Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 220336
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
936 PM CST Sat Jan 21 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Sunday
Issued at 251 PM CST Sat Jan 21 2017

Webcams and surface observations indicated that widespread dense
fog continued across much of the area this afternoon, except
across Lincoln, Oneida and Vilas Counties. Rain was mixing up the
atmosphere in this region, thus visibilities varied between a half
mile and a few miles.

A moist and mild air mass will remain across the region through
the period. The result, dense fog will continue for most of the
period from the remainder of this afternoon into Sunday morning.
For Lincoln, Oneida and Vilas counties, the fog should become
widespread dense across this region once the rain exits later this
afternoon. Drizzle is still possible at times tonight into Sunday
morning.

A slow improvement in visibilities is expected Sunday morning
with continued improving conditions expected Sunday afternoon
as somewhat drier air works into the region. It will remain mild
with highs mainly in the 30s to around 40. Did lower high
temperatures a few degrees based on the diurnal ranges of the
last few days.

.LONG TERM...Sunday Night Through Saturday
Issued at 251 PM CST Sat Jan 21 2017

Continued low level moisture early in the period, temperature
trends, and the resulting precipitation types with a midweek
system are the main forecast concerns for this portion of the
forecast.

On Sunday night and Monday we continue to see saturation at low
levels, however with a change in wind direction to the northwest
and slightly drier surface dew points advecting into the area
would potentially see some improvement in the persistent fog. As
the snow pack continues to erode away that may also lessen the
dense fog potential. Kept mention of patchy fog through Monday
morning for now.

For Monday afternoon and night models have backed away with the
influence of an inverted trough in lower Michigan. Latest model
blend PoPs shift east leaving a chance PoPs in east and northeast
Wisconsin through Monday night. Would expect any precip to be
mainly rain as air and road temperatures will be above freezing at
this time. Any freezing rain/drizzle looks minimal but would not
rule out some slippery spots if any precip carries through late
Monday night.

Not gaining much more confidence with the timing and track of the
system expected to move through Wisconsin Tuesday and Wednesday,
making the temperatures and precip types tough to resolve. Upper
levels seem to support snow in the area through most of this event,
with the best potential for rain or a mix at the start and end.
Lowered surface temperatures a bit below guidance during this
period to reflect mainly snow Tuesday night and Wednesday morning.
Will need adjust forecast accordingly in the coming periods.

After this system passes the potential for lake effect snow
showers in north central Wisconsin remains reasonable. Continued
northwest winds keep the chance of snow through the remainder of
this period.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 936 PM CST Sat Jan 21 2017

Little change from previous forecast reasoning. Moisture remains
trapped in low levels thanks to melting snow and pre-moistened
atmosphere. As a result, dense fog will linger across much of the
region through Sunday morning.

Patchy fog could linger into the afternoon but overall, conditions
should be improved over the morning hours.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon CST Sunday for WIZ005-010>013-
018>022-030-031-035>040-045-048>050-073-074.
&&

$$

SHORT TERM.....Eckberg
LONG TERM......KLB
AVIATION.......JKL



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