Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 142036
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
336 PM CDT Fri Jul 14 2017

.SHORT TERM...

Tonight and Saturday...Forecast Confidence is High.

These low clouds are finally breaking up and will gradually clear
later this evening as we lose daytime heating and some drier air
aloft reaches us. Radiational cooling and dewpoints sticking
around the upper 50s should allow for some patchy fog to develop
tonight as the surface high tracks over southern WI. The better
chance for fog is over south central WI.

I can`t rule out early morning lakeshore fog because dewpoints
are right around the water temperature, but not enough confidence
to put in the forecast at this time.

We should be mostly sunny during the day Saturday. Warm air being
pumped into western WI out ahead of the approaching cold front on
southwesterly winds will help us to reach lower 80s for highs.

Saturday night and Sunday...Forecast Confidence...Medium

A broad upper trough forms over the Great Lakes with another
modest speed max pushing into southern Wisconsin late Saturday
night. Upper divergence increases with moderate 700 mb upward
motion Saturday evening. The 850 mb thermal ridge is across
southern Wisconsin during the evening, then dropping south into
illinois late. 850 mb dewpoints rise to 14 Celsius. 850 mb winds
are west northwest early evening, then northwest late, becoming
north later Sunday.

The cold front moves across the forecast area Saturday night,
exiting the far south just after sunrise. The cap weakens early
evening, as zero to 1 km mixed layer CAPE rises to almost 2000
Joules/kg. Showers/thunderstorms are expected with the cold front.
GFS forecast soundings are showing a bit more severe potential
with surface to 1 km shear around 22 knots.

Mid, then low level drying behind the front Sunday. A northeast
flow will cool areas, especially near Lake Michigan.

.LONG TERM...

Monday through Friday...Forecast Confidence...Medium

An upper ridge extends into Wisconsin Monday before the upper
flow becomes more zonal Tuesday and Tuesday night. The zonal flow
continues through Wednesday and Thursday and a bit more northwest
Friday, as a broad trough forms near and then just east of the
Hudson Bay area.

Surface high pressure will be over the great Lakes Monday.

A warmer return flow sets up for Tuesday. As the upper flow
becomes more zonal, the chance of thunderstorms will return from
Tuesday evening into Friday with several periods of thunderstorms.
the best chances are Wednesday into Thursday with a heavy rain
potential.

&&

.AVIATION(18Z TAFS)...

Clouds with bases 2000 to 3000 ft range are gradually rising to
greater than 3000 ft and breaking up a little. Light west winds
and mostly clear skies are then expected tonight with high
pressure over the area. Radiational cooling could cause patchy
fog to develop, more likely in south central WI.

Mostly sunny skies Saturday. Then a cold front will track
southeast through WI and could kick up some storms Saturday
evening.

&&

.MARINE...

Light winds and waves tonight with high pressure spreading into
the area. Can`t rule out early morning lakeshore fog because
dewpoints are right around the water temperature, but not enough
confidence to put in the forecast at this time. Increasing
southwest winds will move any lake fog offshore by late morning.

Gusty north to northeast winds are then expected for Sunday into
Sunday evening. Some gusts to 22 knots are possible at times.
Waves may build to 3 to 5 feet during this time. Thus, a Small
Craft Advisory may be needed for Sunday into Sunday night.

&&

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

$$

Tonight/Saturday and Aviation/Marine...Cronce
Saturday Night through Friday...Hentz



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