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831
FXUS63 KGRB 191709
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1209 PM CDT Mon Apr 19 2021

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 419 AM CDT Mon Apr 19 2021

A cold front was moving through eastern WI early this morning. The
front, in concert with a short-wave trough and LFQ of an upper
level jet, was producing a band of rain showers. Radar showed the
showers quickly exiting the region. Lake-enhancement due to cool
northwest flow off Lake Superior was also producing light snow
showers or mixed precipitation in north central WI.

Expect abundant cloud cover to linger over the forecast area
today, as an upper level trough remains over the western Great
Lakes. Lake-enhanced snow showers should persist over Vilas
County, with isolated diurnally-driven rain or snow showers
redeveloping elsewhere during the afternoon. Significantly cooler
conditions are anticipated, with highs in the middle 30s to
middle 40s. Blustery northwest winds will gust to around 25 mph,
before tapering off early in the evening.

Lingering showers should taper off this evening, with skies
becoming partly cloudy overnight. Low temperatures are expected to
drop into the upper teens and 20s.

On Tuesday, expecting somewhat of a repeat performance (minus the
gusty winds), with mostly cloudy skies, cool temperatures and
isolated afternoon rain or snow showers. Highs will be in the
middle 30s to middle 40s.

.LONG TERM...Tuesday Night Through Sunday
Issued at 419 AM CDT Mon Apr 19 2021

No major systems forecast to impact the area through the weekend.
Upper trough will provide for north/northwest flow and cloudy/cool
conditions through mid-week then a more zonal flow sets up
bringing in a warmer Pacific airmass for the end of the week.
Still some questions on how that pattern will play out late this
week and into the weekend, impacting precip chances and temps.

Tuesday night into Wednesday...upper level trough will be firmly
planted over the Great Lakes. Some breaks are possible in the
overcast, but mostly cloudy skies look to prevail most of the
time. The cyclonic flow, cold air aloft, lingering moisture, and a
weak shortwave or two, could kick off some light/spotty rain or
snow shower or sprinkle/flurry activity, especially on Wednesday.
Some disagreement in just how much low-level moisture will remain,
which leads to questions if there is enough moisture/lift to
squeeze out some precip. GFS is the most bullish, showing up to a
tenth of QPF over parts of central WI. Won`t go that far, but
will add slight chance PoPs, as the combination of available
moisture, upper trough overhead, cold air aloft, steep low level
lapse rates and a weak shortwave should provide enough support for
at least some spotty precip activity. Well below normal temps
will continue as it will be another cold/chilly night, with lows
in the teens and 20s. If skies clear out more than anticipated,
the typical cold spots could drop closer to 10 degrees. Highs look
to be similar to Tuesday, but perhaps slightly warmer, with most
spots in the 40s.

Thursday into Friday...the upper trough will continue to shift
toward the East Coast, finally loosening its grip on the area and
allowing ridging to build into the Great Lakes. It looks to be
dry from Thursday into Friday morning, then models are signaling
some WAA precip possibly spreading into the area later on Friday,
along with some possible precip associated with an approaching
trough and cold front from the west. Model blend paints some low-
end PoPs starting Friday afternoon and can`t really argue with
that at this point. As the flow turns more zonal, a push of
Pacific air will spread into the area. Highs look to jump 10-15
degrees compared to Wednesday, with most spots seeing highs in the
50s to near 60. Depending on cloud cover and possible precip, we
could see some spots climb over the 60 degree mark.

Saturday and Sunday...the forecast gets more and more murky as
models diverge on how the overall pattern will play out. Timing
differences are a plenty regarding the frontal boundary, how
chilly the air is behind it and how fast the WAA occur ahead of
another system to our west occurs. Will continue to stick with
the model blend for now, which keeps chance PoPs through Saturday
but keeps Sunday dry and temps near or slightly below normal.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1203 PM CDT Mon Apr 19 2021

Scattered snow showers will continue across the far north into
this evening with isolated rain or snow showers over the remainder
of the area this afternoon. Most CIGS will be in the VFR category
with MVFR CIGS at times in the rain or snow showers. Clouds will
be on the decrease tonight with VFR conditions through Tuesday
afternoon. Gusty northwest winds may gusts to around 30 knots this
afternoon will quickly subside around and just after sunset.
Northwest winds are expected on Tuesday, although could swing
around to the northeast or east during the afternoon at
KGRB/KATW/KMTW.

&&

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

$$

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