Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 070832

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
332 AM EST Wed Dec 7 2016


First of a series of fronts rotating around a stacked low pressure
system is currently sweeping across lower MI. The low is currently
over Ontario but will be slowly shearing SW to NE across the Great
Lakes as a jet streak tracking through the base of the trough
creates height falls across the Ohio Valley which stretches out the
mature low. This first front will start the shift in the weather
pattern locally ushering in the first phase of cooler air. 850mb
temps will fall to around -5 to -10C today with westerly flow cold
air advection out of the northern Plains and Midwest. Even with CAA
over Lake MI, lake effect will struggle to reach eastern MI as
convective depths struggle to reach 4kft with the unfavorable
east/west fetch across the lake. Still could see some afternoon
flurries but don`t expect accumulations today. High temps will only
be in the mid 30s today.

A second weak front will pass through Thursday morning ushering the
next level of cold air into the region as 850mb temps fall further to
-10 to -15C. Model soundings show convective depths increasing
slightly but still lacking the good fetch over the water to saturate
enough to make it to the east side of the state. Do expect the
flurries or light snow showers to increase in coverage with the
colder air Thursday morning. A stronger trough rotating around the
back of the exiting low will sink south through MI Thursday evening.
This will veer winds to the northwest thus increasing the fetch over
the lakes. Convective depths also look to increase further possibly
to around 7kft. In addition, the trough will lay out west to east
across the favorable I 94 corridor early Thursday night which could
add a necessary forcing mechanism to get a lake effect band to
stretch into the area. This time frame will be highlighted at the
best chance to see some light accumulations of snow. Hires models
are advertising a second band extending south into the Saginaw
Valley area from near Traverse City. Updates likely as models come
more in line. Highs Thursday will struggle to hit 30F.

Shortwave ridge will slide over on Friday while a surface low tracks
across the Ohio Valley. This will lessen the chances of lake effect
but cold air will remain locked in place with highs again staying in
the upper 20s.

The next notable system will make landfall from the Pacific on
Friday, targeting the Great Lakes Saturday night through Sunday
night. As cyclogenesis commences over the plains, ridge
amplification over MI will bring about southerly flow and warm air
/moisture advection. Models still struggle to converge on a solution
for the strength of the low and depth of the upper level trough that
will develop as the system is still days away from being sampled
with upper air instrumentation. They have however stuck with the
timing for the most part and the idea that a system with a good deal
of moisture will pass through the area for the latter half of the
weekend. Currently, thermal profiles are leaning toward colder
solutions which would lead to mainly a snow event.



Well mixed westerly flow has developed over the Great Lakes region
in the wake of the cold front that pushed through last evening.
Westerly wind gusts of 30 to 34 knots are expected today, with any
marginal gusts to low end gales being brief and highly localized.
Will adhere to consistency and forgo the issuance of a Gale Warning.
Small craft advisories remain in effect until Thursday morning as
frequent gusts of 25 to 30 knots continue. Winds will shift to the
northwest and gradually diminish Friday. Winds are forecasted to be
relatively weak on Saturday as high pressure slides through the
region. Winds to strengthen out of the south again on Sunday.


Issued at 1158 PM EST Tue Dec 6 2016


A broad area of low pressure with moderate intensity over northern
Ontario will supply colder air over Lower Michigan for the next few
days. The first stage of the colder air will come in during the
early morning on westerly surface wind gusting around 20 knots. MVFR
ceiling associated with this air mass will cover most of Lower
Michigan through afternoon and into Wednesday evening. Some
shallowness in the cloud moisture is indicated in forecast data
which offers potential for a few breaks in coverage at times. The
best chance for meaningful breaks will be over the DTW corridor
which will be on the southern fringe of lake effect influence as the
wind pattern shifts slightly from west toward southwest through the
day. The gusty west to southwest surface wind will be the only other
element of significance in the absence of anything more than a snow
flurry through the period.

For DTW... Westerly wind gusting around 20 knots will bring colder
air into the region that will maintain MVFR for the most part
through Wednesday evening. DTW will be on the southern fringe of
lake effect influence which could result in some substantial breaks
of VFR but which are difficult to time at this point in the

//DTW Threshold Probabilities...

* High for ceiling 5000 ft or less with some breaks during the early
  morning. Moderate during afternoon into Wednesday night.


Lake Huron...Small Craft Advisory until 10 PM EST Thursday FOR LHZ421-422-

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



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