Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 192358 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
658 PM CDT Wed Apr 19 2017

.UPDATE...

&&

.AVIATION(00Z TAFS)...

Some MVFR ceilings are possible through the early evening hours,
with VFR ceilings then expected until showers and thunderstorms
move into the area. The main window for the showers and
thunderstorms should be from 03z until 09z Thursday from west to
east across the area. Ceilings and visibilities may drop down to
below alternate minimums in any strong/severe storms, along with a
risk for hail and strong winds.

Some showers and isolated storms may linger until 13z or so in
the east, before moving out of the area. Low ceilings to IFR
category are possible late tonight into Thursday morning, mainly
in the northern portions of the area.

There should be a period of low level wind shear across the area
from around 09z to 13z Thursday, with southwest winds around 40 to
45 knots at 2000 feet above ground level.

Surface winds should gradually veer from east/northeast this
evening to southwest by later tonight into early Thursday morning.
Winds should then veer west behind a cold front later Thursday
morning into the afternoon. Gusts to around 25 knots are expected
in the afternoon.

Wood

&&

.PREV DISCUSSION... (Issued 248 PM CDT Wed Apr 19 2017)

SHORT TERM...
Tonight and Thursday...Forecast Confidence is High.

12Z NAM appears to concentrate a little too much of the
thunderstorms tonight well north, along the 850 mb warm front.
HRRR is similar, though it does have a little more
showers/thunderstorms near the warm front. The GFS has more
showers/thunderstorms after the 850 mb warm front lifts north
this evening, which is preferred. Biggest issue is how quick the
rather deep low level inversion and surface cool air mixes out and
lifts north. Still looks like a severe thunderstorm potential.
Mainly hail later this evening. Low tornado threat near the warm
front just after midnight and early morning, mainly southwest of
Madison. The GFS has around 950 J/kg of mixed layer Cape at 4 am
in south central Wisconsin, with zero to 3 km EHI`s of 1.75.

A wind threat will exist with any morning thunderstorms with the
cold front.

Brisk west to northwest winds are then expected Thursday.
Initially expect a stratocumulus shied to move in behind the cold
front. Southwest areas may scatter out late in the afternoon.

LONG TERM...
Thursday Night through Wednesday...Confidence Medium.

Split flow aloft will keep the most active weather to our north
and south. Will need to continue to monitor the evolution of the
cutoff low across the Midwest, but current indications is for the
to move east with time and remain to our south. Surface high
pressure will dominate our weather regime. Low level flow will
generally be out of the northeast, which should keep temperatures
at/just above average for late April. Upper level ridging builds
across the area late Sunday into Monday and afternoon highs should
return to the 60s for most areas (aside from the typically cooler
conditions near the lake).

The upper level pattern transitions to more of a zonal
orientation, with a few speedy shortwaves sliding through the area
in the Monday Night through Wednesday time frames. Consensus
suggests rain chances for Monday night and again on Wednesday,
with limited thunder potential. Temperatures will remain above
average through midweek. Beyond midweek, a transition to a much
more amplified upper pattern and the potential for even warmer
temperatures.

AVIATION(18Z TAFS)...
MVFR cigs across much of the forecast area. expect an area of
showers and scattered thunderstorms to develop later this
afternoon and evening ahead of an approaching warm front.
As a strong low exits Iowa and reaches central Wisconsin, a cold
front will push through from the west late tonight and during the
morning. Southern Wisconsin will briefly be in the warm sector
before move MVFR cigs spread in behind the cold front.

A few IFR cigs/vsbys in heavier thunderstorms.

MARINE...
As low pressure exits Iowa and strengthens across far southeast
Minnesota and central Wisconsin late tonight, winds will
increase. Winds will veer from northeast to east, to southeast,
ahead of a warm front that will lift north tonight. Winds and
waves may exceed small craft criteria, so will issue one north of
Milwaukee. Thunderstorms are expected tonight with the warm
front, and again with the cold front Thursday morning.

Then strong southwest and west winds expected in the wake of a
passing cold front Thursday with small craft advisory winds across
the near shore region.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory from 3 AM Thursday to 4 AM CDT Friday for
     LMZ645-646.

     Small Craft Advisory from 10 PM this evening to 4 AM CDT Friday
     for LMZ643-644.

&&

$$

Update...Wood
Tonight/Thursday and Aviation/Marine...Hentz
Thursday Night through Wednesday...Gagan



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