Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 070457
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EST Wed Dec 6 2017


.AVIATION...

Extensive canopy of low VFR stratus will remain entrenched across
the southeast Michigan airspace through Thursday. This environment
will support episodic bouts of flurries overnight and early
Thursday, but with conditions remaining unfavorable for a greater
response that would result in some accumulation and/or visibility
restrictions through this time. Some uptick in the coverage of
light snow showers/flurries may occur coincident with the passage of
a mid level wave Thursday afternoon. There will be the potential
for a brief reduction in visibility with any heavier bursts.

For DTW...low VFR stratus firmly in place through Thursday. Periodic
flurries overnight/early Thursday. Window for an increase in light
snow shower coverage exists Thursday afternoon, where a brief
disruption to visibility is possible.  Little to no accumulation is
currently expected.

//DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less through Thursday afternoon.

&&

.PREV DISCUSSION...
Issued at Issued by National Weather Service GRAND RAPIDS MI/

DISCUSSION...

Water vapor imagery shows a couple features of note rotating around
the broader upper low centered just south of Hudson Bay. The first
is a small PV max zipping across southern Lower MI at this time with
trailing subsidence. Beneath this subsidence we see lake effect
clouds over northern and central Lower MI spreading southeast into
the forecast area.

An even stronger PV max has entered IA as part of a broader area of
enhanced PV rotating around the low. As this feature approaches Lake
Michigan, the boundary layer and convective instability will both
grow, as seen with increasingly negative theta-e lapse rate
forecasts. A gradient in this instability develops and stretches
eastward roughly along the I-94 corridor Thursday morning into
afternoon, suggesting low level fgen is in play with drier and
colder air wrapping around the lake. Convection allowing models have
been consistent in depicting organized banding of the snow as is
already depicted farther north at this time with the Gaylord radar.

Although accumulations over southeast Lower MI will be curtailed by
the long distance from Lake MI, we are looking at a potentially
impactful setup Thursday morning into the afternoon with rapid
localized changes in travel conditions around I-94/I-96/I-69 related
to visibility and icing. Additionally, this will be the first event
of its kind in quite a while.

The next uptick in snow is expected Friday night into Saturday as a
compact PV max drops south along Lake MI before rotating across the
Ohio Valley. This will continue to be a familiar refrain through the
week as the mean upper low moves little through the period and a
succession of PV maxima rotate through.

MARINE...

Southern Lake Huron buoy observations indicates wind gusts are
dropping to 35 knots in spite of favorable channeling scenario along
Saginaw Bay with southwesterly flow. We have therefore cancelled the
Gale Warning.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until midnight EST tonight for LHZ422.

     Small Craft Advisory until 7 AM EST Thursday for LHZ421-441.

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

$$

AVIATION.....MR
DISCUSSION...NWS GRAND RAPIDS
MARINE.......NWS GRAND RAPIDS


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at www.weather.gov/detroit.



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