Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 262345
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
645 PM CDT Wed Apr 26 2017

Updated aviation portion for 00Z TAF issuance
and new information added to update section

.UPDATE...
Issued at 629 PM CDT Wed Apr 26 2017

Watching a fairly consistent trend of the meso-models wrapping
pcpn farther back to the west late tonight into Thursday morning.
If this is correct, and if temperature forecasts reach current
forecast values or get a little cooler, we may need to consider
winter weather headlines for a mix of freezing rain, sleet and
snow in our far northwest counties. Will monitor this over the
next hour or two.

&&

.SHORT TERM...Tonight and Thursday
Issued at 235 PM CDT Wed Apr 26 2017

The latest rap analysis and satellite/radar imagery show low
pressure over northeast Wisconsin early this afternoon, with a
trailing cold front extending south into Missouri.  Widespread rain
is about to exit far northern WI ahead of the low, and a significant
break exists between this area of rain, and the next area, which is
surging northeast over southern Illinois.  This secondary area is
ahead of another surface wave positioned over southern Missouri.
Looking to the northwest, colder air lies just upstream, with
temperatures in the upper 20s to lower 30s from the Arrowhead of
Minnesota to Ironwood.  Several obs are reporting snow in these
areas.  Forecast concerns revolve around precip trends with the
arrival of the secondary low tonight, and potential for wintry
precip over north-central WI as colder air filters in behind this
low.

Tonight...A complicated forecast.  Low pressure over northeast
Wisconsin will depart over eastern Lake Superior this evening.
Between this system and the arrival of a secondary low, will likely
see a lull in the widespread precipitation, though some occasional
drizzle will likely occur over central and north-central Wisconsin.
The secondary low will move towards southern Lake Michigan late
tonight and bring another swath of widespread precipitation to the
area.  The heaviest rain remains forecast for eastern WI, where
upwards of a half inch of rain could fall.  Amounts will be
considerably less over central and north-central where north winds
behind the low will draw in colder air from northwest Wisconsin and
northern Minnesota.  Because of these colder temps, potential
remains for wintry precipitation, mainly over Vilas and western
Oneida/Lincoln counties.  A small window may start to open late
tonight, when temperatures cool at the surface and more widespread
precipitation arrives, for accumulating wintry precip in the form of
snow/sleet/and freezing rain.  Think any accumulations will mainly
be confined to grassy and elevated surfaces, though cannot rule out
patches of minor accumulations on roadways in the heavier precip
rates.  The potential for slippery stretches on roads will likely
end by 8am as road temps warm with solar insolation.  Because of the
narrow time window, and uncertainty revolving around temps/precip
coverage, will continue to highlight the threat of slippery roads in
a SPS.

Thursday...Low pressure will continue to lift north over Lake
Michigan and into Lake Superior.  Widespread precip will likely be
lifting north on the western flank of the low across much of the
area during the morning, with some wintry precip over north-central
WI.  Precip will exit during the afternoon, but mostly cloudy
conditions will linger.  Because of the precip and cold advection,
temps will only rise into the middle 30s in the north to middle 40s
near the Lake.

.LONG TERM...Thursday Night Through Wednesday
Issued at 235 PM CDT Wed Apr 26 2017

The first storm will continue to move away from the region
Thursday night. Some wrap around moisture lingering across
the far north to support small chances of precipitation
(mainly over Vilas County) Thursday night. Left Friday morning
dry across the north, but could not rule out a few flurries.
There was a change in the forecast for Friday afternoon into
Friday night as system passes to the south. Several models
depicting light rain across east-central Wisconsin, and as far
north as Green Bay. Have added a chance of rain to account for
this feature. High pressure will then dominate the weather
pattern Saturday into Saturday evening.

Next system approaching from the south a little quicker than
previous runs. This would support more snow at the onset,
especially across the north late Saturday night into Sunday
morning. Do think the heaviest precipitation will arrive by
mid morning across the north, thus any accumulation would
be on the light side and not cause too many impacts. Will need
to see if the system speeds up over the next day to see if
more snow accumulation would need to be added to the forecast.
It appears Sunday is going to be a washout with periods of
rain, mixed with snow across the north during the morning.
System will move across the region Sunday night into Monday
morning. Dry slot may move across our southeast counties
after midnight. Will also need to monitor thunder prospects
across our southeastern counties as well. Do not have thunder in
the forecast at this time since it is still pretty far out.
Across the north, light snow is expected at times with some
snow accumulation possible Sunday night into Monday morning.

Any lingering precipitation comes to an Tuesday with dry
conditions expected on Wednesday as high pressure dominates
the weather pattern. Below normal temperatures are expected
through much of the period. In matter of fact, the latest
numerical guidance indicated no 60s or 70s during the next
seven days at Green Bay.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 629 PM CDT Wed Apr 26 2017

Widespread IFR/LIFR conditions covered most of the north central,
central and far northeast WI early this evening, with MVFR/VFR
ceilings occurring ahead of a cold front in eastern WI. The cold
front will shift east, and should reach the lakeshore by around
06z. After the front moves through, ceilings will drop off in
eastern WI. Another area of significant precipitation will arrive
overnight into Thursday morning, and models are indicating that it
will develop farther to the west than previously expected. While
most of the region will see rain, our northwest counties,
including the RHI TAF site, will likely see a mix of freezing
rain, sleet and snow late tonight into Thursday morning, as
temperatures drop slightly below freezing. Some improvement to
ceilings and visibilities are likely on Thursday afternoon as the
precipitation pulls out to the northeast.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE.........Kieckbusch
SHORT TERM.....MPC
LONG TERM......Eckberg
AVIATION.......Kieckbusch



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