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Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI
236 PM CDT Tuesday Sep 2 2014

Short term...

Tonight and Wednesday...forecast confidence...high

A few showers over the northeast forecast area will diminish by the
evening hours. Looks quiet tonight with light winds and mostly clear
skies due to high pressure centered to the south. Could see some
patchy fog...particularly in the southern half of the forecast area
toward the center of the high.

Looks pretty quiet then Wednesday with mostly sunny skies in the
morning and increasing middle and high level clouds west in the
afternoon. High temperatures will be a tad above normal tomorrow into the
upper 70s and low 80s.

Wednesday night and Thursday...forecast confidence is high

A weak ridge tries to briefly build into Wisconsin as the
middle/upper shortwave approaches North Dakota and southern Manitoba.
The strong 100 knot jet maximum stays well north across northern
Minnesota to near and north of Lake Superior. Weak upper
divergence initially over southern Wisconsin...then the NAM has
several areas of moderate to strong upper divergence...which
appears to convective feedback.

The 45 knot 850 mb low level jet reaches west central and far
southwest Wisconsin by Wednesday evening...then increases to 55
knots as it moves across much of Wisconsin by midnight...before
weakening. 850 mb dew points rise to 15 to almost 20 celsius
over much of southern Wisconsin. Elevated cape increases to 1500
joules/kg if lifted from just above the shallow low level
inversion. 700 mb upward motion is weak to moderate.

The NAM lifts the surface and 925mb warm front northeast through
the forecast area Wednesday night. This brings precipitation
across much of the forecast area on most forecast models. The GFS
has heavy rainfall amounts with the NAM and 00z European model (ecmwf) keeping the
far southwest and south central sections in much less rainfall.

Then the bulk of the showers and thunderstorms are to the north
Thursday afternoon with southern Wisconsin in the humid warm
sector. Zero to 1 km mixed layer cape values are around 3800
joules/kg Thursday afternoon with a cap of around 60 to 100
joules/kg around 860 mb in the southeast...that weakens to only
around 2 joules/kg by evening in areas northwest toward The
Dells. Nsharp severe parameters increase in this area. Any
supercells would be high precipitation...but with a strong 55
knot wind at 700 mb any upstream linear mesoscale convective system would push rapidly
east. Most of the forecast area is in a slight risk of severe.

Thursday night and Friday...forecast confidence is high

The NAM/GFS and European model (ecmwf) have a southwest flow across Wisconsin as
the strong shortwave moves across south central Canada with the
strong 105 knot jet across the Lake Superior area Friday evening.

The NAM continues to show high zero to 1 km mixed layer cape
values of 3800 joules/kg through the evening ahead of the
advancing cold front with the cap weakening. The severe potential
will continue until the cold front exits the far southeast after
midnight during the early Friday morning.

Only some lingering showers expected after sunrise in the far
southeast given the NAM/GFS/ECMWF model speed of the front.

Cold air advection on north winds Friday afternoon with the drier

Long term...

Friday night and Saturday...forecast confidence is high

The middle/upper trough heads into southeast Canada with a second
trough over south central Canada...with a rather fast west flow
over Wisconsin.

Both models push the surface front well to the south...reaching
Kentucky on Saturday. Cool high pressure builds into Wisconsin
from the northern and Central Plains.

Sunday and Monday...forecast confidence is high

The flow is zonal Sunday and Monday with a trough beginning to dig
into the northwest U.S. That begins to push east on Monday.

A large surface high is expected to extend across the Great Lakes
region Sunday. This high still extends back into Wisconsin on

Tuesday...forecast confidence is high

A large trough extends from western Canada into the northern and
Central Plains.

Low level south flow affects Wisconsin ahead of low pressure in
the plains. Both the GFS and 00z European model (ecmwf) keep any return
precipitation to the west.


Aviation/00z tafs/...

A few showers over the northeast forecast area will diminish by the
evening hours. Main concern tonight then is the potential for some
fog development. Winds will be light and skies mostly clear as high
pressure slides by to the south. Best chance for some 2 to 5 sm fog
will be across the southern half of the forecast area toward the
center of the high. Could see some very brief dense fog in a few
locations...particularly in river valleys.

VFR conditions are expected on Wednesday...with increasing middle and
high level clouds west by late afternoon.



A Small Craft Advisory may be needed southwest winds
are expected to gust to around 25 knots.


Mkx watches/warnings/advisories...


Tonight/Wednesday and aviation/marine...ddv
Wednesday night through Tuesday...hentz

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