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Area forecast discussion 
National Weather Service Green Bay WI
1205 PM CDT Tuesday Oct 13 2015

Updated aviation portion for 18z taf issuance

issued at 319 am CDT Tuesday Oct 13 2015

Temperatures much more typical of October expected this week.

Strong shortwave that crossed the region yesterday will contribute to the evolution
of broad lngwv trough over eastern noam the next couple days. Meanwhile
back to the west...the sharpening of upper ridge along the West
Coast will result in the next shortwave digging farther west...further
amplifying the eastern noam lngwv trough...and temporarily pulling it/S
axis westward a bit by the weekend. The flow should become more
progressive and trend toward lower amplitude during the latter
part of the forecast period.

The development/amplification of the eastern noam lngwv trough will result
in much cooler temperatures than this past weekend. After a noticeably
cooler day today...temperatures will rebound a bit middle-week before dropping
to rather chilly levels for late in the week and the start of the
weekend. Although there will be a couple opportunities for
precipitation...none of them appear to have sufficient moisture to result
in significant rainfalls.

Short Wednesday
issued at 319 am CDT Tuesday Oct 13 2015

The main change to the forecast was to linger cloudiness longer into
day...and into tonight over the NE. It/S common for clearing to occur
slowly with northwesterly flow across Lake Superior in the fall/early
winter...and that seems likely to be the case tda/tngt. Radar/surface
observation also indicated light precipitation continuing across the north. Lingered rain showers/dz
through most of the morning. A few showers recently affected the
southern part of the forecast area...though those seem to be mainly southeast of
the area now. Will make some final tweaks at issuance time.

Quiet weather is expected Wednesday as anticyclone passes SW of the area. The
added sunshine combined with some warm air advection should allow temperatures to edge
back to a little above normal.

Long term...Wednesday night through Monday
issued at 319 am CDT Tuesday Oct 13 2015

Models appear to be in good agreement with the mean flow
consisting of a western Continental U.S. Upper ridge/eastern Continental U.S. Upper trough through the end
of the work week. The upper ridge is forecast to push eastward into the central
Continental U.S. Next weekend and weaken in the process. By early next
week...a new upper trough to be pushing into The Rockies with a
somewhat zonal flow over the eastern half of the Continental U.S.. for NE WI...
this pattern will send temperatures below normal after Thursday with precipitation chances
mainly focused on Thursday with the passage of a shortwave trough/cold front
and next Monday associated with warmer air attempting to return to
the Great Lakes region.

As the center of an area of hi pressure shifts into the Tennessee Valley
Wednesday night...the northwest flow aloft will send a modest cold front into the western
Great Lakes. Moisture ahead of this fnt over WI is severely
lacking and with all the middle-level forcing and jet dynamics
trailing over SW Ontario/upper MS valley...prefer to run with the
dry forecast Wednesday night with perhaps some late night clouds arriving with
the fnt. Min temperatures to range from the middle to upper 30s north-central WI...
lower to middle 40s near Lake Michigan. The cold front pushes through the forecast area
Thursday morning...however the better forcing/dynamics arrive Thursday
afternoon associated with a strong shortwave trough and its embedded
shortwave. This feature may be able to squeeze out some light
showers...despite a lack of low-level moisture. Have kept probability of precipitation on
the low side for now. Maximum temperatures will range from the lower to middle 50s
N-cntrl...lower 60s east-central WI (slightly cooler near lake mi).

A pretty good shot of cold air advection is prognosticated to overspread the region
behind this system starting Thursday night as the 800 mb temperatures are expected
to drop into the negative single digits (c) by 12z Friday. Prevailing
northwest winds make for favorable trajs to bring lake effect clouds and
precipitation into north-central WI and with min temperatures forecast to be in the middle
30s...have gone ahead and mentioned the possibility of a rain/snow
mix over parts of north-central WI for late Thursday night. Away from the lake
effect clouds/pcpn...the rest of NE WI should see mostly clear to
partly cloudy skies with cool temperatures as readings dip into the middle
to upper 30s central/far NE WI...around 40 degrees east-central WI and lower 40s
Lakeside. The lake effect potential over north-central WI will carry over
into Friday as colder air aloft continues to settle over the Great Lakes.
800 mb temperatures over Western Lake Superior to be in the -6 to -8c range which
would bring Delta-T values into the upper teens. Anticipate a
rain/snow mix chance to persist over the Northwoods through at least
midday...but tend to weaken Friday afternoon as an area of hi pressure
builds toward WI. The remainder of NE WI to stay and
blustery with maximum temperatures 5 to 10 degrees below normal and sustained northwest
winds at 10 to 20 miles per hour with higher gusts.

This area of hi pressure pushes east-southeast into the Great Lakes for the
first half of the weekend and bring quiet...but cool conditions to
the forecast area. If boundary layer winds can subside fast enough Friday
night...E-cntrl WI could see its first freeze of the fall season
(lakeside locations would see just frost). Sat's maximum temperatures will be
similar to Friday with lower to middle 40s north-central WI to near 50 degrees
east-central WI. After another rather cold night with mins in the 20s to
lower 30s...Sunday looks to be a rather nice day as the surface hi moves
east and a return flow sets up over WI. Winds shift to the SW and
warm air advection takes over as 800 mb temperatures climb to around +5c by 00z Monday. This
should allow maximum temperatures to reach the lower to middle 50s throughout the
entire forecast area.

The forecast for early next week becomes more complicated as the
prevailing SW winds begin to tap Gulf moisture and isen lift
increases over WI. Hard to determine at this juncture the strength
of the isen lift or if an approaching cold front will get close enough to
WI to aid in the development of shower activity. For now... have
followed the consensus solution which brings small chance probability of precipitation to the
area on Monday. Temperatures will continue to warm with maxes on Monday ranging from
55 to 60 degrees.

Aviation...for 18z taf issuance
issued at 1205 PM CDT Tuesday Oct 13 2015

MVFR ceilings will likely continue through middle-afternoon at
most locations based on statistical guidance. Breaks in the
overcast are more likely over eastern Wisconsin per satellite
imagery. Though light rain and drizzle should end over north-c WI this
afternoon...clouds will likely remain broken into the evening hours.
Then clearing should take place from west to east overnight. VFR
conditions will prevail on Wednesday.

Grb watches/warnings/advisories...


short term.....Skowronski
long term......kallas

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