FXUS63 KDTX 111025

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
525 AM EST Mon Dec 11 2023


Cold light northwest-west flow this morning should maintain low
clouds (2500-3500 feet) across southeast Michigan. Warming and drying
out of the 850 MB level this afternoon offers up some potential for
clearing skies, but likely going to be sufficient moisture around
3000 FEET to maintain borderline MVFR/VFR clouds into the evening
hours. As winds shift to the southwest this evening and further warm
advection takes place, more defined clearing should take place from
south to north tonight.

For DTW...Don't see cloud bases deviating much from 3000 feet
today, with any partial clearing this afternoon likely refilling back
in for the evening hours. Uncertainty with the exact time of
clearing tonight.


* High for ceiling aob 5000 feet this morning, then lowering
  confidence to low by this evening.


Issued at 303 AM EST Mon Dec 11 2023


Deep layer subsidence amid building heights in the wake of a
departing mid level wave will expand across Lower Mi this morning
and prissiest into tonight. This large scale subsidence will deepen
the low level inversion, which will likely hold the stratus deck in
place into the evening. This and limited low level thermal advection
will keep daytime temps mainly in the 30s today. Low level wind
fields will back toward the southwest tonight and will strengthen.
This will drive a warmer low level airmass into Se Mi, eroding the
low level inversion and allowing for a clearing trend. Despite the
clearing trend, the strength of the gradient flow (1500- 3k ft level
winds of 40-45 knots) will limit nocturnal cooling and support
nighttime lows mainly in the upper 20s.

The backed flow will be in advance of a cold front moving into the
northern lakes tonight. Models have trended a bit stronger with the
amplitude of the mid level trough within the base of a polar low
originating from central Canada and moving into northern Ontario by
Tues morning. This will force the associated surface front all the
way into the Ohio Valley by Tues evening. The larger scale dynamics
will be focused north of the forecast area. Model cross sections
actually indicate the frontal forcing becoming very shallow as it
pushes across Se Mi, even falling apart by the time it pushes south
of metro Detroit. Model solutions also show a fairly significant mid
level dry layer advecting into srn Lower Mi by afternoon. While
there will likely be some low clouds with fropa, a dry forecast
will continue to be warranted on Tuesday. The low level wind fields
along the front will still support fairly breezy conditions. The
strongest wind fields are actually expected within the prefrontal
airmass as opposed to the post frontal cold air advection region.
With the support of model soundings and probabilistic guidance,
peak wind gusts will be kept to 30 MPH, perhaps a little higher in
the northern thumb.

The cold front will usher in a seasonally cold airmass for the
midweek period. Broad sfc high pressure will expand and strengthen
across much of the eastern US during the latter half of the week
within a split mid level flow regime across the CONUS. Most notable
will be the warm air advection within the return flow of this sfc
high which will bring mild air to the forecast area by the end of
the week.


There will be a backing of the winds during the course of the day
and evening ahead of a cold front approaching from the northwest,
forecast to move into far northern Lake Huron Tuesday morning.
Prefrontal southwest winds will become quite strong across Lake
Huron tonight and into Tuesday morning. The potential for gales will
hinge on the degree of mixing to the lake surface as these winds
will drive a warmer low level airmass across the lake. There does
look to be a potential for a period when there is enough over lake
instability to cause some southwest gale force gusts across Saginaw
Bay into central Lake Huron. Current probability guidance is under
50 percent for gusts to gales, however there has been an increase in
the probabilities the last few model cycles. Therefore, a gale watch
will be issued for Saginaw Bay and central Lake Huron overnight into
Tuesday morning. Later forecast shifts will determine if an upgrade
to a warning is needed.

THe post frontal wind fields will not be as strong. There does look
to be a period Tuesday afternoon into Tuesday night where the
gradient increases across the north third of Lake Huron. While there
is a potential for a few brief gusts to gale force, guidance is more
supportive of 30 knot type wind gusts attm.


Lake Huron...Gale Watch from late tonight through Tuesday afternoon for LHZ363-

     Small Craft Advisory until noon EST today for LHZ441.

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



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