low pressure system ejecting from
The Plains.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Watch from late Wednesday night through Thursday morning for
     MIZ047>049-053>055-060>063-068>070-075-076-082-083.

Lake Huron...Small Craft Advisory until 10 PM EDT Wednesday for LHZ421-422-
     441>443.

Lake St Clair...Small Craft Advisory until 10 PM EDT Wednesday for LCZ460.

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

$$

AVIATION.....SC
DISCUSSION...MV
MARINE.......KGK


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