Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 230006
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
606 PM CST Sun Jan 22 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 236 PM CST Sun Jan 22 2017

The last of the dense fog should end across Door County by 3 pm as
a weak boundary moves across northeast Wisconsin. Will let the
dense fog advisory expire at 3 pm. The airmass remained moist and
mild with temperatures and dewpoints in the 30s to around 40 as of
mid afternoon.

For tonight, widespread fog is expected later this evening into
early Monday morning. Weak cold advection at 850mb and northwest
winds would not tend to favor dense fog. However, light winds
combined with the mild and moist airmass would support dense fog.
Think areas of dense fog should develop later this evening into
the overnight hours. Due to the uncertainty on how widespread the
dense fog will become, held off on issuing a dense fog advisory
at this time. Some drizzle is possible at time for the remainder
of the afternoon into Monday. Air and pavement temperatures across
northern Wisconsin will hover around 32 degrees late tonight, thus
the fog or drizzle could put a thin coating of ice on area roads.
Another mild day with highs in the middle 30s to lower 40s.

.LONG TERM...Monday Night Through Sunday
Issued at 236 PM CST Sun Jan 22 2017

Main focus in the long term will be the system expected to move
across the area Tuesday and Wednesday.

Monday night and Tuesday morning remain dry, with the exception of
a little leftover rain or drizzle possible in northern Door
County. While a ridge moves across the area during this time, not
expecting much clearing during this period with model soundings
still showing residual moisture at low levels. Nudged lows
Tuesday morning up slightly to account for this, which also seemed
reasonable given that guidance has been trending too cool with low
temperatures.

Models still show differences on the system moving through later
Tuesday and Wednesday. However, gaining some confidence on a
mainly snow event with the heaviest snow in the late Tuesday
evening/early Wednesday time frame. The exact track still remains
questionable which would alter forecast snow amounts. The ECMWF
is the most consistent and a middle of the road approach. The
Canadian and NAM keep the low further south, but these models have
been trending north. The one to watch may be the GFS which now
brings the low the furthest north and would allow for more rain in
the southern counties. Temperatures aloft still support snow
development, so will use boundary layer temperatures as the best
cutoff between rain and snow. Initially may see some rain Tuesday
afternoon, but as temperatures cool Tuesday evening would expect
to change over to all snow. As far as snowfall amounts, once again
opted to follow something closer to ECMWF for QPF amounts, which
brings roughly 3 to 5 inches to most the area, the exception being
the far north. However, this could still change given a more
northern track. These snowfall totals seems reasonable for now
given the differences. As surface temperatures warm above freezing
Wednesday afternoon, would expect to see any remaining
precipitation to end as more of a drizzle or light rain/snow mix.
However, these details still depend greatly on the exact system
track and timing.

For the rest of the forecast period continued with lake effect
snow showers in far north central Wisconsin given the northwest
winds. A couple shortwaves look like they may rotate through the
main flow which could bring occasional snow showers to the rest of
the area late in the week and into the weekend, but nothing of
great significance at the moment. Temperatures trend closer to
normal by Friday and look to stay there through the weekend.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 601 PM CST Sun Jan 22 2017

Areas of dense fog expected again tonight with LIFR conditions as
moisture remains trapped in low-levels of the atmosphere.
Improvement expected Monday, but IFR conditions expected through
much of the morning. CIGS and VSBY improve a little into the
afternoon.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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


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