Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 191759 AAB
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1159 AM CST Mon Feb 19 2018

.UPDATE...

We dropped the Ice Storm Warning for the northern and northwestern
counties, and replaced it with a Winter Weather Advisory for
freezing rain. We are still expecting freezing rain to occur in
the advisory area, just not as much as in previous forecasts.
There will still be impacts to travel, with icy roads expected for
the Tuesday morning commute, so make sure to prepare for this.

We also removed Dane County from the Flood Watch, as it looks like
the main impact from any potential heavy rainfall and flooding
will be to the south and east of there.

&&

.AVIATION(18Z TAFS)...

Expect the spotty rain showers to become more numerous across the
area this afternoon, with rain 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 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 mile with the rain. If the rain becomes
lighter or lets up at times into Tuesday, dense fog down to 1/4
mile or less is possible.

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.

&&

.PREV DISCUSSION... (Issued 1007 AM CST Mon Feb 19 2018)

UPDATE...

12Z NAM and GFS have come in with lower QPF across northern and
western portions of the area for this afternoon into Tuesday.
Mesoscale models are also showing this trend, and it was also
keeping simulated reflectivity more scattered to numerous this
afternoon. These models then bring more solid rain into the far
southeast counties tonight into Tuesday, with some convection.

This may be due to the fact that there is a lack of a significant
shortwave trough with this system for tonight and Tuesday, and
that the upper divergence looks to remain more to the south of the
area. However, there is still impressive low level frontogenesis
response and low level jet nose convergence pushing through the
area this afternoon and tonight, with the frontogenesis response
lingering into Tuesday, focused on far southeast Wisconsin. Thus,
the heavy rainfall in the southeast still looks on track, and
potential runoff and areal/river flooding there remains a concern.

There may not be as much QPF and ice accumulation in the north
and west as previously thought through Tuesday, though there will
still be some freezing rain there. We are evaluating these trends,
and may end up having to change some of the winter weather
headlines that are currently out there. We will try to have some
changes ready in the next hour or so.

MARINE...

Small Craft Advisory remains in effect from 6 PM CST this evening
until 6 AM CST Tuesday morning. 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.

HYDROLOGY...

Flood Watch continues across areas around and south of the Madison
and Milwaukee metro areas from 6 PM this evening until 6 AM
Wednesday morning. As stated in the updated section above, areal
and river flooding remains a concern in this area, due to heavy
rainfall and potential runoff/snow melt.

There are a handful of rivers that may reach minor to possibly
moderate flood stage in these areas, with the largest rises at the
Sugar River at Brodhead and the Fox River at New Munster. Will
keep the Flood Watch going for now.

PREV DISCUSSION... (Issued 544 AM CST Mon Feb 19 2018)

UPDATE...The surge of moisture and developing areas of rain is
approaching from IA and IL for later this morning. The forecast is
on track for today and Tue.

AVIATION(12Z TAFS)...A surge of moisture will arrive later this
morning bringing stratus under 1 kft and reduced vsbys of 1-3SM
via light fog. The surge of moisture will also bring rain with
possibly embedded tstorms. The low cigs and areas of fog will
then continue through tnt-Tue along with the rain and embedded
tstorms. Freezing rain will occur toward central WI at times from
this afternoon through Tue. LLWS will occur at times in se WI
tonight through Tue AM.

PREV DISCUSSION... (Issued 428 AM CST Mon Feb 19 2018)

SHORT TERM...

Today through Tuesday...Forecast Confidence is Medium...

A band of moderate to sometimes heavy rainfall still looks fairly
certain over se WI where forecast rainfall totals are still from
1.50-2.00 inches. This is due to a nose of a strong LLJ
intersecting a stationary front, thus producing impressive
frontogenesis and lift from the sfc-700 mb. Isolated to scattered
tstorms will occur at times given marginal elevated Cape and PWs
slightly over one inch. The Flood Watch looks good with quick
rises on creeks and small rivers possible along with the potential
for flooding in the typical low lying areas.

There is some uncertainty with the winter wx portion of the storm.
There may be a fairly sharp gradient in rainfall totals resulting
in less icing toward central WI. Sfc temp forecasts have also
trended warmer reducing the amount of icing. Therefore, shifted
the icing threat north but still with an Ice Storm Warning for
Sauk, Columbia, Marquette, Green Lake and Fond du Lac Counties. A
Winter Wx Advisory for Dodge and Sheboygan Counties.

LONG TERM...

Tuesday night... Forecast confidence is Medium.

As precip ends from northwest to southeast Tuesday night, there is
a chance that the rain will turn to freezing rain for a couple
hours as the surface temps drop before the dry air arrives. This
would only be a light glaze, if any.

The bigger problem will be the "flash freeze" Tuesday night. Any
standing water will freeze quickly as temps drop into the teens
and lower 20s. The hope is that the steady northerly wind will
allow roads to dry quickly enough so they don`t become icy.

Wednesday through Saturday... Forecast confidence is Medium.

Precip is no longer expected on Wednesday into Wednesday night.
Instead, the next chance for precip will be Thu afternoon or night
as we get into another warm air advection, vorticity advection,
upper divergence scenario. The ECMWF brings that forcing through
quickly and dries us out by Fri afternoon. The GFS gives us
several rounds of light precip all the way through Sat morning.
Precip type would begin as snow Thu nt into Fri morning, then
transition to rain Fri and back to light snow Fri night into Sat
morning.

Saturday night through Monday... Forecast confidence is Medium.

The next round of rain and snow will arrive Saturday night and end
Sunday with a more pronounced shortwave trough.

AVIATION(09Z TAFS)...A surge of moisture will arrive later this
morning bringing stratus under 1 kft and reduced vsbys of 1-3SM
via light fog. The low cigs and areas of fog will then continue
through tnt-Tue. LLWS will occur at times in se WI tonight through
Tue AM.

MARINE...Winds and waves will continue to weaken through this
morning. But brisk northeast winds are then expected to develop
north of Port Washington for tnt with waves building to 3 to 5
feet. A Small Craft Advisory has been issued for this area for tnt
only.

&&

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

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

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

&&

$$

Update...Wood
Today/Tonight and Aviation/Marine...Gehring
Tuesday THROUGH Sunday...Cronce



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