Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 242032
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
330 PM CDT FRI MAR 24 2017

.TONIGHT AND SATURDAY - Forecast Confidence...Medium.

The surface cold front will remain to the south of the IL border
(after it gets there early this evening) through the weekend. This
will keep southern WI in a cool, wet pattern. Look for brisk
easterly winds and periods of rain tonight and Saturday.

Overall, we will be on the stable side of the front. There is very
weak instability at times, so kept a small chance for some thunder
over southeast WI for later tonight as the upper low approaches the
mid Mississippi River Valley. This is the time the low level jet
points into northern IL, so we will be on the northern fringe of
thunder chances.

Southeast WI will see higher amounts of rain than areas toward
central WI tonight into Saturday, ranging from around a half inch
north to up to an inch southeast. Rivers are forecast to rise, with
a few reaching bankfull stage, but so far we are not forecasting
rivers to reach flood stage this weekend.

.SATURDAY NIGHT THROUGH MONDAY - Forecast Confidence...Medium to
High.

Low pressure system continues to undergo occlusion process to the
south of Wisconsin as it drifts northeast.  Sfc low as well as upper
circulation eventually drift across southern WI on Sunday. With deep
moisture in place /column PWAT around 1 inch/ and nearness of weak
low to mid level convergence, thinking higher pops and occasional
light rain and drizzle Saturday night and Sunday.  Decreasing
boundary layer winds as low pressure drifts by wl likely result in
patchy fog.

Cloudy, rainy and cool easterly breezes will keep temperatures down,
especially by the lake.  However some southern locations may break
into the low to mid 50s on Sunday as the low pressure center drifts
across southern WI.  Cloud cover will likely hang on through Monday
but temperatures may be able to squeek back up into the low 50s most
areas.

.EXTENDED PERIOD...

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

Medium range guidance also trending farther south with second short
wave trof moving across central MS Valley region Monday into Monday
night.  This second system also weakens as it moves to the south of
WI as well as stronger, more zonal flow lingering over the Great
Lakes.  For now, wl continue chance pops into Monday night.

Otherwise, upstream longwave trof over western Conus changes into
cutoff low pressure over southwest early in the week.  While this
system sits and spins in the southwest, this allows large area of
subsidence and high pressure passing across southern Canada to have
an effect on the Upper Midwest/Great Lakes resulting in a period of
dry weather mid-week.  Eventually the southwest cut-off low gets
nudged ENE by yet another system pushing onto the west coast. Alot
of differences regarding the track and timing of this system for
later next week.  ECWMF remains most progressive and wetter for our
area with rain returning on Thu.  GFS and Canadian show more zonal
flow  persisting over the Great Lakes causing this system to remain
mostly south of the area.  For now WPC blend favoring more north
ECMWF solution so wl continue chance pops for -ra Thu/Fri. This
shift to a northeast track does make sense as upstream Pacific short
wave follows similar path into southwest CONUS late in the week.

Thermal structure continues to favor all liquid precipitaton.

&&

.AVIATION (18Z TAFS)...

IFR ceilings will settle into southern WI by this evening in the
wake of a cold front that is sagging south this afternoon. Any winds
there are south will shift to the northeast by late afternoon.
Expect easterly winds to be fairly breezy overnight through Saturday
as low pressure tracks across central Illinois.  Look for periods of
rain and fog to bring visibility down to 1 mile at times.

&&

.MARINE...

Adjusted the start time of the small craft advisory to begin this
afternoon since northeast winds are accelerating down the lakeshore
quickly in the wake of a cold front. Expect brisk east winds to
persist through Saturday evening, with waves subsiding later
Saturday night.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...

WI...None.
LM...Small Craft Advisory until 3 AM CDT Sunday for LMZ643>646.

$$
TONIGHT AND SATURDAY/AVIATION/MARINE...MRC
SATURDAY NIGHT THROUGH FRIDAY...MBK


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