Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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073
FXUS63 KDTX 011122
AFDDTX

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

.AVIATION...

Cold cyclonic flow now encompassing the region will sustain an
extensive field of stratus through the TAF period.  As noted in
recent satellite and observational trends, there will be periodic
fluctuations in ceiling heights between low VFR and MVFR throughout
the day.  Maintenance of sufficient lapse rates with a diurnal
component will sustain gusty southwest conditions throughout the
daylight period.  Some pockets of light rain and/or snow showers
will continue to funnel downstream.  Trajectory favors FNT/MBS
early, before the focus shifts southward later today as flow veers
more westerly off Lake Michigan.

For DTW...Periodic fluctuations of ceiling heights between low VFR
and MVFR through the day, but with cigs holding firmly below 5000
ft.  Low chance for light rain showers to enter the airspace this
afternoon and evening.

//DTW Threshold Probabilities...

* High in ceilings below 5000 ft through tonight.

&&

.PREV DISCUSSION...
Issued at 312 AM EST Thu Dec 1 2016

DISCUSSION...

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
7.

MARINE...

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.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 4 PM EST Friday FOR LHZ421-441.

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

$$

AVIATION.....MR
DISCUSSION...JVC
MARINE.......MR


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