Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 271715

Area Forecast Discussion
National Weather Service Green Bay WI
1215 PM CDT Mon Mar 27 2017

Updated aviation portion for 18Z TAF issuance

Issued at 357 AM CDT Mon Mar 27 2017

Quiet weather for a few days, then the chance for mixed wintry
precipitation will return for the latter part of the work week.

Split flow is in place across North America, and will remain so
through the entire 7 day forecast period. The forecast area will
primarily be under the influence of the southern stream, at least
until late in the period. A series of upper-level cyclones
embedded within the southern stream will slowly cross the country,
with precipitation chances tied to those. Precipitation totals
for the period will probably range above normal across the
southern portion of the forecast area to below normal across the
north. Temperatures will probably not stray too far from seasonal
normals, though any days with widespread precipitation will  be
on the chilly side for late March.

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 357 AM CDT Mon Mar 27 2017

The initial upper system in the newly evolved southern stream was
finally pulling away from the area. But plenty of moisture will
linger in its wake, and a weak mid-level shortwave will cross the
area today. A couple small clusters of showers had developed to
the west with that feature. Models generated scattered light
precipitation over the area today, with what focus there was
generally over north-central Wisconsin this morning. Opted to keep
low chance PoPs across the area to account for this.

A few showers or sprinkles could linger into this evening, but
the risk of that seemed too low to add to the forecast so kept it dry
at this point. The main issue tonight is to what extent clouds
clear from the north. Given pretty extensive low cloud deck to the
N/NE this morning, opted for a little slower clearing trend,
especially across the southern part of the forecast area.
Sharpened the north/south gradient in overnight lows to account
for the cloud differential across the area. Will need to watch
areas that clear as fog/stratus could easily redevelop in the
light low-level flow regime.

Northeast flow will probably strengthen on Tuesday as a Canadian
anticyclone builds toward Ontario. That will help scour out the
clouds, which should allow temperatures to rebound to a little
above normal. The exception will be areas near the lake and bay,
where the flow off the cold water will hold readings back in the

.LONG TERM...Tuesday Night Through Sunday
Issued at 357 AM CDT Mon Mar 27 2017

Expect dry weather at the start of this forecast period with
surface high pressure and an upper ridge across the region.

An upper trough that was over the eastern Pacific is currently
moving onshore and a closed 500 mb low was forecast to develop by
the time the trough reaches the southwest CONUS during the early
part of the week. 00Z models continued to show differences in
their handling of this feature and an associated surface low. The
GFS solution is closer to the ECMWF and Canadian that it was 24
hours ago, but there were still noticeable differences.
Precipitation chances return as a surface low approaches the
region and passes southeast of Wisconsin. The GFS only had QPF
reaching about the southern half of the forecast area while the
ECMWF and Canadian had at least some measurable precipitation
across the entire area by the end of the day on Thursday. The
00Z/26 GFS had Wisconsin completely dry, so it has shifted north
quite a distance and this makes the ECMWF and Canadian solutions
appear to be more likely.

There is a chance for light snow in central Wisconsin after 06Z
Thursday. Snow should mix with, and then change to, rain as
temperatures warm on Thursday. There could be a few tenths of an
inch of snow accumulation by the time it changes to rain, but that
should quickly melt. Rain chances then spread across the rest of
the forecast area by 00Z Friday. A change back to snow is
expected again Thursday night. Precipitation chances start to
decrease after 06Z Friday and slowly come to an end from west to
east. Dry conditions are expected across the entire area by 06Z
Saturday as the surface low continues to move away from Wisconsin.
Precipitation type should continue the pattern of rain during the
day, snow at night, and a transition during the evening and early

The forecast is dry from 06Z Saturday through 18Z Sunday with
surface high pressure somewhere in the vicinity of the forecast
area. Models differences were many by Sunday so the model blend
was left as it was, with only slight chances for rain Sunday

Highs start out near normal, then below normal daytime
temperatures return for Thursday and Friday with the clouds and
rain. Weekend highs should be warmer than normal.

.AVIATION...for 18Z TAF Issuance
Issued at 1124 AM CDT Mon Mar 27 2017

Ceilings should continue to slowly rise this afternoon with
daytime heating. A few spotty showers will pass over north-central
WI this afternoon. Confidence in the forecast for tonight remains
low, as there is uncertainty as to how much clearing will work
down from the north. Then if clearing occurs, there is further
uncertainty in whether or not FG/ST will redevelop. Kept some
continuity with IFR fog/cigs in the north, though in reality it
could end up being an all (VLIFR cigs/vsbys) or nothing (no clouds
or fog) situation.




SHORT TERM.....Skowronski
AVIATION.......MPC is the U.S. government's official web portal to all federal, state and local government web resources and services.