Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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738
FXUS63 KMKX 250508 AAC
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1208 AM CDT Sat Mar 25 2017

.UPDATE...

.AVIATION(06Z TAFS)...

Showers are beginning to fill in more from the south and will
continue to do so overnight into Saturday morning. Showers will
then hang on through the day most places. Low clouds are expected
through tomorrow. Will probably see some lower visibilities form
as the front creeps back north into northern Illinois later
tonight into Saturday.

&&

.PREV DISCUSSION... (Issued 1027 PM CDT Fri Mar 24 2017)

UPDATE...

Rain continues to be fairly persistent in the far northwest and
far south late this evening. The focus should turn to mainly the
south half overnight, spreading northward Saturday morning. A
rumble or two of thunder is not out of the question toward the
Illinois border tonight into tomorrow morning. Low temps seem to
be on track for tonight.

MARINE...

Left timing of Small Craft Advisory as is for now, though looks
like it could eventually be extended into Sunday morning until the
waves subside below 4 feet.

PREV DISCUSSION... (Issued 720 PM CDT Fri Mar 24 2017)

UPDATE...

Rain will continue to fill in across the area this evening. The
front has dropped into northern IL, bringing an end to the mild
weather. No significant updates are expected this evening into
tonight.

AVIATION(00Z TAFS)...

Showers will fill in this evening and tonight, persisting on and
off through the day Saturday. Ceilings have been dropping from the
north and east as the colder air arrives. Low clouds are expected
to hang around through tomorrow. Will probably see some lower
visibilities form as the front creeps back north into northern
Illinois.

PREV DISCUSSION... (Issued 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 squeak 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. A
lot 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 precipitaion.

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.

&&

$$

Update...DDV
Tonight/Sunday and Aviation/Marine...Cronce
Sunday Night through Saturday...MBK



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