Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 300224
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
924 PM CDT THU SEP 29 2016

.UPDATE...


&&

.AVIATION/06Z TAFS/...

The MVFR cigs will become more widespread from the east through
the night over se Wisconsin given the closer proximity to the
higher low level moisture content that is associated with the
stalled mid level low over the Ohio River Valley. some ifr cigs
also expected by around sunrise.

Chances for rain increase tonight over southeast WI as the low
pressure area begins to move back toward the Great Lakes. Expect
widespread showers over southeast WI by Friday afternoon, with
scattered showers over south Central WI. These showers will linger
over the area through Saturday morning before slowly tapering off.

Models are showing IFR ceilings during much of the daytime hours
Friday due to deep moisture overhead and scattered to numerous
showers. The models may be overdoing the low clouds because this
is not typical during the day with these breezy conditions, so
there is definitely some uncertainty.

&&

.MARINE...

Blustery north to northeast winds will continue through Friday
resulting in high waves over the near shore waters. This is due to
low pressure sitting over the Ohio River Valley. A small craft
advisory remains in effect through Friday night.

Waterspout threat continues to appear low with the better chance
over the Illinois waters. Expect a round of scattered showers
toward southeast WI later tonight, but especially Friday late
afternoon through Saturday morning.

&&

.PREV DISCUSSION... /Issued 325 PM CDT THU SEP 29 2016/

TONIGHT AND FRIDAY - Forecast Confidence...Medium.

Low pressure sitting over the Ohio River Valley is causing a
prolonged period of breezy north to northeast winds across southern
WI this week. Another surge of moisture will wrap counterclockwise
around the low into southeast WI this evening. Moisture will be
concentrated in the lower levels, so any showers are not expected to
be widespread and should be confined to far southeast WI and
northern IL overnight. Friday morning, there should be a few showers
over southern WI due to steady theta-e advection, but nothing
widespread.

Deeper moisture will spread from east to west into southern WI
Friday morning as the low retrogrades a little to the northwest.
Expect more widespread showers to expand into south central WI
during the afternoon hours.

Low temperatures will be in the mid to upper 50s tonight except
toward western and central WI. The longer the clouds take to spread
inland, the cooler the temperatures will end up. Highs Friday will
be cooler than today due to extensive clouds, especially in
southeast WI, with highs in the lower 60s.

FRIDAY NIGHT THROUGH SUNDAY - Forecast Confidence...Medium.

Focus of this period on effects from upper low that will be
meandering over the western Ohio and central Mississippi Valley
regions.  Currently, the upper low is located in the southern
IN/northern KY region.  Short term guidance is in good agreement on
upper low drifting northward in response to weak upstream short wave
moving east through the southern Plains.

As the low drifts northward later Friday and Friday night, a mid-
level jet core and short wave trof will move wwd across Michigan
into Wisconsin. Column moisture not a problem as precitable water
values will be in the 1-1.25 inch range Friday night into Saturday.
Enough upper level divergence and isentropic omega associated with
this feature to warrant beefing up the pops to categorical levels
across the eastern CWA Friday night.  Drier air eventually working
into the circulation of the upper low late Friday night through
Saturday will result in the shower threat diminishing.

Also, the upper low will get nudged northeast into the central and
eastern Great Lakes Saturday night and Sunday bringing an end to the
showery weather across southeast Wisconsin. Persistent clouds and
cool northern breezes will keep temperatures peaking near or
slightly below seasonal normal.

EXTENDED PERIOD...

SUNDAY NIGHT THROUGH THURSDAY - Forecast Confidence...Medium.

Upper low will continue to track ENE across the eastern Great Lakes
Sunday night and Monday, away from Wisconsin as short wave ridging
spreads across the Upper Midwest into the western Great Lakes.  This
will result in quiet, dry weather for the first half of next week
with temperatures rebounding to around seasonal normal for early
October.

The extended guidance diverges in the late periods as GFS has been
trending toward upstream long wave progressive trof changing into
cutoff upper low in the central Plains by around mid-week.
Meanwhile, ECMWF and latest GEM-NH showing more progressive long
wave trof taking on a more negative tilt as it moves northeast
through the upper midwest.  12z GFS also appears to be transitioning
to this more progressive solution.  This scenario would bring
frontal boundary across WI around Thursday so will continue to
include small chance for convection.  Player in later periods of the
forecast will be timing and track of tropical disturbance that will
move through the western Atlantic late next week into the weekend.

GFS 5-Day 500H anomoly showing large positive height anomoly over
southern Canada with more zonal flow and near normal heights setting
up over the Upper Midwest by early the following week.

AVIATION/00Z TAFS/...

The MVFR clouds will persist through the night over se WI given the
closer proximity to the higher low level moisture content that is
associated with the stalled low over the Ohio River Valley. There
are also a few light showers sneaking into far southeast WI this
afternoon as well.

Chances for rain increase tonight over southeast WI as the low
pressure area begins to move back toward the Great Lakes. Expect
widespread showers over southeast WI by Friday afternoon, with
scattered showers over south Central WI. These showers will linger
over the area through Saturday morning before slowly tapering off.

Ceilings will fall to 1000 ft later tonight in southeast WI. Models
are showing IFR ceilings during much of the daytime hours Friday due
to deep moisture overhead and scattered to numerous showers. There
could also be patchy fog with the precip. The models may be
overdoing the low clouds because this is not typical during the day
with these breezy conditions, so there is definitely some
uncertainty.

MARINE...

Blustery north to northeast winds will continue through Friday
resulting in high waves over the near shore waters. This is due to
low pressure sitting over the Ohio River Valley. A small craft
advisory remains in effect through Friday night. The coast guard
reported 7 foot waves 1.5 nm east of Sheboygan Lighthouse around 3
pm today.

Waterspout threat continues to appear lower than yesterday. Expect a
round of scattered showers toward southeast WI later tonight, but
especially Friday late afternoon through Saturday morning.

MKX WATCHES/WARNINGS/ADVISORIES...

WI...None.
LM...Small Craft Advisory LMZ643>646 until 4 AM CDT Saturday.

$$
TONIGHT AND FRIDAY/AVIATION/MARINE/BEACHES...MRC

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...SMALL CRAFT ADVISORY until 4 AM CDT Saturday for LMZ643>646.

&&

$$

UPDATE...Hentz
TONIGHT/Friday AND AVIATION/MARINE...MRC
Friday NIGHT THROUGH Thursday...Davis


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