Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 170851
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
351 AM CDT Sun Sep 17 2017

.SHORT TERM...

Today And Tonight...Forecast Confidence Is Medium.

A negative tilt shortwave over North Dakota will push northeast
into south central Canada this morning, with the upper jet across
the northern Mississippi Valley lifting to the north of Lake
Superior. The upper divergence across southern Wisconsin pushes
off to the north and east this morning. The mid levels dry by
afternoon from the west and southwest. Moisture becomes trapped as
an inversion forms, resulting in a band of high lower level RH.

A cold front will exit southeast Wisconsin by noon. The area of
showers and isolated thunderstorms pushing into south central
Wisconsin is expected to weaken as it moves east.

Drier air surge behind front will reduce threat for late night
fog. In addition, may see an increase in mid-high level clouds
later in the night far southwest areas. Will confine fog mention
to susceptible WI River Valley for the late night.

Monday Through Tuesday Night...Forecast Confidence Is Medium.

Models are generally showing east northeast flow at 500 mb Monday
into Monday night across the region. A vorticity maximum crosses
the area Monday afternoon and evening, providing some differential
cyclonic vorticity advection. A low level jet brings more moisture
into the area during this time. There are some model differences
with the strength and placement of these features over the area,
so some uncertainty exits.

In addition, there is a warm front that sets up to the south of
the area Monday into Tuesday. The NAM brings it and the associated
low level frontogenesis response fields into the area Monday
night, which is an outlier compared to the other models. There is
also some upper divergence from a jet streak around 00Z Tuesday.

Continued to ramp up PoPs Monday, with likely PoPs Monday evening,
then lower later Monday night. Kept thunder for late Monday
afternoon into Monday evening, with weak elevated CAPE on
forecast soundings.

Another low level jet sets up west of the area Tuesday, then
slides toward the area Tuesday night. The best focus for upward
vertical motion seems to be to the northwest of the area. Still,
there is enough moisture that pushes into the area to allow for
some elevated CAPE to develop later Tuesday night. NAM/GFS bring
some QPF into the area Tuesday night, with the ECMWF/Canadian
models not showing much. Kept chance PoPs in the northern parts of
the area for later Tuesday night. Temperatures will remain rather
mild during this time.

.LONG TERM...

Wednesday Through Saturday...Forecast Confidence Is Medium.

Models continue to show a strong and amplifying 500 mb ridge
developing over the eastern part of the country from Wednesday
into next weekend. This sets up southwest flow at 500 mb over the
central and northern Plains. The models are trying to bring a cold
front northeastward into the area later Wednesday into Wednesday
night. It appears that the front weakens and perhaps stalls over
the region during this time. Continued PoPs for Wednesday into
Wednesday night for now. Kept thunder with elevated CAPE lingering
over the region. Warm temperatures are expected to linger.

The front shifts northward later in the week, with warm southerly
winds keeping warm temperatures across the area into next weekend.
This period may end up dry, with the next cold front still west of
the region by later on Saturday. Kept consensus PoPs for now,
until more confidence is gained in the models for this period.

&&

.AVIATION(09Z TAFS)...

Will likely see a period of MVFR ceilings as a cold front moves
through into this morning, per latest models and upstream
conditions. Should see conditions return to VFR for this
afternoon, as drier air moves in behind the cold front.

Showers will be possible at times early this morning, especially
for areas from Madison westward. A rumble or two of thunder is
possible. Showers will wind down in the east this morning, as the
cold front exits.

&&

.MARINE...

An exiting cold front will bring northeast winds to the lake area
this afternoon, as high pressure builds across the northern Great
Lakes. Winds and waves are expected to remain below Small Craft
Advisory levels the next few days.

&&

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

$$

Today/Tonight and Aviation/Marine...Hentz
Monday through Saturday...Wood



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