Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 200528
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1128 PM CST Mon Feb 19 2018

.UPDATE...

A brief break in the heavier rain has developed over the region,
with the steadier precipitation currently across northern
Illinois. Further north, the freezing line has mostly stayed put,
and is currently aligned from Reedsburg to Baraboo to north of
Fond du Lac and Sheboygan. Across this area, just some patchy freezing
drizzle is currently taking place.

An additional push of precipitation is expected overnight,
arriving in the 4 AM to 6 AM timeframe. More widespread freezing
rain will be possible north of the freezing line for at least a
few hours, before the freezing line eventually lifts north after
sunrise.

Over the southern forecast area, this additional rainfall will add
to the ongoing flood issues. While the individual flood reports
have generally been minor thus far, they`ve become quite
widespread across the the Areal Flood Warning area. It appears
that quite a few roads may be impassable across the area by
daybreak.

&&

.AVIATION(06Z TAFS)...

Conditions should generally be IFR or LIFR overnight, as
additional rain moves into the region. Low ceilings and fog will
also continue at the terminals. Some brief breaks from the low
clouds and fog will be possible at Kenosha early in the overnight,
but this is not expected to last, as additional moisture lifts
north.

Marginal improvements are expected Tuesday, though IFR will likely
persist for most of the day. Conditions should improve rapidly
Tuesday evening, as a cold front sweeps across the area.

While no freezing or frozen precipitation is currently forecast
for the TAF sites, light freezing rain and/or freezing drizzle is
expected overnight north of a line from Baraboo to Fond du Lac to
Sheboygan.

&&


MARINE...

Waves will be between 3 and 5 feet north of Port Washington
overnight, and a Small Craft Advisory remains in effect for this
area until 6 AM. Further south, fog will reduce visibility to less
than 1 mile at times, and a marine Dense Fog Advisory is in
effect, also until 6 AM.

&&

PREV DISCUSSION... (Issued 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.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch through Tuesday afternoon for WIZ064>066-068>072.

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

     Winter Weather Advisory until 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 until 6 AM CST Tuesday for LMZ643.

&&

$$

Update...Boxell
Tonight/Tuesday and Aviation/Marine...Boxell
Tuesday Night through Monday...99



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