Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 252014

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
314 PM CDT TUE OCT 25 2016


Tonight and Wednesday...Forecast confidence is high.

Models are remaining quite consistent for rain spreading into
southern WI this evening. There is better agreement with the surface
low tracking across northern IL overnight. I only made small
adjustments to the arrival times. The band of higher reflectivity
showing up on the regional radar is due to an area of 250-850mb
differential divergence, weak 500mb differential vorticity
advection, and 700mb frontogenesis. Cloud bases with this feature
are around 10,000 feet, so only sprinkles are possibly reaching the
ground this afternoon in southeast WI.

Weak low level theta-e advection is helping to create some low
clouds over southern WI today, just to the north of the upper level
banded precip feature. This is creating a smaller gap between the
upper level and lower level moisture and could lead to an earlier
precip arrival time late this afternoon/early evening.

Expect 700mb frontogenesis to strengthen over south central WI early
this evening 00z/7 pm. This should be enough forcing to help
saturate the low levels enough for scattered rain showers to
develop, although it will still be spotty.  Between 10 pm and
especially midnight, steady rain will spread into Madison due to
deep saturation, stronger differential vorticity advection, 925-850
frontogenesis, persistent strong 700mb frontogenesis, and the nose
of the low level jet. This strong forcing will slowly track east
across southern WI overnight through Wednesday afternoon. Strong
dynamics and steeper lapse rates aloft could lead to a few rumbles
of thunder- pretty low chance.

East winds will increase rapidly Wednesday morning as the low
approaches. Blustery east winds driving a steady rain with low
clouds will lead to a raw, fall day. Max temperatures will only be
in the upper 40s.

Wednesday night through Saturday...Forecast confidence medium.

The shortwave trough over central or srn WI early Wed evening will
move to lower MI by midnight with the surface low tracking from
nrn IL to wrn Lake Erie by 12z Thu. Light rain will linger into
the evening especially over ern WI.

A weak ridge of high pressure will build into the area on Thu
with 500 mb height rises. A stratus deck will likely begin the day
but may thin for the afternoon. However, more clouds may occur as
850-700 mb warm advection ensues over wrn WI. Was conservative
with high temps around 50F.

The surface ridge will move east Thu evening with strengthening
sly winds through Fri night as low pressure moves across the nrn
Great Plains into the nrn Great Lakes. The trailing cold front may
not pass until Sat night so warmed temps into the 60s for Fri-
Sat. 70F temps could be possible Sat as 850 mb temps warm to 17c
and 1000-500 mb thicknesses to 564-567 DM.

.LONG TERM...Sunday through Tuesday...Forecast confidence medium.

A cold frontal passage is expected Sat night with high pressure
building into srn WI for Sun afternoon. There is a chance of
showers Sat night with the fropa over the nrn cwa. Another strong
low will then track across the nrn Great Plains to the nrn Great
Lakes bringing another surge of warm air for Mon. There are small
chances of rain with the surge of warm air Mon am. The cold front
will pass Mon night with high pressure for Tue. Temps will remain
above normal during this period.



Regional radars are showing a band of rain over southwest WI this
afternoon, but only a few light showers and sprinkles are reaching
the ground due to a very dry low level airmass. Meanwhile, there is
a low cloud deck (2500 feet AGL) across southern WI that is slowly
creeping north. Over time, this dry air will erode away and rain
will efficiently reach the ground.

Steady rain will spread west to east across southern WI from around
9 pm through 3 am and persist through most of Wednesday afternoon.
There could be a few rumbles of thunder with the heavy rain late
tonight/Wed morning. Expect IFR ceilings and MVFR visibilities with
this period of heavy rain.

East to southeast winds will increase rapidly late tonight and
especially Wednesday morning. Gusts to 30 knots are expected in
southeast WI.



A Gale Warning has been posted for Wednesday into Wednesday evening.
East to southeast winds will ramp up quickly later tonight in
response to strong low pressure approaching from the west.  Gale
force gusts to near 40kts are expected on Wednesday, diminishing
quickly Wednesday evening.  Waves will build quickly with the
highest conditions here on the west side of the lake.  The low will
pass south of Wisconsin Wed night with high pressure and light winds
expected on Thursday.


.MKX Watches/Warnings/Advisories...
LM...GALE WARNING from 7 AM to 10 PM CDT Wednesday for LMZ643>646.



Wednesday NIGHT THROUGH Tuesday...Gehring is the U.S. government's official web portal to all federal, state and local government web resources and services.