Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 060853

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
353 AM EST Wed Dec 6 2023


Starting the morning off in a transition region between the
lingering surface trough exiting to the east and high pressure
sprawling across the Plains. This high will drift southeast through
the day with southern MI on the northern periphery of it. There is
plenty of low level moisture between these systems as noted by the
wealth of stratus all across the Great Lakes especially in the wake
of the lakes. Though it is not completely overcast as there are also
several pockets of clearings within this region, especially over SE
MI. As this pattern shifts southeasterly today, winds will flip from
northwesterly to westerly which will give the moisture on the west
side of the state a push eastward through SE MI. There are some obs
reporting light rain which pairs well with regional satellite, so
question is...what happens when this plume passes over SE MI today?
Most likely we`ll go overcast for a while but there is a chance we
could squeeze out some drizzle as the moisture is below the DGZ and
surface temps are reaching into the upper 30s. As this shouldn`t be
impactful and is low confidence to occur, will leave out of the
forecast at this point and see how well we saturate with the morning
sounding and satellite trends before adding to the forecast.

The upper levels offer the next chance of precip, mainly for Mid MI
and the northern Thumb as a short wave tracks through the developing
northwest flow. The longwave ridge over the the western and central
conus will be sliding eastward while this low amplitude shortwave
rounds the ridge and tracks across Lake Huron tonight. Narrow
corridor of fgen along the pv filament will largely stay over
northern lower and Lake Huron, but there is a signal for a band of
low level convergence off the lake to get pushed through mid MI and
the Thumb which could be enough to spark a few light showers as the
low level jet passes overhead. Moisture quality with the warm
advection is questionable once again with some degree of saturation
up to around 7kft, but that becomes nearly isothermal around -5C
which won`t be enough for snowflakes. So hedged overnight chance
pops to a rain/snow mix but QPF looks to be a trace anyway so only
impact would be a glaze on roads if temps drop quickly to below 32.

Fairly quiet for the end of the week Thursday and Friday as the
ridge axis passes overhead  opening the door for deep southwesterly
flow and warm air advection. 850mb temps rise to around 7C which has
led to highs forecast in the upper 40s to around 50 with partly
cloudy skies. Meanwhile, a strong trough is getting carved out over
the western conus with a 140 knot jet streak helping strengthen it
further while it advances across the Plains. The original mid level
and surface lows will be located up over western Ontario with a long
cold front then extending south to Texas. Won`t get overly detailed
at this point, but models have been pretty consistent with
advertising a mid level shortwave exciting a surface low along the
front which would track north through the Midwest Saturday. this
keeps the warm sector over SE MI resulting in warm temps again but
moisture advection along the front from the Gulf with a trough
pivoting to a negative tilt and a very dynamic upper level trough
and jet looks to produce a round of rain showers, and possibly
thunderstorms, across lower MI Saturday into Saturday night. Though
its early, the trend over the last couple days has been a westward
shift adding confidence to the warm solutions, but there are a few
days left this week where additional shifts are likely/possible.

Sunday is in question as to how fast the surface front sweeps
through leading to low confident high temps. A surge of cold air
digging southeast will race in for the afternoon while lingering
wrap around moisture and upper level trough keep precip chances
around. 850mb temps dropping to around -10C or lower (per ECMWF)
would lead to a changeover to snow.



High pressure builds in today, maintaining light winds that
gradually back to the southwest as the surface ridge axis slides
overhead and a warm front lifts through the region. A weak low then
clips northern Lake Huron overnight, supporting a period of wet snow
for mainly the open waters before exiting into Ontario by mid-day
Thursday. Will see some constriction to the pressure field as this
system glances through, which further organizes and strengthens the
southwest gradient Thursday. Standard concerns for the Saginaw Bay
channel to see elevated wave heights in the SW flow regime, thus
Small Craft Advisories are in effect from the Bay to Harbor Beach.
Southerly winds ramp up again on Friday as strong low pressure
develops upstream. This system brings potential for heavy
precipitation, initially as rain Saturday with a possible transition
to snow Sunday/Monday dependent on the low track. Early indications
suggest a tight gradient on the backside of the low and a much
colder airmass, so this will be a window to watch for potential
gales Sunday-Monday.


Issued at 1207 AM EST Wed Dec 6 2023


The low cloud clearing trend progressed steadily during the evening
leaving the northern fringe of borderline MVFR/VFR just south of DTW
leading up to midnight. Northerly low level wind maintains dry air
between the lakes during the late night as broad high pressure
builds in from the Plains by morning and moves steadily through SE
Mi during the afternoon. Cloud trends over Lake Huron and Michigan
will be monitored while a favorable NNW wind holds much of the
morning. A general backing trend in wind direction then occurs as
the surface high slides eastward and this brings Lake Michigan
supported MVFR stratus back into SE Mi by afternoon into Wednesday

For DTW... Clear to scattered cloud cover holds through the morning
with sub 10 kt NW wind. Wind backing toward the west in the
afternoon leads to sub 5000 ft ceiling in the afternoon and
borderline MVFR by Wednesday evening.


* High for ceiling 5000 feet or less Wednesday afternoon.


Lake Huron...Small Craft Advisory from 10 PM this evening to 4 PM EST Thursday
     for LHZ421-441.

     Small Craft Advisory from 10 PM this evening to 10 AM EST Thursday
     for LHZ422.

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



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