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afddtx

Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
534 am EST Tue Nov 12 2019

Aviation...

A much colder and drier airmass today will support prevailing VFR
conditions within a sct to bkn coverage of diurnally enhanced
stratocu. Downstream penetration of lake moisture may offer
a limited window for light snow showers or flurries to emerge late
in the day (best chance mbs), resulting in brief MVFR should
activity materialize. Deeper diurnal mixing should be able to
support a few winds gusts around 20 knots. Very cold airmass, with
light west-southwest flow tonight off of Lake Michigan may support
transient borderline MVFR/VFR cigs but confidence is low and will
carry just scattered group.

For dtw...subsidence/drier air will move in at the start of the taf
period to support breaks in the clouds, with variable VFR low
clouds likely during the day.

Dtw threshold probabilities...

* high for precipitation type of snow.

* Low for ceiling aob 5000 ft.

&&

Previous discussion...
issued at 300 am EST Tue Nov 12 2019

Discussion...

Current Lake effect snow bands over the Southern Lake Huron basin
are gradually becoming re-aligned north to south, but will remain
on/near the Sanilac/St Clair County shoreline into parts of the
morning hours. Another dominate lake effect band extending along the
western shore of Northern Lake Huron will pivot south this morning
and clip at least Huron County before shifting southeast over the
open waters. Will adjust timing of the Winter Storm Warning to end
at 17z (noon) for these three counties to account for additional
snowfall beyond 09z. This could amount to 2 to 4 inches locally
given the current intensity of elements within each of these main
bands. Further west, will allow the warning for Tuscola County and
advisory for Lapeer and Macomb counties to expire as remaining snow
showers continue to weaken and generally become more and more
scattered in nature as Main Lake effect shifts east during the early
morning.

The Arctic airmass that will dump into the area in behind this
system still looks to set record low maximums today and record low
temperatures tonight. In fact, given the respond over northern lower
Michigan early this morning (below zero in clear area between lake
effect cloudiness), will lower tonight's low temperatures several
more degrees as generally clear skies should develop as ridging
translates through the area. Highs will once again stall in the 20s
on Wednesday, but rather cold low maximum records will preclude any
additional record setting cold for this airmass. For more details on
temperature records over the next few days, refer to the climate
section of this discussion below.

A shortwave is still expected to drop southeast into the area on the
west side of upper through left in the wake of the current exiting
winter storm system. This will produce a period of light snow late
Wednesday into Wednesday night with accumulations expected to be
less than an inch. While temperatures will moderate from the record
territory, additional cold air in the wake of this next shortwave
will maintain chilly conditions through the last part of this week.
This will be accentuated by the widespread snow cover now in place
over lower Michigan. Highs Thursday/Friday will range in the lower
to mid 30s.

The next shortwave within northwest upper flow on the west side of
the upper trough will bypass the area to the north, but more cold
air will filter into the area as a large high pressure system passes
just north of the region. This will maintain temperatures in the 30s
over the weekend with a moderation begin in the Sunday to Monday
time frame as an airmass of Pacific origin is able to slip into the
area along the southern edge of polar airmass positioned over Canada.

Marine...

Small craft advisories remain in effect today as strong northerly
winds persist over Lake Huron, gusts to around 30 knots will occur
over central portions. In addition, the cold air will continue
produces numerous bands of lake effect snow squalls until the wind
gradually shifts northwest Tuesday afternoon. Wind diminishes with the
center of high pressure tonight before quickly increasing again from
the SW during Wednesday ahead of the next low pressure system. The
low and associated cold front move through the central Great Lakes
Wednesday and Wednesday night with another round of snow and
moderate west wind Post cold front. This system is quickly followed
by another Arctic front that could push northwest wind gusts to gales over
the open water of Lake Huron on Friday.

Climate...

Current records for those dates are below:

Record low maximums for November 12/13

Detroit area....31/21 (1995/1911)
Flint area......28/19 (1995/1986)
Saginaw area....30/21 (1995/1986)

Record lows for November 12/13/14

Detroit area...16/12/13 (1983/1911/1986)
Flint area.....15/12/12 (1997/1986/1986)
Saginaw area...16/12/11 (1920/1986/1933)

&&

DTX watches/warnings/advisories...
Michigan...Lakeshore flood advisory until 4 am EST Wednesday for miz048-049-
054-055-063.

Winter Storm Warning until noon EST today for miz049-055-063.

Lake Huron...Small Craft Advisory until 4 am EST Wednesday for lhz421-441>443.

Lake St Clair...Small Craft Advisory until 10 am EST this morning for lcz460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 am EST this morning for lez444.

&&

$$

Aviation.....Sf
discussion...dg
marine.......sf
climate......dg

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