Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 010812

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
312 AM EST Thu Dec 1 2016


Modest instability over Lake Michigan is producing an equally modest
shower response that is gradually extending east as shortwave energy
aloft pivots overhead. Deep saturation and lift will continue to
promote showers lifting into areas north of roughly I-69 through the
early morning hours. Subsidence wake will likely cause activity to
retract back closer to the lake for the remainder of the afternoon.
Extensive stratus canopy extending back into the northern Great
Plains is not going anywhere, especially with southwest surface
winds veering to westerly over the lake as the low-level flow
flattens out a bit today. Further, NAM12 forecast soundings indicate
aggressive deepening of the subsidence layer this afternoon into
this evening, but high quality moisture remains in tact below 5kft
well into tonight. Lake enhanced drizzle production overnight will
likely be a consideration for the day shift today. Raised forecast
lows several degrees due to extensive cloud cover and steady
gradient wind.

The energy digging south along the California coast this morning
will cut off over Mexico, opening the door for a weak wave of
Pacific origin to translate along the northern tier on Sunday. Solid
NWP consensus here, so no complaints with likely pops on Sunday.
Ptype will largely depend on timing given marginal temperature
profiles and ongoing warm advection in advance of the wave. Attm,
NWP consensus suggestive of rain in the aftn and mostly snow after
sunset. QPF output of 0.1 to 0.2" is in line with unimpressive 850-
700mb layer specific humidities falling short of 3g/kg. Hard to
envision more than an inch or so of accumulation even if ptype is
all snow. Would expect timing to shift around in the models given
progressive nature of the northern branch and the fact that the
energy of interest is only just making it past the International
Dateline this morning.

Slightly variable temps through the extended as episodes of
progressive shortwave troughing are interrupted by the tendency for
longwave ridging over the Great Lakes due to persistent height falls
out west. No expectation for significant departures from normal with
daytime highs likely remaining +/- 5 degrees of average through day



Extended period of cold cyclonic flow will sustain gusty conditions
today through Friday.  Westerly gusts generally peaking in the 25 to
30 knot range today.  This will maintain small craft conditions for
waves from outer saginaw bay through the tip of thumb.  Winds become
more northwesterly on Friday.  High pressure for the weekend will
allow winds to become light and variable.


Issued at 1150 PM EST Wed Nov 30 2016


Cold air advection through the night will support decent low level
mixing which in turn will sustain some degree of gustiness to the
west-southwest winds through Thurs afternoon. Regional observations
along with recent model guidance suggest the strato cu which moved
into the area this evening will persist through the TAF period.
Ongoing low level moisture advection will support predominately MVFR
type ceilings. This moisture combined with some upper level forcing
and over lake instability will support some rain and snow showers
this morning, primarily over FNT and MBS. The better chances for
showers will then shift south toward metro Detroit on Thurs as winds
over Lake Mi turn more westerly.

For DTW...Observations have shown some improvement in ceiling
heights across northern Indiana, which may nudge into metro at times
this morning. Meanwhile, sub 2k ft cigs have developed just west of
metro, with more widespread lower end MVFR cigs across Wisconsin.
With this additional low level moisture set to move into metro this
morning, there is likely to be a good deal of variability in ceiling
heights, with the overall trend toward sub 2k ft bases.

//DTW Threshold Probabilities...

* High in ceilings below 5000 ft tonight through Thursday.


Lake Huron...Small Craft Advisory until 7 AM EST Friday FOR LHZ421-441.

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



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