Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 192131
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
331 PM CST Mon Feb 19 2018

.SHORT TERM...

Tonight And Tuesday...Forecast Confidence Is High.

The details and reasoning of the forecast continue to tighten up.

The biggest challenge has been locking in the expected surface
temps in the region hovering near or just below freezing northwest
of Milwaukee and Madison. Then the total precipitation amounts
across the area.

Fortunately, those precip amounts have dropped considerably
across Columbia, Sauk, Marquette, Green Lake and Fond du Lac
counties. That allowed us to downgrade the Ice Storm Warning to a
Winter Weather Advisory. Colder temperatures are pushing out of
the northeast and into Sheboygan and Fond du Lac counties as the
northeast gradient flow increases. Sheboygan county needs to be
watched closely, as temps could start to fall quicker than
expected there. Roads should still become quite hazardous
overnight into Tuesday morning, but the potential damage to power
lines, etc has diminished considerably.

We`ll see rain move through this afternoon and early evening,
with a diminishing trend for a while, then another surge of rain
pushes in later tonight into Tuesday morning. This is a result of
the fluctuating low level jet.

The focus for the heaviest rainfall remains across the far
southeast, south into Illinois. We`re still looking at totals in
the 1 1/2 to 2 inch range over southern Milwaukee, Racine,
Kenosha, Walworth and Rock counties.

Additionally, a few thunderstorms may occur tonight into early
Tuesday and this focused heavy rainfall could result in some
flooding.

Dense fog will be a problem for far southern WI overnight due to
light winds, very moist conditions and an existing snowpack. It
may lift from time to time as rain moves through. It will be more
of a problem in rural areas vs urban.

We finally see a diminishing trend from west to east on Tuesday
with most areas drying out during the evening on Tuesday.

Tuesday Night Through Thursday...Forecast Confidence Is Medium.

Any lingering precipitation is expected to wind down Tuesday
evening from northwest to southeast across the area. There is some
potential for light freezing rain or drizzle to occur during this
time, as drier air mixes out ice crystals. However, upward
vertical motion will be weakening, so not sure if this will even
materialize.

Strong cold air advection continues Tuesday night into Wednesday,
as high pressure moves eastward toward Wisconsin. The high will
then shift east across the region Wednesday night and Thursday.
Quiet weather is expected Wednesday into Thursday morning, with
temperatures a little below seasonal normals.

The dry easterly flow in the low levels Thursday afternoon will
probably hold off the next system until Thursday night. The
current low PoPs in areas west of the Dells to Janesville may be
removed in later forecasts. Temperatures should climb back to near
or a little above normal on Thursday.

.LONG TERM...

Thursday Night Through Monday...Forecast Confidence Is Medium.

Models have the next system moving east through the region
Thursday night into Friday. There is modest upward vertical motion
with this system, with modest warm air advection. The low level
jet nose is pointing into central and northern Wisconsin, though
there is a decent feed of moisture in the low to middle levels.
GFS forecast soundings are showing potential for some freezing
rain to occur, with a lack of ice crystals in the air column. For
now, will just mention snow Thursday night with a change over to
rain Friday. This may need to be watched for impacts for the
Friday morning commute.

Models then have low pressure moving northeast from the southern
Plains to the eastern Great Lakes region Saturday into Sunday.
There is some variation with the track, but each does give the
area some precipitation mainly Saturday night into Sunday morning.
Kept blended PoPs going for now. This could bring some snow to the
area Saturday night. Temperatures look mild later in the week and
over the weekend. How these temperatures impact precipitation
types will be interesting to see.

&&

.AVIATION(21Z TAFS)...

Expect the rain showers to become more numerous across the area
into this evening, with rain then expected tonight into Tuesday.
Freezing rain is expected to develop mainly from the Dells to Fond
du Lac and north this evening, lingering into Tuesday morning.
Ice accumulations up to 1/4 inch are forecast in these areas.

The southeast portions of the area are most at risk for heavy
rainfall from embedded thunderstorms tonight into Tuesday, with 1
to 1 1/2 inches of rain possible. Runoff may lead to some
flooding or standing water on runways. Kenosha would be the most
susceptible, with Milwaukee and Waukesha having a somewhat lower
risk.

Ceilings should be mainly around 300 to 500 feet into Tuesday,
and may get lower at times with heavy rainfall. Visibility values
should get to around 1/2 to 1/4 mile with dense fog at times in
the southern portions of the area into tonight. Values will be a
bit higher to the north and in any heavier rain bands. 1/2 to 1
mile visibility values may linger Tuesday morning, before
improving from west to east later in the day.

Winds will generally be light. Low level wind shear is expected
at times overnight into Tuesday at Kenosha, and mainly Tuesday at
Milwaukee and Waukesha. Southwest winds around 35 to 45 knots are
expected around 2000 feet.

&&

.MARINE...

Small Craft Advisory remains in effect from 6 PM CST this evening
until 6 AM CST Tuesday morning for areas north of Port Washington.
Northeast winds of 10 to 20 knots are expected during this time,
before weakening Tuesday morning. This will bring building waves
of 3 to 5 feet this evening, lingering overnight before subsiding
by 6 AM CST Tuesday morning.

Dense Fog Advisory continues south of there into tonight, with
light winds and saturated low levels. This may linger into
Tuesday morning, before improving during the afternoon.

&&

.HYDROLOGY...

The heavy rainfall expected in the southeast parts of the area
tonight into Tuesday may lead to excessive runoff and localized
flooding, as well as some rivers rising above flood stage. Will
continue to monitor area river gauges, as well as low lying areas
for flooding potential.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch from 6 PM CST this evening through Tuesday afternoon
     for WIZ064>066-068>072.

     Dense Fog Advisory until 6 AM CST Tuesday for WIZ062>072.

     Winter Weather Advisory from 6 PM this evening to 3 PM CST
     Tuesday for WIZ046-047-051-052-056>058.

LM...Dense Fog Advisory until 6 AM CST Tuesday for LMZ644>646.

     Small Craft Advisory from 6 PM this evening to 6 AM CST Tuesday
     for LMZ643.

&&

$$

Tonight/Tuesday...Davis
Tuesday Night through Monday and Aviation/Marine...Wood



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