Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 260005
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
705 PM CDT Mon Sep 25 2017

.UPDATE...Showers and isold tstorms west of Madison
have been mostly initiated by outflow boundaries from previous
convection. Expect the showers and storms to gradually weaken over
the next few hours but may not completely dissipate as the sfc
trough is nearby. Pressure falls will occur over nw WI tnt with
low pressure developing newd across Lake Superior on Tue. Thus the
cold front will slowly progress ewd across srn WI. Dynamics and
heights falls will be very minimal on Tue as the main upper trough
over the nrn and central Rockies lifts newd into the nrn Great
Plains and Canada. The sfc convergence along the broad front will
be weak as well, thus only chances of showers and tstorms on Tue.


&&

.AVIATION(00Z TAFS)...Areas of fog may form late tnt mainly west
of Madison where rainfall has occurred this evening. The passage
of a cold front on Tue will bring chances of showers and tstorms
but the lowest Cigs should remain from 5-7 kft.


&&

.PREV DISCUSSION... (Issued 306 PM CDT Mon Sep 25 2017)

SHORT TERM...

Tonight and Tuesday...Forecast confidence...High

A lead upper shortwave moves into the northwest Minnesota
region Tuesday afternoon, with the upper jet across eastern
Minnesota and northwest Wisconsin as it increases. Upper level
divergence is neutral or weak across southern Wisconsin until
Tuesday afternoon as the upper divergence moves across southern
Wisconsin. 700 mb upward motion increases tonight south central
sections and across southern Wisconsin Tuesday. 700/850 mb RH
increases slowly south central tonight and across the southeast
Tuesday. Surface based CAPE west and northwest of Madison rises to
1250 Joules/kg, but only around 700 Joules/kg of zero to 1 km
mixed layer Cape. With the marginal forcing and shallow layer of
moisture around 750 to 800 mb, will keep shower and thunderstorm
chances in the low to medium range south central and mainly low
southeast Tuesday.

The surface cold front does make it through south central
Wisconsin Tuesday afternoon.

Tuesday night and Wednesday...Forecast confidence...Medium

The lead upper shortwave moves to the north of lake Superior
Tuesday night, with the upper jet laying out across Wisconsin
Wednesday. Moderate upper level divergence overnight, lingering
far southeast Wednesday morning. Moderate 700 mb upward motion
southeast Tuesday evening, then downward motion spreading in from
the west. Little in the way of zero to 1 km mixed layer Cape.
Soundings do show moistening over the atmospheric column Tuesday
night southeast. With the marginal forcing lifting northeast,
will keep shower chances in the low range. The surface cold
front makes it through southeast Wisconsin Tuesday evening. Strong
drying occurs Tuesday night and Wednesday behind the cold front.

LONG TERM...

Thursday through Saturday...Forecast confidence is Medium

The base of the upper trough moves across the Upper Mississippi
Valley Thursday, and over the Great Lakes Friday. Cooler air (near
normal) is expected, with some instability showers possible with
the upper trough, mainly Thursday night, and then southeast
Friday.

Upper ridging moves across Friday night and Saturday.

A large surface high moves across Saturday.

Sunday and Monday...Forecast confidence is Medium

An upper level trough moves into the Northern Rockies Sunday

Warm air advection begins on Sunday with a chance of showers
Monday.

AVIATION(18Z TAFS)...

VFR conditions will continue through the TAF period. Expect
scattered fair weather cumulus this afternoon. Conditions look
dry, with any showers or storms remaining west of Madison through
12z Tuesday.

MARINE...

Winds and waves will remain below small craft advisory
levels through the week. A cold front will push through the region
Tuesday evening, switching winds from southerly to northwest
behind the front. That will also come with a chance of showers or
a thunderstorm.

&&

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

$$

Update...Gehring
Tonight/Tuesday and Aviation/Marine...Hentz
Tuesday Night through Monday...Hentz



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