Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 191949
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
249 PM CDT Sun Mar 19 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Monday
Issued at 249 PM CDT Sun Mar 19 2017

Partly to mostly cloudy skies prevailed across the region this
afternoon. Temperatures at most locations will be in the upper 30s
to middle 40s. A weak cold front is expected to move across the
region later tonight. This front could trigger some shower
and isolated thunderstorm activity ahead of the front. Will
continue the mention of thunder in the forecast for the far
north late this afternoon and across much of the area this
evening. A few showers will linger across the east after midnight.

For Monday, clouds will be on the decrease from north to south. It
will be warmer on Monday behind the front due to decreasing cloud
cover and a warmer start to the day. Took a blend of guidance
values for lows tonight and highs on Monday.

.LONG TERM...Monday Night Through Sunday
Issued at 249 PM CDT Sun Mar 19 2017

Big forecast concern will be how the the system at the end of the
week plays out with many questions to be answered. Otherwise,
fairly quiet weather is expected with high pressure in control,
with much cooler air arriving Tuesday and Wednesday.

Monday night through Wednesday...secondary cold front sweeps
across the area Monday night, but looks to be lacking moisture to
produce any precip. Behind the front, lake effect snow will begin
off of Lake Superior as 850mb temps drop to around -16C providing
for favorable delta T`s. However, dry air and only a short period
of NW winds will keep the lake effect activity pretty short-lived
and light with only minor accumulations possible across Vilas Co.
from overnight Monday into Tuesday evening. The rest of the area
looks to be dry under partly cloudy to mostly clear skies.
Tuesday night will be the coldest as the high pressure system
moves into the Great Lakes bringing mostly clear skies. Single
digits low temps are expected over the north and between 10 to 20
elsewhere. Wednesday will be the coldest day of the next several
and the central of the high moves overhead. 850mb temps of -9C to
-13C should only allow highs to climb into the 30s for most
locations.

Warm air advection begins to ramp up Wednesday night into
Thursday, with 850mb temps climbing around 10C. Best moisture will
be located west of the area, so see the majority of the precip to
stay across western WI, but could see some light snow make it into
central and northern WI overnight Wednesday. Dry air at the lower
levels should help keep this activity from making it into eastern
WI.

The main event arrives at the end of the week, with still some
model differences with how the system will play out, as one would
expect with a split flow pattern. However, models are trended
toward a prolonged precip event starting Thursday night and
continuing through Saturday morning with no/little phasing and
the southern stream system taking the lead role. There is still a
chance models could trend back toward more phasing and a more
wrapped up system, which would bring more of a wintry mix to our
area (assuming the low tracks far enough south to bring in the
colder air). As it stands now, not much snow/wintry mix is
expected across the Fox Valley as temp profiles look warm enough
for rain through most of the event. Across northern WI, the models
differ on how much cold air will reside on the northern edge of
the precip. GFS would have mainly rain, but the Canadian is nearly
5C colder and would have a wintry mix Thursday night into Friday
morning with temps in the upper 20s and lower 30s. The ECMWF is in
the middle. Will trend the forecast a little warmer and remove
some of the mix over the central WI and confine it to northern WI.
The precip looks to change to all rain for the entire area on
Friday as temps climb into the 40s (north) and 50s (south), then a
transition back to a little light snow on the back side of the
system overnight Friday into Saturday. Did not add any thunder at
this point, but some may need to be added in the warm sector on
Friday.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1208 PM CDT Sun Mar 19 2017

MVFR CIGS continued across portions of east-central and northeast
Wisconsin early this afternoon. These low clouds will linger
through much of the afternoon. Meanwhile, a weak cold front will
move across the region tonight, bringing a small chance of showers
and possibly a thunderstorm. The chances for showers/storm moving
across an airport site is very low, thus only went with VCSH in
the 18z tafs. Some mvfr cigs and fog are possible behind the
cold front late tonight into early Monday morning.
&&

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

$$

SHORT TERM.....Eckberg
LONG TERM......Bersch
AVIATION.......Eckberg


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