Forecast Discussion for GRB NWS Office
FXUS63 KGRB 160005

Area Forecast Discussion
National Weather Service Green Bay WI
605 PM CST Sun Dec 15 2019

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 230 PM CST Sun Dec 15 2019

Fairly quiet weather expected through the short-term portion of the

Surface high pressure will remain in control through much of the
short-term part of the forecast. The two notable features will be a
shortwave passing just south of the area tonight and a cold front
brushing far northern Wisconsin late tonight into Monday morning.
The main concern with these features will be increasing cloud cover
through this time period. Low-level moisture is very limited with
most of the moisture expected to be confined to 875-800mb layer.
Limited forcing along with the shallow moisture will limit any
potential for light snow. It is not completely out of the question
that a few flurries may occur, especially close to the shortwave
passing south of the area tonight.

Perhaps the biggest impact from the cloud cover will be on the
overnight low temperatures. A fairly extensive shield of cloud
cover extends from western WI across much of the northern Plains.
This added cloud cover, moving across the area tonight, will
likely keep temperatures from dropping to the lowest guidance;
however, there are some decent breaks in the cloud cover sliding
across northern MN. If the clouds clear, even for a brief period
of time, temperatures will likely drop quickly. Overnight lows are
forecast to drop to around 0 or just below over central/north-
central WI to the single digits to low teens above zero over the
east-central and far northeast WI. High temperatures are expected
to be in the teens and 20s for Monday.

.LONG TERM...Monday Night Through Sunday
Issued at 230 PM CST Sun Dec 15 2019

Surface-based low pressure over the Plains States will continue to
strengthen and expand east. Precipitation associated with this
system will stay south and east of our area. Temperatures will
stay cold in the western Great Lakes region for the next few days
as the system integrates with broader low pressure in Canada and
northerly winds persist in our region as a result. However,
another low will move east out of the Rockies on Thursday and
temperatures will begin to moderate as southerly winds develop
ahead of the low, drawing warmer air into the northern Midwest.
At this time, it appears the bulk of precipitation associated
with this later-week system should stay south of our area.

.AVIATION...for 00Z TAF Issuance
Issued at 601 PM CST Sun Dec 15 2019

The main aviation forecast issue is the potential for low clouds
advancing into the region to produce MVFR conditions. MVFR
ceilings were generally back in far NW WI and MN, but spreading
east. They will likely spread into the RHI area during the mid-
late evening, and probably reach into central Wisconsin later in
the night. Kept them out of E-C WI with the 00Z TAF package, but
will reevaluate that later this evening. Some low-end LLWS may
brush across the north late tonight.



SHORT TERM.....Cooley

NWS GRB Office Area Forecast Discussion