Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 200814

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
314 AM CDT Sun Aug 20 2017

.TODAY AND TONIGHT...Forecast Confidence Is Medium.

The main question for today is whether some of the convection
across Iowa will sneak into far southwest Wisconsin later this
morning and afternoon. The models are a mixed bag with it. They
seem to be latching onto some sort of MCV, or mid level short wave
and firing off convection with it. We will struggle to have
enough moisture and instability to support that. Given trends at 2
am this morning, it seems reasonable to doubt that scenario. The
better airmass is southwest of Wisconsin, so the progress of the
convective complex to the west should stay just out of the state.
Will carry a very small POP southwest of Madison just in case,
but, in general, the area should be dry and warm today.

There`s a better chance, though not great, that we could see some
showers and storms tonight. Again, the better focus should be
across Iowa where convergence along a frontal boundary, combined
with a more unstable airmass, should result in a complex of storms
that would eventually trend east southeast with time. We will be
within a zone of rather deep warm and moist air advection across
southern Wisconsin tonight with elevated instability and an
increasing low level jet. The models do show some showers and
storms developing within this region across southern Wisconsin.
Worthy of a 30-40 pop for now.

.MONDAY THROUGH TUESDAY NIGHT...Forecast Confidence Is Medium.

Models are generally showing the low level jet and steady warm air
advection continuing to pump warm and humid conditions into the
area Monday into Monday night. There may be some debris clouds
from convection passing through or to the south during the
morning. Frontal boundary remains to the north of the area as
well. There may be somewhat of a lull in any showers and
thunderstorms Monday, with rather weak upward vertical motion
fields. Kept chance PoPs for now. There may be a good amount of
cloud cover midday into middle afternoon Monday, which may limit
the viewing of the solar eclipse.

High PoPs for showers and thundestorms will continue for Monday
night, as the best low level frontogenesis response with the cold
front pushes through the area. This combines with fairly strong
upper divergence from right entrance region of 250 mb jet streak.
There is fairly robust mean layer CAPE, though some models are
overdone on dewpoints. Deep layer bulk shear is around 30 to 35

This combination brings a risk for strong to severe storms, per
SPC Day 2 slight risk over most of the area. This may be in the
form of an MCS moving through the area Monday night. Some models
suggest this may shift to the south of the area, while others
bring it east through the area. Heavy rainfall would also be a
concern, with precipitable water values around 2 inches and
favorable warm cloud depth. Slow storm propagation may allow for
some training of storms.

Hung onto PoPs mainly Tuesday morning in the the area, until the
front is totally out of the area. The afternoon may end up dry,
with strong cold air advection pushing into the area from the
northwest. It may take some time for dewpoints to drop to more
comfortable levels Tuesday. Closed low at 500 mb northeast of
Lake Superior will bring northwest flow over the area into Tuesday
night. Cooler and drier conditions are expected for Tuesday

.WEDNESDAY THROUGH SATURDAY...Forecast Confidence Is High.

This period looks fairly dry and cool over the area, as northwest
flow at 500 mb prevails over the region. There is decent
agreement with high pressure sliding slowly southeastward across
the region Wednesday into Friday, before sliding to the east into
Saturday. Temperatures look to be below seasonal normals, with
highs in the 70s and lows in the 50s. This will be an early taste
of autumn air.



VFR conditions are expected through the TAF period. The
exceptions would be some early morning fog with reduced
visibilities through about 13-14z this morning. But, that fog
should be mostly out in the countryside and may hit KMSN. There is
a chance of showers and thunderstorms tonight. Any stronger
convection would bring a temporary lowering of conditions. Look
for light winds this morning turning southerly and increasing to
about 10 to 15kts.



Southerly winds will increase to 10 to 20 knots today, especially
up toward Sheboygan. The highest waves will also be up toward
Sheboygan. The southerly winds will relax a bit on Monday and
eventually shift to the northwest on Tuesday in the wake of a
surface trough and cold front moving through. Winds and waves
should remain below Small Craft Advisory levels for much of next




Today/Tonight and Aviation/Marine...Davis
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