Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 191057
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
557 AM CDT Thu Jul 19 2018

.UPDATE...

The forecast remains on track. The lastest 06z model runs aren`t
showing any significant deviations on timing, etc.

&&

.AVIATION(12Z TAFS)...

A slow moving low pressure system will push into southern
Wisconsin tonight. Look for mainly VFR conditions through this
evening. Showers and a few thunderstorms will push into south
central Wisconsin this afternoon and overspread all of southern
Wisconsin tonight. Conditions should begin to lower to MVFR
levels after about 09z Friday, especially in the KMSN area. Those
lower conditions will spread east into Friday morning.

&&

.PREV DISCUSSION... (Issued 324 AM CDT Thu Jul 19 2018)

SHORT TERM...
Today and tonight...forecast confidence is high.

The scenario remains largely unchanged. A slow moving
closed/stacked low pressure system will approach the area today,
spreading some showers and possible thunderstorms into the area
this afternoon. We should manage to stay dry through early
afternoon, but leading warm air advection and diurnal trends
should allow some bands of showers/storms to overspread mainly
south central Wisconsin this afternoon. We`ll have some initial
dry air to overcome before the rain arrives, but things will
moisten up.

The low pushes into southwest Wisconsin tonight. This is a
southern shift compared to what we were looking at 24 hours ago.
Given this is a closed/occluded/stacked low, the precipitation
will be banded and therefore hard to pin point exactly where the
more generous rainfall will occur. Precipitable water values will
climb to around 1.8 inches, a bit higher than earlier forecasts.
The combo of the high moisture and the banded precip suggests
locally heavy rainfall possible. Not much concern for flooding as
amounts will likely stay under that threat and agriculture is
really thirsty right now, so not much in the way of runoff. CAPE
and shear values are rather low, so not much concern for severe
weather. That focus is out toward Iowa. Our southwest corner could
see a narrow axis of better instability late this afternoon and
evening, justifying a marginal risk out there. This is a badly
needed and very beneficial rainfall.

LONG TERM...
Friday through Sunday...Forecast confidence is high.

The vertically stacked surface and mid level low tracks across
southern Wisconsin on Friday and Lake Michigan Friday night. Expect
widespread showers with the low overhead. PWs will be around
1.75 inches so heavy down pours can be expected at times. There
is a chance of thunderstorms on Friday with 500-1000 J of Cape.
Instability diminishes overnight so thinking just rain showers,
although can`t rule out a thunderstorm with a little elevated
instability.

Models are in good agreement showing high temperatures around 70 for
Friday and Saturday.

The low slowly sags southeast on Saturday maintaining its
influence over the region. Waves of vorticity within cyclonic
flow associated bring continued chances for precipitation,
especially for eastern WI closer to the low. A few hundred Joules of
cape warrant the mention of thunder. Small precip and thunder
chances continue into Sunday for eastern Wisconsin until the upper
low moves further away.

Monday through Thursday...Forecast confidence is medium.

Mid level ridging moves in for Monday bringing dry weather. Models
differ whether a cold front moving through Monday night or Tuesday
will have precip with it. Another front looks to move through
later in the week with some precip but there is uncertainty with
the timing. There is pretty good model agreement showing highs in
the 70s or lower 80s at times.

AVIATION(09Z TAFS)...

A slow moving low pressure system will push into southern
Wisconsin tonight. Look for mainly VFR conditions through this
evening. Showers and a few thunderstorms will push into south
central Wisconsin this afternoon and overspread all of southern
Wisconsin tonight. Conditions should begin to lower to MVFR
levels after about 06-09z Friday, especially in the KMSN area.

MARINE...

Increasing southeast winds ahead of an approaching low pressure
system will bring small craft advisory conditions later tonight
through Friday. Northerly winds on the back side of the low will
likely result in small craft advisory conditions later Saturday
into Sunday.

BEACHES...

Increasing southeast winds tonight will result in building waves
and a threat for rip currents. A beach hazards statement is in
effect for Sheboygan county, south to Kenosha from midnight
tonight through early evening on Friday.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement from late tonight through Friday evening
     for WIZ052-060-066-071-072.

LM...Small Craft Advisory from midnight tonight to 7 PM CDT Friday
     for LMZ643>646.

&&

$$

Update...Davis
Today/Tonight and Aviation/Marine...Davis
Friday THROUGH Wednesday...Marquardt


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