Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 271744 AAB
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1244 PM CDT Mon Mar 27 2017

.UPDATE...

Winds are becoming northeast this afternoon. There is a small
chance of light rain or drizzle due to weak lift from mid and
upper level synoptic features, but nothing widespread or
measurable. Rain associated with low pressure tracking through
central IL is expected to remain south of the WI/IL border this
afternoon/evening.

&&

.AVIATION(18Z TAFS)...

Ceilings are on their way up early this afternoon. Expect MVFR
cigs in the 1000-2000 ft range this afternoon. That will probably
continue all night, but there is a chance they could drop back
down to IFR for a while. Light fog will be possible mainly west of
Madison overnight.

Dry air will work its way into southern WI from the north late
Tuesday morning. Expect a trend to VFR cigs and eventual clearing
Tue afternoon/evening.

&&

.PREV DISCUSSION... (Issued 1036 AM CDT Mon Mar 27 2017)

UPDATE...

Light winds will gradually shift to the northeast late this
morning. The visibility is improving everywhere, along with
thinning low clouds. However, as winds become northeast near the
lakeshore, fog and low clouds from the lake are spreading inland.

Gloomy day today. Kept the small chance for light rain or drizzle
in forecast today to account for very weak lift in the upper
levels.

AVIATION(15Z UPDATE)...

Winds are gradually becoming northeast this morning. Once the
winds went NE in Milwaukee, fog and low clouds from the lake
spread into the airport. This will likely impact Kenosha late this
morning as well. These low conditions are expected to improve
early this afternoon, but confidence is low at this time.

MARINE...

Extended the marine dense fog advisory until mid afternoon when
increasing northeast winds should help to diminish the fog.
Northeast winds and waves will approach small craft advisory
levels late tonight into Tuesday, but so far they should stay just
under criteria so no headline.

PREV DISCUSSION... (Issued 304 AM CDT Mon Mar 27 2017)

SHORT TERM...

TODAY and TONIGHT...Forecast confidence is medium.

With light winds and ample low level moisture, expect areas of fog
early this morning. Do not think dense fog is high enough of a
possibility for a dense fog advisory. The baggy surface pressure
gradient will remain over southern Wisconsin through afternoon as
another surface low approaches and winds become northeast. Best
chance for rain will be in southeast WI during the afternoon and
early evening as upper level divergence increases ahead of the upper
shortwave that moves across Illinois later this afternoon.

Forecast soundings show moisture trapped beneath a low level
inversion, so the low clouds will continue.

TUESDAY AND WEDNESDAY...Forecast confidence is medium.

Zonal flow aloft will gradually turn northwest as a ridge builds
into the region. The ridge axis will be over southern Wisconsin by
Wedensday morning, and there is some evidence that a weak shortwave
will move through just behind the ridge axis.

Closer to the surface, strong high pressure will build into southern
Canada, placing southern Wisconsin solidly within anticyclonic flow.
RH fields in the lower levels dry out from north to south on
Tuesday, and should stay dry until moisture begins to build into
the SW on Wednesday afternoon ahead of a developing low pressure
system over the Great Plains. Tuesday afternoon should end up
pretty sunny, but unfortunately an area of high RH in the upper
levels of the atmosphere is progged to move over southern WI on
Wednesday, so it looks like we will have increasing cloudiness on
Wednesday.

GFS/NAM are both hinting at a secondary surge of cold air pushing
south through the state on Tuesday. The signature is pretty messy,
but there is some coherent fgen bands and locally strong CAA
present in both models. Will leave this out of the forecast for
now, but if this does happen, temperatures will obviously need to
be adjusted downward. Additionally,with easterly winds through
the period, lakeside locations will remain cooler than spots
inland.

LONG TERM...

WEDNESDAY NIGHT THROUGH FRIDAY...Forecast confidence is medium.

Differences in model solutions remain, but overall guidance does
seem like it`s beginning to zero in on a consensus. Cutoff low
aloft/low pressure at the surface over the southern plains on
Wednesday will move to the northeast, reaching the eastern Great
Lakes by Friday evening. The GFS forecast, which was previously
tracking the low south of the Ohio river is now much farther north,
more in line with the Euro/Canadian. If anything, the Euro now
appears to be somewhat of an outlier, pushing the system through
the area a bit faster than the GFS/Canadian.

Regardless, precip is likely on Thursday as the warm front extending
from the low moves into the region. Precip could end as early as
midnight on Friday if the Euro is to be believed, and as late as
Friday night as shown by the Canadian. Temperatures will start out
right around freezing on Thursday morning, so those will have to be
watched closely. Given the warm air aloft associated with the warm
front, we may see a wintry mix situation play out on Thursday
morning before switching to rain in the afternoon. If rain does
linger into Friday, another round of wintry precipitation would be
possible in the morning.

SATURDAY THROUGH MONDAY...Forecast confidence is low.

The models bring another northern stream shortwave through the area
on Saturday as another cutoff low develops in the desert southwest.
Surface low pressure will likely develop somewhere in southern
Canada over the weekend, but there is not enough of a consensus to
get a good idea of where that will be, where it will track, and when
it will happen.

AVIATION(06Z TAFS)...

Widespread rain is winding down now in the northeast forecast area
with just a little drizzle to linger into early tonight. Could see
a little light rain brush the southeast tomorrow afternoon, but
otherwise it will be drier tonight into Monday.

Low clouds will persist into Monday. Could see some low
visibilities again tonight into Monday morning given the recent
rainfall and light to calm winds at the surface. Seeing a few
lower observations developing in the southern forecast area, but
nothing widespread thus far. Will continue to keep an eye on the
potential for dense fog into Monday morning.

MARINE...

With low level moisture  and light winds in place, will leave the
end time of the Dense Fog Advisory, although weak northwest winds
will likely keep the thicker fog towards open waters.

Gusty north winds with high pressure centered north of lake
Superior, will likely bring Small Craft Advisory conditions back
into the area late tonight and especially Tuesday and Tuesday
night.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Dense Fog Advisory until 3 PM CDT this afternoon for LMZ643>646.

&&

$$

Update...Cronce
Today/Tonight and Aviation/Marine...Hentz
Tuesday THROUGH Sunday...BSH


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