Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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438
FXUS63 KMKX 162133
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
330 PM CST MON JAN 16 2017

.TONIGHT AND TUESDAY - Forecast Confidence...Medium.

Closed upper low will devolve to an open-wave trough while lifting
out of the lower Missouri valley this afternoon and emerging near
Lake Erie on Tuesday. A northern stream shortwave trough, trailing
the upper low, will progress from the northern Great Plains this
afternoon to the western Great Lakes on Tuesday. Synoptic forcing
associated with these waves will keep precipitation chances going
into Tuesday morning.

Our primary concern during this period is with freezing rain chances
into tonight. On a positive note, warm air pushing in from the south
has brought air temperatures across much of the forecast area to
near or above freezing. Road conditions have improved as a result in
both the Milwaukee area and for communities along the Illinois
border. Conditions should gradually improve in the Dodgeville,
Madison, and Jefferson areas as pavement temperatures warm this
afternoon and evening. Temperatures in our far northwest have
struggled to reach freezing, and pavement temperatures will likely
take a while to warm. As such, light icing remains a concern in
these areas (roughly including the communities of Baraboo, Portage,
Montello, and Green Lake). Will keep the Winter Weather Advisory for
our north going for now, with the option for later shifts to cancel
early once the threat of additional freezing rain/light icing has
ended. Keep in mind that some surfaces may still be slippery from
residual icing even in areas where the Winter Weather Advisory has
ended. Precipitation, mainly in the form of rain, will end from west
to east on Tuesday. Areas of fog should develop later tonight given
light winds and a saturated lower boundary layer. Locally dense fog
is possible, especially along the southern Lakeshore.

.TUESDAY NIGHT THROUGH THURSDAY - Forecast Confidence...Medium to
High.

Will keep a small chance for light rain lingering in the evening
over the southeast CWA as upper level short wave and lingering
mid-level deformation exits the area during the evening.

Otherwise a quiet period can be expected Wednesday and
Thursday as southern WI remains in a weakly confluent upper air
pattern.  Cutoff low pressure aloft will remain over the central and
southern Plains while sprawling high pressure will cover much of the
central CONUS on Wed and spread east into eastern CONUS on Thu.
Precipitation from srn Plains low pressure may reach srn Great Lakes
by late Thu as it gets nudged northward.  Expecting drier southwest
flow to erode deeper rh over the area Tue night so that at least
partial sunshine can be expected both Wed and Thu.  With the lack of
any significant cold air intrusion from current system affecting the
region, sunshine, lack of significant snow cover and warmer 925H
temps should contribute to above normal daytime temperatures
reaching the 40s most areas.

.EXTENDED PERIOD...

THURSDAY NIGHT THROUGH MONDAY - Forecast Confidence...Medium.

Medium range guidance in good agreement on several strong higher
amplitude trofs moving across the eastern Pacific into the western
and central CONUS during this period.  First western wave will move
across the west on Thursday and Thursday night.  This will cause the
cutoff upper low over southern Plains to pivot northward on Friday
and Friday night possibly bringing light precpitation to the area.

Increased troffing across the western CONUS will service to keep
milder air in place across Wisconsin and the region through the
weekend.  Hence most of the precipitation expected during this
period will be liquid as temperatures remain above normal for mid-
January.

A second stronger short wave that will be located in the southern
Plains later in the weekend will also get ejected north-northeast
into the central MN and TN valley regions early next week. This
would bring mainly rain back to the area Sunday night into Monday.

&&

.AVIATION/00Z TAFS/...

Precipitation transitioning to all rain for most areas into this
evening. The exception is northwest of Madison, where light freezing
rain may persist into early tonight. Ceilings and visibilities
should drop from IFR to below alternate minimums this evening and
will likely remain there into Tuesday morning before improving.
Areas of fog are expected. The fog may be locally dense, especially
along the southern Lakeshore during times of lighter precipitation.

&&

.MARINE...

Easterly winds will continue to increase for a time this evening as
low pressure near Kansas City tracks northeast toward southern Lake
MI.  After midnight, the winds will subside as the low pressure
center passes in close proximity. The lighter winds and high
humidity will result in areas of dense fog to develop overnight,
especially over the southern marine zones. Hence posted a Dense Fog
Advisory through 9 am CST Tuesday. Westerly winds on the backside of
the low will thin the fog Tuesday morning. Winds ahead of and behind
this low pressure system are now looking to remain below Small Craft
Advisory levels.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...

WI...WINTER WEATHER ADVISORY until 6 AM CST Tuesday for WIZ046-047-
     051-052-056>060.

     WINTER WEATHER ADVISORY until 6 PM CST this evening for
     WIZ062>064.

LM...DENSE FOG ADVISORY until 9 AM CST Tuesday for LMZ644>646.

$$
TONIGHT AND TUESDAY/AVIATION...SPM
TUESDAY NIGHT THROUGH MONDAY/MARINE...MBK



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