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Area forecast discussion 
National Weather Service Green Bay WI
1055 PM CDT Sat Aug 30 2014

Updated aviation portion for 06z taf issuance

issued at 233 PM CDT Sat Aug 30 2014

Warm and rather humid weather will showers and thunderstorms at
times through the middle of next week.

Pretty typical late Summer upper level pattern in place across
noam. Broad band of westerlies was across the northern Continental U.S. And southern
Canada. Those will strengthen further and sag southward during the early
part of the forecast period...then weaken and recede northward during the
latter half of the period. A series of shortwaves progressing through
the pattern will interact with frontal boundary expected to remain
stetched out west-east along the southern edge of the main westerlies...
bringing several opportunities for precipitation to the forecast area.

Temperatures are expected to remain at or above normal for much of the forecast
period before dropping back close to normal late. It will also be
humid at times. The pattern looks favorable for above normal precipitation
amnts...though timing of the precipitation becomes more difficult after
the first couple days of the forecast.

Short term...tonight and Sunday
issued at 233 PM CDT Sat Aug 30 2014

Several concerns to deal with...mainly during the tonight part of the
forecast. These concerns include: when to end the precipitation much
fog will develop and min temperatures.

The 19z msas surface analysis indicated an area of low pressure just south
of esc with a cold front stretched southward along the Western Shores of Lake Michigan
and a secondary trough extended west-SW through SW WI. Farther west...a
ridge of hi pressure stretched from western Ontario southward to the Central Plains.
Vsbl satellite imagery showed a plethora of clouds over WI rotating
around a shortwave trough in the middle-levels of the atmosphere. Local
radar mosaic picked up several bands of light to moderate showers
over the eastern three-quarters of WI with a steady east-NE movement.

The trailing shortwave trough/embedded shortwave to still cross WI
this evening and may have to linger a pop at least over eastern
sections of the forecast area where dew points are still relatively
high. Once these features depart overnight...weak ridging both at the
surface and aloft to move into the western Great Lakes. Weak subsidence
and modest drying could brieft break the cloud cover up...however
this would lead to fog development especially after all the rain
we have seen over the past 36 hours. Expect fog to develop around
the midngt hour and could become quite thick toward daybreak
mainly across northern and central WI where the higher rainfall totals
occurred. No headlines yet...but later shifts will have to watch
this closely. Min temperatures to range from the upper 40s to lower 50s
north...middle to upper 50s south.

The fog will burn off by mid-morning...leaving some sunshine for
Sunday as the ridging shifts off to the east. Do expect to see
middle/hi clouds begin to approach central WI Sunday afternoon ahead of
an impressive looking system moving into the upper MS valley. Look
for maximum temperatures to range from the middle to upper 70s north...around 80
degrees south (cooler near lake mi).

Long term...Sunday night through Saturday
issued at 233 PM CDT Sat Aug 30 2014

Shortwave progressing eastward from the northern plains will generate cyclone over
the upper Midwest during the latter part of the Labor Day
weekend. The NAM seemed way overdone with the strength of the
cyclone and was discounted. The most likely scenario seems to be
for severe storms to fire out to the west sun aftn/evening...then
move east. They should be weakening before they arrive in the
area...though can/T rule out severe winds/hail Sun night...especially as low level jet
gets directed into the western part of the forecast area late Sun night. The
storms will likely still be across the area Monday morning...then the
question is whether or not they exit quickly enough to allow for
another round of storms Monday aftn/eve. The European model (ecmwf) is a definite no-
vote. It/S slower arrival of the lead convection and faster
arrival of the cold front shortens the window between convective
events on both sites...leaving little time for air mass recovery.
Little ended up happening across the forecast area in a similar
scenario this past Monday. Did not make major changes to probability of precipitation from
previous forecast...but will lean toward the European model (ecmwf) solution and forego playing
up Monday afternoon/evening severe risk in the severe weather potential statement.

Timing of precipitation chances becomes the primary challenge in later
periods. That shows itself already Tuesday. Although a few of the
models still generated precipitation...the trend on most was to have the
forecast area dry and between systems. Although it/S hard to absolutely
rule out precipitation...given rising upper heights and surface Ridge Crossing
the area...the support for sig precipitation is trimmed probability of precipitation.

No sig changes need to broad-based extended forecast initialization

Aviation...for 06z taf issuance
issued at 1052 PM CDT Sat Aug 30 2014

Questions will be ceilings and visibilities tonight as weak surface high
moves in. Some breaks in clouds continue given latest satellite
though with light winds and plenty of lingering low level moisture
expect any clearing will be replaced by IFR ceilings and/or visby
clearing by middle day Sunday. Next frontal system to approach the
arrea late in the taf period. Have increased clouds once
more...though will hold off precipitation until after 06z. &&

Grb watches/warnings/advisories...


short term.....Kallas
long term......skowronski

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