Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 220312

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
912 PM CST Sat Jan 21 2017

.UPDATE...Will expand Dense Fog advisory to include rest of south
central and southeast Wisconsin. Expect visibilities to gradually
decrease overnight as boundary layer winds decrease and mild,
moist air lingers over cold surface temperatures. Will have DFA in
southeast WI go into effect at midnight as visibilities currently
3 to 6 miles most locations.

Farther west, visibilities in several locations have already
dropped to one quarter mile or less. If clearing across northeast
IA does make it into parts of southern WI, this would favor
further development of widespread dense fog.


.AVIATION/06Z TAFS/...Back edge of stratus has been making some
northeast progress toward southwest WI this evening. However
latest 11-3.9 micron imagery showing clearing beginning to slow
down around KCID and KALO. With diminishing boundary layer winds,


.MARINE...Expect areas of dense fog to redevelop across the near
shore waters overnight as mild, moist air continues to drift
across the colder lake waters. Hence expanded ongoing Dense Fog
Advisory to include all four marine zones, and extended through
Sunday morning.


.PREV DISCUSSION... /Issued 315 PM CST Sat Jan 21 2017/


TONIGHT - Confidence...Medium
Water vapor shows negatively tilted mid level wave riding northeast
with shra activity confined to areas mainly east and northeast of
the circulation. Surface low vcnty ec MN has lifted warm front into
srn WI so many areas seeing improved vsbys esp across the srn
counties. Gradient proggd to remain baggy however so expect more
dense fog to redevelop in areas that had the daytime improvement.
May need to expand Dense Fog Advisory back into se WI should trends
warrant on evening shift but for now left current headline where it

SUNDAY - Confidence...Medium
A surface low is proggd to shift from the mid Miss Vly into the OH
Vly. The precipitation shield in the nw quad of the low is expected
to remain se of WI. However the surface pressure gradient is
expected to tighten up a bit and this will result in an increased
northerly wind component and cooler though still above normal
temperatures. Any morning fog likely to hang until the northerly
winds can mix things up a bit.

Sunday Night and Monday...Forecast confidence is medium.

A strong shortwave from the Ohio Valley to the southeast U.S.
moves to the east as a large trough moves into the Western U.S.

A strong surface low will track across Kentucky to the mid
Atlantic states with the northern precipitation shield extending
just to our east.


Tuesday and Wednesday...Forecast confidence is medium.

The western U.S. trough pushes into the Plains Tuesday with an
upper level low across southern Wisconsin Wednesday morning.

The ECMWF has trended north toward the GFS track, but is a slower.
The precipitation from this next system is expected to arrive
Tuesday afternoon on the GFS, with the 12Z ECMWF a little slower.

Precipitation will begin as rain or a rain/snow mix most areas,
with some snow potential in areas mainly north of Madison and
Port Washington. The precipitation will change over to a rain/snow
mix or mainly snow later Tuesday night and persist through
Wednesday. Light snow could continue through Wed night. Boundary
layer temperatures will dictate the precip type.

Models are showing a decent amount of qpf, especially the GFS
between 0.25 and 0.50 inch. Because of the mild temperatures, not
expecting much snow accumulation, but 1 to 2 inches toward central
WI is not out of the question.

Thursday through Friday...Forecast confidence is medium.

The upper trough lingers across the Upper Midwest.

Cooler cyclonic flow will continue.  This will keep clouds in
place and the chance for light snow showers or flurries across
southern WI.

Saturday...Forecast confidence is medium.

The upper trough moves off to the eastern Great Lakes with a
northwest upper flow across southern Wisconsin. We will continue
to be in a rather cold northwest flow in the lower levels.

Some breaks have worked into the far southeast resulting in cigs
jumping to MVFR levels. Much of the rest of the area will likely
remain in LIFR or VLIFR conditions both ceiling and visibility-wise.
Even the southeast where improvement has occurred will be vulnerable
to being socked back in tonight as overall flow pattern remains weak
with ample low level moisture. Things should collectively improve
Sunday once srn WI gets in on the gradient of passing low to our
south. This should kick in the north winds helping to dry things out.

Dense fog advisory will remain in effect through at least midnight
for the northern two cuts as areas south of warm frontal boundary
mixed things out. Satellite trends show the northward retreat in the
fog bank quite well. May see some redevelopment as the night wears
on into Sunday morning.


WI...DENSE FOG ADVISORY until noon CST Sunday for WIZ046-047-051-052-

     DENSE FOG ADVISORY until noon CST Sunday for WIZ064>066-069>072.

LM...DENSE FOG ADVISORY until noon CST Sunday for LMZ643>646.



Sunday NIGHT THROUGH Saturday...Hentz is the U.S. government's official web portal to all federal, state and local government web resources and services.