Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 281501 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1001 AM CDT Wed Jun 28 2017

.UPDATE...

A line of showers and a few thunderstorms developed out ahead of
the main area of weakening showers over southeast WI this morning.
These are on the leading edge of the nose of the low level jet.
There are signs of convection developing over northeast Iowa late
this morning. I think this will be the thing to watch for our next
round of thunderstorms in southern WI around mid afternoon. This
will be a long the CAPE gradient and within steady 850mb warm air
advection and moisture transport. The potential for severe is
there, but surface-based CAPE is going to be limited until we get
some sunshine.

There is sunshine over western IA right now, so if we can get that
late this afternoon, then there is potential for severe
thunderstorms this evening. Nevertheless, we can expect yet
another round or two of thunderstorms later this evening. One
round with the outflow boundary from this mid afternoon
convection, and another round with a surface frontal boundary.

&&

.MARINE...

Gusty southerly winds will ramp up late this morning and remain
so through late evening. Waves will build to 3 to 6 feet by this
afternoon. A small craft advisory is in effect


&&

.PREV DISCUSSION... (Issued 524 AM CDT Wed Jun 28 2017)

AVIATION(12Z TAFS)...

Showers and storms will push across the area this morning. They
reach Madison around 8 am and Milwaukee around 11 am. Look for
CIGS to steadily lower, possibly dropping to MVFR levels for a
few hours during the morning rain. Look for VFR conditions then
from this afternoon into tonight. We could see thunderstorms
redevelop late this afternoon and evening, but it is conditional
on how quickly we can clear out the clouds and rain from the
morning activity. There are indications that redevelopment will
occur primarily across Iowa into Illinois and possibly far
southern Wisconsin. If we clear out, much of southern Wisconsin
will be threatened by strong storms. Brief MVFR/IFR CIGS/VSBYS are
possible with any thunderstorms.

Look for breezy southwest winds today, diminishing tonight.

PREV DISCUSSION... (Issued 310 AM CDT Wed Jun 28 2017)

SHORT TERM...

Today and tonight...Forecast confidence is high.

Confidence is high that the area will get some rain and
thunderstorms today. Confidence is more challenged with respect to
the severe potential. The concerns/challenges remain the same as
those expressed in prior discussions. We have a morning round of
showers and storms that will come through with the initial warm
and moist air advection. The morning activity is not expected to
be severe and will be diminishing through the morning in typical
nocturnal thunderstorm fashion. It should reach the Madison area
by mid morning and the Milwaukee metro area by late morning. It
will be falling apart by mid day.

The concern is our ability to recover for the afternoon. The
morning activity will lay out a boundary from southern Wisconsin
back into Iowa that will then be the focus for redevelopment. It
appears the best initiation along this boundary will be across
Iowa this afternoon, where the atmosphere will have the best
chance to recover, also coupled with strong deep layer shear.
Another area of redevelopment will be closer to the low center and
deeper dynamics over west central and northwest Wisconsin.
Southern WI may be fairly dry through the afternoon as we wait for
the upstream redevelopment to move in.

Redevelopment occurs late this afternoon across Iowa. As that
activity organizes into a linear system, it should push into
southwest Wisconsin, possibly connecting with the convection
farther to the north, moving through the remainder of southern
Wisconsin. However, some of the models do show a weakness in
coverage across southern Wisconsin this evening, so we`ll have to
see how this plays out.

SPC has put all of southern WI in a slight risk with an Enhanced
risk now running from Baraboo, to Madison to Janesville and points
west. This is conditional, of course, and depends on where the
morning convective boundary lays out, where the atmosphere
recovers best and how the new development upstream behaves this
afternoon. Large hail, strong winds and a few tornadoes are
possible. The highest tornado threat will be in the enhanced risk
area.

LONG TERM...

Thursday through Saturday...Forecast confidence is medium:

Another low pressure system will approach on Thursday and is
expected to move through Thursday night and Friday. There will be
a chance for showers/storms by later Thursday afternoon and into
the evening as deeper moisture and better instability return.
Showers and storms are then likely Thursday night into Friday as
the low moves through. SPC has the main severe wx threat through
this period to the east on Friday, which makes sense given the
timing of the low passing through earlier in the day.

Scattered showers and a few storms are possible Saturday as a
wave rotates through the broad upper trough in place over the
Great Lakes.

Should see temps within a few degrees of normal Thu-Sat.

Sunday through Tuesday...Forecast confidence is medium:

Have some low precip chances Sunday per the Canadian bringing
another wave through. Looks like a dry day though per the GFS and
ECMWF. Better confidence that a wave may bring showers and storm
chances Monday as a troughing pattern remains in the region.

The flow turns more zonal for Tuesday as the trough departs. The
GFS and Canadian show a waves sliding through with precip clipping
the south, so have some low precip chances in there. The ECMWF
has a stronger surface high that arrives sooner, which would
result in a dry day.

Temps early next week look near normal.

AVIATION(06z TAFS)...

Early morning clouds are increasing ahead of an approaching area
of showers and thunderstorms. LLWS is developing at this time,
but will dissipate by late morning as breezy south winds develop
at the surface. An area of showers and scattered thunderstorms
will move east across southern Wisconsin through the day with
additional development of strong to severe storms late this
afternoon or evening. Areas of MVFR cigs and IFR vsbys will be
likely in showers or thunderstorms.

MARINE...

Strong south to southwest winds will result in small craft
advisory conditions today through tonight.

BEACHES...

Strong southerly winds will bring a high swim risk to the Sheboygan
county beaches.  Winds will be a bit more off shore and waves will
be lower south of that area.  However, a moderate swim risk covers
all of southeast Wisconsin Lake Michigan beaches.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement from 1 PM CDT this afternoon through
     late tonight for WIZ052.

LM...Small Craft Advisory until 6 AM CDT Thursday for LMZ643>646.

&&

$$

Update...Cronce
Today/Tonight and Aviation/Marine...Davis
Thursday THROUGH Tuesday...DDV


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