Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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634
FXUS63 KMKX 250149
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
849 PM CDT Sat Jun 24 2017

.UPDATE...

Very impressive circulation on water vapor imagery of the mid
level shortwave tracking across central WI attm. Showers in the
leading PVA are will push out of southeast Wisconsin around 10 pm.
Impressive and rather surprising winds with the showers. There
was no thunder once this stuff got into south central WI. The dry
air these showers moved through, coupled with the very cold air
aloft, helped to sustain the cold, gusty winds. The potent
shortwave kept them alive despite the unfavorable airmass.

Things will quiet down tonight. More showers Sunday afternoon, but
not as robust.

&&

.MARINE...

Westerly winds will persist through Monday, but should remain
below small craft advisory conditions. The off shore winds will
keep any higher waves well off shore.

&&

.PREV DISCUSSION... (Issued 554 PM CDT Sat Jun 24 2017)

AVIATION(00Z TAFS)...

A cluster of showers and storms will race across southern
Wisconsin this evening. They are near the city limits of Madison
at 6 pm and will reach Milwaukee just before 8 pm. Expect these
showers on and off for a few hours once they arrive. This activity
will begin to dissipate as they reach southeast Wisconsin due to
the diurnal loss of heating. Winds to 30-35kts can be expected in
the Madison area and probably 20-25kts in Milwaukee. VFR
conditions will persist through the TAF period. A similar scenario
can be expected Sunday afternoon, but just not as potent as this
evening`s activity.

PREV DISCUSSION... (Issued 208 PM CDT Sat Jun 24 2017)

DISCUSSION...

Tonight and Sunday...Forecast confidence is high:

Main circulation with approaching wave is currently over southeast
MN and will continue to approach this afternoon. Showers and a few
storms associated with this system will move into the western
forecast area between 5 and 6 pm per latest meso models. Activity
is still expected to diminish in strength and coverage as it moves
eastward across the forecast area this evening.

Should be dry with less clouds late evening into early Sunday
morning. The next in a series of waves is then progged to bring
more shower chances Sunday afternoon. A rumble or two of thunder
will be possible as well. Temps and winds will be similar to
today, a fairly cool day for late June.

Monday - Confidence...Medium
A mid level low will shift from vcnty ern WI into lower MI. We
will remain in the influence of a cyclonic flow throughout the
day. Instability is shallow but there nonetheless and the models
are showing some QPF. So will carry at least small POPS to account
for the cyclonic flow and instability.

Tuesday - Confidence...Medium
Surface high pressure will dominate with quiet weather expected.
Overall a benign northwest mid level flow. Still some lingering
influence of the low level thermal trough but by and large a trend
towards modifying temps gets underway with a weak southerly return
flow setting up.

Wednesday and Wednesday night - Confidence...Medium
The start to a more active pattern takes shape with the mid level
ridge axis shifting to the east and short wave energy riding
through on a wsw mid level flow. In addition there will be a
fairly pronounced southwest LLJ. The primary low pressure center
will be moving well to our northwest and north. So could end up
seeing a few rounds of storms with the initial waves of energy and
LLJ as well as the trailing cold front as it moves into the area
Wednesday night.

Thursday - Confidence...Low to Medium
Frontal position will be key player for the focus of convection.
At this time the models have this feature south with the LLJ
shifted to our east. A renewed LLJ in the southern Plains should
focus development further to our south. However some uncertainty
on how quick the 850 front slides south of the state line so with
that in mind will keep the Superblend POPS in place as some
convergence may linger. At this time the GEM is the only model
showing a dry solution.

Thursday night through Friday night - Confidence...Low to Medium
A wave of low pressure is proggd to move along the front and this
would likely push the front back into WI. More rounds of
thunderstorms are expected during this period. There are some
timing differences as well with the ECMWF quicker on moving this
out by later Friday while the GFS would linger convection into
Friday night.

Saturday - Confidence...Low
The ECMWF drops in another low but from the north and keeps the
precip mainly across northern and central WI. Meanwhile the slower
GFS would suggest the slower movement of the southern low would
result in lingering chances of showers/thunderstorms especially in
the morning. Will stick with the Superblend guidance at this
time.

AVIATION(18Z TAFS)...Could see an isolated shower or two through
late afternoon, with the main area of showers then moving through
west to east early this evening. Still expect the showers to diminish
as they move through the forecast area given the loss of daytime
heating. Best chance for some thunder will be from Madison westward
where there will still be a little instability when the showers
arrive.

Looks quiet then overnight into Sunday morning. Another shortwave
is expected to bring more showers tomorrow afternoon. Could be a
couple rumbles of thunder too.

Other than briefly lower visibilities in heavier rain showers, VFR
conditions will prevail through Sunday.

MARINE...West to northwest winds will be on the breezy side through
Monday, but are expected to stay just below Small Craft Advisory
levels. A few gusts to 25 knots are not out of the question.

&&

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

$$

Update...Davis
Tonight/Sunday and Aviation/Marine...Collar
Sunday Night through Saturday...DDV



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