Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 132246

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
646 PM EDT Tue Mar 13 2018


Scattered snow showers within unsettled northwest flow will persist
into the evening, but gradually diminish in both intensity and
coverage. Local IFR vsbys and MVFR cigs can be expected until this
activity ends in the 02z-04z time frame. VFR conditions are then
expected for the rest of the forecast period with a decided lack of
low level cloud cover late tonight into Wednesday. Northwest flow,
which will gust to near 20 knots early in the forecast will back to
the west/southwest on Wednesday.

For DTW...Aside from passing snow showers producing MVFR conditions,
generally expected lower VFR cigs. This activity will end after 02z
or so and cigs should steadily lift thereafter into Wednesday.


* High for ceilings aob 5000 ft this evening, low overnight.


Issued at 342 PM EDT Tue Mar 13 2018



As of 340 PM EDT...Scattered to numerous snow showers continue
across much of southeast Michigan, aided by enhanced lake aggregate
moisture and increased lift from a midlevel impulse/cold pool aloft
(-35 to -40 C at 500 hPa) traversing the region. Most of this
activity has largely been benign in nature, as the cellular nature of
the activity coupled with transient movement and March sun angle
will limit accumulation potential, despite favorable lift in the DGZ
and deep convective depths (5+ kft). The exception continues to be
across the eastern Thumb, where an earlier more robust lake-enhanced
band produced 2-4 inches of snow across eastern Huron and Sanilac
counties. This activity has transitioned to more of a cellular nature
as well with embedded heavier brief squalls as daytime heating has
primarily taken over as the forcing mechanism as the midlevel impulse
drifts off to the southeast. With snow still ongoing, will allow the
Winter Weather Advisory for Huron, Sanilac, and St. Clair counties
to continue through 8pm, and will continue to monitor trends for a
possible early cancellation.

Across the rest of southeast Michigan, still expecting to see the
scattered to numerous snow showers continuing into the evening
hours. Embedded pockets of more moderate to perhaps briefly heavy
snow will be possible, especially between 4-7pm coinciding with the
peak diurnal heating response. These embedded heavier bursts could
lead to a quick couple tenths of an inch of accumulation as snowfall
rates perhaps reach a half of an inch per hour in the heaviest snow.
Rapid reductions in visibility below a mile will also be possible,
with a coating of snow to perhaps a few tenths on roadways (limited
again by March sun angle) creating enough of a threat to continue
mentioning potential hazardous and slick travel conditions the rest
of this afternoon and through the evening commute. Will continue
issuing Special Weather Statements as needed to highlight the
hazardous travel threat.

Activity rapidly wanes after sunset with loss of daytime heating,
but another renewed Lake Huron band may form overnight as
convergence is enhanced with winds becoming more west/northwest as a
secondary weaker midlevel impulse passes by. Will have to watch the
exact placement of this potential band closely as eastern portions
of Huron and Sanilac counties may get clipped with another couple
inches of snow. After daytime highs struggling to reach the freezing
mark for most locations, low temperatures will be on the chilly side
as skies begin to clear out towards daybreak from west to east as
drier air filters in. Low temperatures will range from the upper
teens to lower 20s.


Drier air will continue to filter into the region during the day
Wednesday with a brief period of dry weather as shortwave ridging
attempts to crest over Michigan. This will allow for a period of
scattered to perhaps few clouds especially Wednesday afternoon.
Winds will shift more to a westerly direction and with minimal
temperature advection, high temperatures will largely be driven by
solar insolation, and expecting temperatures to reach into the mid
and upper 30s for most areas.

A weak surface trough will pass across the region late Wednesday
night and into the day Thursday bringing flurries and scattered
light snow showers to portions of the region (mainly near Lake
Huron). Accumulations will be negligible well under an inch. An
increase in cloud cover accompanying the surface trough will allow
Wednesday night lows to only fall into the mid and upper 20s. High
pressure will begin to ridge in from the northwest Thursday night
with drier weather returning. High temperatures Thursday will range
from the mid and upper 30s with low temperatures Thursday night
falling back down into the upper teens to lower 20s.


Strong NWP consensus that the closed polar low centered around
Ontario or Quebec will persist into next week, reinforced by a round
of height falls over the West Coast. The net result locally will be
temperatures generally on the cool side of normal with persistent
confluent NW flow aloft favoring high pressure at the surface and a
reduction in precipitation episodes. Occasional brief window for
slightly warmer temps will exist as energy peels off the circulation
out west and transits the central CONUS, but any response to the
thermal or forcing fields over SE Michigan are likely to be
suppressed as cyclonic flow anchored over Canada never fully
relinquishes its grip on the Great Lakes.


Scattered snow showers over southern Lake Huron, St Clair and Lake
Erie will come to an end tonight.  Moderate gusty northwest flow
will gradually begin weakening Wednesday while backing to a more
westerly component.  Small craft advisory conditions will continue
in the nearshore of Lake Huron and outer Saginaw Bay through
Wednesday afternoon.  Another cold front will swing through the
lakes Wednesday night veering winds back to a northerly direction
along with scattered snow showers through the end of the week.
Large high pressure will bring lighter westerly flow along with fair
weather for the weekend.


MI...Winter Weather Advisory until 8 PM EDT this evening for MIZ049-055-

Lake Huron...Small Craft Advisory until 4 PM EDT Wednesday for LHZ421-441>443.

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



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