Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 202030
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
330 PM CDT Tue Jun 20 2017

.DISCUSSION...

.Tonight and Wednesday...Forecast Confidence Is Medium.

Passing shortwave trough in the 700 mb to 500 mb layer combining
with 850 mb to 700 mb frontogenesis response fields will continue
to push the current area of showers and isolated storms in the
southeast counties out of the area over the next hour or two.
There may be a few showers or a thunderstorm that sneak into far
northeastern potions of the area late this afternoon. Think most
of that activity should remain just north of the area.

High pressure passing through the area tonight will bring quiet
weather and gradually clearing skies. Some light fog may form
later tonight, with radiational cooling conditions setting up.
Lows should drop into the lower to middle 50s.

Most of Wednesday looks dry, as the high slides to the east
southeast of the area. Low level jet tries to point into southwest
Wisconsin later in the day, with some synoptic models bringing
light QPF in the western portions of the area by 00Z Thursday.
Mesoscale models are relatively dry in this area Wednesday
afternoon. Forecast soundings are mixed with moisture and show
little elevated CAPE.

For now, added small PoPs for showers in the far west and
northwest areas. Clouds moving into the area in the afternoon may
limit highs from current forecast values in the middle to upper
70s.

.Wednesday night through Thursday night...Forecast confidence is
medium.

This will be a very active period with plenty of uncertainty as to
how the complex evolution will play out. As low pressure
approaches the area Wednesday night, the low level jet intensifies
into the western Great Lakes across an advancing warm front. We
get into deep warm and moist air advection across the boundary
bringing the likelihood of elevated thunderstorms. We are in a
marginal risk for severe storms with that.

That wave of WAA will move off by sunrise on Thursday, bringing a
break in the action during the morning and possibly into the early
afternoon on Thursday. But, a front will get hung up along the
WI/IL border region and should be the focus for repeated rounds of
showers and storms later Thursday afternoon into Thursday night.
It is this second round of the evolution that is most subject to
change. If we get strong enough convection Wednesday night, it may
shove the effective boundary farther to the south, keeping the
next round of storms down in Illinois. This is the Canadian model
scenario. However, the ECMWF/GFS/NAM all have the precip focus
across southern Wisconsin and that could result in some places
getting an inch or two of rain. SPC has southern Wisconsin in a
slight risk of severe for that period. With the front in the area,
we should have a decent amount of shear. However, CAPE may be a
challenge with all the clouds expected.

.Friday...Forecast confidence is medium.

All the action pushes south, so we should get into dry conditions
for Friday and Friday night under high pressure.

.Saturday through Monday...Forecast confidence is medium.

We stay in an active pattern, with lots of uncertainty entering
the picture. The fast zonal flow early in the weekend morphs into
a large digging mid level trough over the Great Lakes by early
next week. A series of weak waves moving through will bring on and
off chances of showers and thunderstorms. Nothing looks
significant at this point, but it will keep temps on the cool side
until further notice.

&&

.AVIATION(18Z TAFS)...

Area of showers and isolated thunderstorms will move east
southeast of the Kenosha area in the next hour or two. Conditions
should remain VFR category during this time. Could see brief 2
mile visibilities in any heavier showers or storms, along with
gusty winds to 20 knots.

Skies should gradually clear out this evening. Light winds
overnight with clear skies may lead to light fog between 09Z and
13Z Wednesday morning. Light northeast to east winds Wednesday
morning will become southeast Wednesday afternoon.

&&

.MARINE...

Area of showers with isolated storms will move to the southeast
of the area over the next few hours. Gusty north northeast winds
and building waves toward Kenosha and south should weaken by
evening.

Gusty southwest to west winds may develop Thursday, and approach
Small Craft Advisory levels. Waves will remain highest over the
open waters.

Showers and thunderstorms are likely Wednesday night into
Thursday, with strong to severe storms possible later Wednesday
night into Thursday.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

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


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