Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 121700

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
100 PM EDT Mon Mar 12 2018


Areal coverage of IFR/MVFR snow showers will diminish early this
afternoon. None-the-less, lingering scattered snow showers will
likely persist late this afternoon into the early evening hours,
with VSBY dipping into IFR if caught underneath one of them. Warm
pavement temps likely preventing accumulation. Otherwise, light
northwest winds this afternoon, likely not increasing above 10 knots
until this evening. It appears enough low level moisture will linger
this evening/tonight to sustain MVFR ceilings. An isolated threat of
snow showers will persist overnight, but much better coverage and
development expected by Noon tomorrow.

For DTW...Warm pavement temps and surface temps above freezing
likely preventing accumulation this afternoon. Northwest winds not
picking up until this evening, could see gusts around 20 knots
overnight, but especially tomorrow with diurnal mixing kicking in.


* Moderate in ceilings at or below 5000 ft.

* High for snow as precipitation type.

* Very low for northwest crosswind this evening through tomorrow.


Issued at 1051 AM EDT Mon Mar 12 2018


Steady expansion of light snow showers underway this morning,
anchored along the inbound lead mid level trough axis and attendant
surface boundary. Sufficient deep layer ascent exists to sustain a
fairly high concentration of snow showers going forward today. This
process will become increasingly augmented by a diurnal increase in
low-mid lapse rates, as cooler mid level air makes greater inroads
into the region this afternoon. Latest radar trends and recent hi
res model guidance lend confidence for a scattered to numerous
coverage. Increasing depth to the convective layer does suggest the
potential for some higher intensity snowfall rates this afternoon.
This will present the possibility for a good burst to generate a
quick coating of snow and rapid reduction of visibility. However,
given the brief duration and warmer pavement conditions, the overall
accumulation potential remain limited to simply a few tenths.

Minor update to realign pops and snow accumulation slightly based on
recent trends, while nudging forecast highs down a shade.

Issued at 316 AM EDT Mon Mar 12 2018


Persistent high pressure that has resided over the Great Lakes over
the weekend will relent today as an amplifying trough digs south out
of Ontario. The area of PV associated with the tight height fall
gradient and the mid level centered just north of Lake Superior will
meet up with a strip of energy coming off of the southern stream
system in the Ohio Valley. This will result in increased chances for
snow across southeast Michigan this morning, which can already be
seen on radar moving across northwestern lower Michigan. Increased
mid level cyclonic flow will send colder mid level air overhead as a
surface front makes its way through Michigan. Ahead of this front,
low and mid level lapse rates will increase due to daytime surface
heating and aide in sustaining snow activity through the afternoon
and into the evening. Forecast soundings show convective depths
reaching around 6-7k ft, which would create an environment favorable
for heavier snow bursts. Moisture content is not abundant with this
system, but specific humidity values at 700-850 mb will be around
1.5 g/kg this afternoon and evening. Anticipate that any heavy
bursts of snow showers today will be transient in nature. The short
duration of any heavy snowfall in combination with temperatures
being in the mid to upper 30s through much of the event should keep
accumulations limited to around an inch or less.

Secondary wave embedded within the cyclonic mid level flow will dive
south again out of Ontario Tuesday morning and pivot through across
the central Great Lakes. The center of the mid level circulation
will be centered across the central and eastern Great Lakes by
Tuesday afternoon. The associated mid level cold pool will be
rather impressive as temperatures will be around -40C at 500mb.
Combine that with another diurnally driven increase in low to mid
level lapse rates and the result will be in another day of
impressive convective depths, this time around 10k ft. Good lift
through the Dendritic Growth Zone will again favor accumulating
snowfall with the potential for numerous, yet brief, very intense
snow showers to develop. Given the short duration of intense
snowfall, expect that snowfall accumulation will again be around an
inch of less, but locally higher amounts will be possible wherever
the intense snowfall occurs. Models have backed off some with
instability tomorrow, but given the thermodynamics during this time,
would not be surprised to even see a few lightning strikes.

The closed low will move east and up through the northeastern US on
Wednesday and allow northwesterly flow to send slightly colder and
drier air into the region. High temperatures still expected to reach
into the low to mid 30s for Wednesday afternoon. Another trailing
shortwave within the broader trough will pass through the central
Great Lakes Wednesday night. This will result in a slight chance for
scattered snow showers.

Rising heights from a building ridge across the central Plains will
begin to influence the region through the weekend. Still a
difference in model solutions at this time with the evolution of the
ridge and how much increased southwesterly flow pushes warmer air
into southeast Michigan. Either way, it looks like we will at least
get above the 0C mark at 850mb. This will result in temperatures
this weekend increasing into at least the 40s with the potential for
some locations nearing the 50 degree mark.


High pressure will be replaced by a weak and disorganized region of
low pressure forecast to track across Lower Mi and Lake Huron this
afternoon. This will result in light and variable winds for a good
portion of the day. The low will exit to the east of the region
tonight and will weaken with more robust low pressure development
forecast off the east coast. This will support an increasing north-
northwest gradient across Lake Huron during the night. A surface
trough is forecast to drop south across the lake early Tuesday. An
increasing northerly gradient and decent mixing depths will support
gusty winds and waves Tues afternoon and evening, with gusts over
the southern half of Lake Huron possibly reaching 30 knots. Winds
will then gradually weaken Tues night through Wednesday as they
slowly back toward the northwest as the gradient relaxes.


Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.



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