Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 252016

Area Forecast Discussion
National Weather Service Green Bay WI
316 PM CDT Wed Apr 25 2018

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Thursday
Issued at 315 PM CDT Wed Apr 25 2018

Clear skies and light winds will allow temperatures
to fall into the 20s and 30s overnight, with the coldest
temperatures where there is snow cover. Clouds will increase
Thursday afternoon as a cold front approaches. There is not much
moisture available, so expect just scattered showers in the
afternoon. Temperatures will be well above normal.

.LONG TERM...Thursday Night Through Wednesday
Issued at 315 PM CDT Wed Apr 25 2018

Post-frontal rain shower activity, aided by a mid-upper level
trough, will be coming to an end across the area Thursday
evening. The cold air should trail the precip enough to limit most
mixing, but thermal profiles cool just enough that the precip
could end as a little snow, mainly over the north. No accumulation
is expected.

As the upper trough digs over the Great Lakes, another more potent
shortwave will approach the area within the northwest flow early
on Friday. The surface reflection of these features is a clipper-
like low pressure system. The area will also reside in a
favorable left front quad of a 100+ knot jet. These in combination
with steepening low and mid level will begin to spread precip
into the area. With low temps forecast to drop into the upper 20s
for much of north-central WI early Friday morning, if any precip
gets going that early, it could start off as a rain/snow mix or
even all snow. As temps warm, precip should change to all rain
for most locations. However, concern is growing (especially across
central and northern WI) that thermal profiles are getting closer
and closer to an all snow scenario, at least during periods of
heavier precip. The NAM NEST shows this scenario, with a band of
snow on the northern side of the surface low, bringing an inch or
two of snow. It is the end of April and the sun angle is strong,
so will hope the "all snow" scenario doesn`t play out. However,
did increase snow totals a little (mainly on grassy surfaces).

In addition to the snow threat, steep low-mid level lapse rates
(6-8 C/KM) will bring the chance for some thunder. Any convection
could produce small hail as wet-bulb zero heights remain low.
Brief gusty winds will also be possible with any of the stronger
showers or storms, especially across central and east central WI
where soundings still show an inverted V signature for a period
of time. Winds aloft are not too strong, so gusts between 30-40
mph would be expected. Will continue to highlight these threats in
the HWO.

Any lingering precip will end Friday evening as the shortwave and
upper trough exit the area. Then, models still advertising a
significant pattern change this weekend into next week. The strong
southwest flow will result in very warm temps with highs in the
70s expected early next week. The chances for showers and storms
will also be on the increase early next week, but timing is hard
to pin down at this point. This type of setup needs to be
monitored for possible heavy rain (additional flooding?) and
strong to possibly severe weather. Stay tuned!.

.AVIATION...for 18Z TAF Issuance
Issued at 1250 PM CDT Wed Apr 25 2018

Clear skies and light winds are expected through
midday Thursday. An approaching cold front will bring the chance
of showers and MVFR conditions Thursday afternoon and evening.



LONG TERM......Bersch
AVIATION.......RDM is the U.S. government's official web portal to all federal, state and local government web resources and services.