Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 162027

Area Forecast Discussion
National Weather Service Green Bay WI
327 PM CDT SUN OCT 16 2016

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Monday
Issued at 327 PM CDT Sun Oct 16 2016

Precipitation trends and potential for severe storms are the main
concerns during this part of the forecast.

A warm front is forecast to move into the area from the south, strong
warm advection will develop as 850mb winds increase into the 35
to 40 knot range, and a mid level short wave will move into the
region. These factors will combine to bring a chance for showers
and thunderstorms to the forecast area starting late this evening.
12Z NAM and GFS showed MU CAPE values in excess of 1000 j/kg
across at least the southwest half of the forecast area with wet
bulb zero heights near or below 10 kft. SPC day 1 convective
outlook had the forecast area in a marginal risk through 12Z
Monday, mainly focusing on hail.

A surface low moving along the frontal boundary will combine with
an approaching mid level short to keep the chance for
thunderstorms going through Monday but temperatures should still
reach highs in the mid 60s to mid 70s.

.LONG TERM...Monday Night Through Sunday
Issued at 327 PM CDT Sun Oct 16 2016

Impressive dynamics for this time of the year which continue into
Monday night will be the primary issue with this forecast period.

A marginal risk of severe storms over the northwest half of
Wisconsin Monday into Monday night or day 2 is well deserved. For
starters, 130 knot upper jet is progged to be positioned over
northern Wisconsin in addition to a frontal boundary. The
unseasonably warm moist and unstable air mass for this time of the
year will be working with a deep sheared environment. Mu capes
1000 to 1500 J/kg at the onset Monday evening before subsiding
from north to south overnight. SB capes slightly lower but severe
potential likely to be depend on the mid level cap eroding monday
afternoon. Still even the elevated convection could be capable of
producing large hail. A short wave trough with 850 low will track
over northern Wisconsin Monday night for a focus of heavy rain
across the north in addition to the severe weather potential.

Most of the precipitation will depart to the northeast with the
short wave Tuesday morning while the surface and 850 mb cold
front slides south over the area through Tuesday. This frontal
passage will lead to the start of a cooling trend.

For the rest of the week, an overall drier period with a
continued cooling trend as a series of short wave troughs with
reinforcing cold fronts will track over the areas. Precipitation
chances will be very spotty in the drier airmass, but the -4 C
850 MB air mass by late in the week may produce isolated light
diurnal pcpn.  Obviously timing differences can be expected with
these short wave troughs in the fairly fast northwest to west
flow. Compared to 24 hours ago, do note progs have backed off on
the deep upper trough just east of the area by the end of the

.AVIATION...for 18Z TAF Issuance
Issued at 102 PM CDT Sun Oct 16 2016

VFR conditions will prevail across the forecast area through the
end of the day. Showers and thunderstorms are expected to move
into central and north central Wisconsin late this evening and
continue to the east overnight, as a warm front pushes northeast
across the state. IFR with scattered MVFR conditions should
prevail across the area overnight in low clouds and fog. Showers
and storms should end by morning, but it may take a while to get
rid of the fog and low clouds.



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