Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 080336
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1036 PM CDT Fri May 7 2021

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 239 PM CDT Fri May 7 2021

It did not take long for skies to cloud over this morning due to
cold air filtering in around 850mb and a mid-level shortwave
brushing across northeast WI. Scattered rain showers have also
been occurring across northeast and east- central WI which
occasionally produced some small graupel as well.

Tonight...Showers and clouds will quickly begin to dissipate early
this evening with the loss of daytime heating at the surface and
as the shortwave exits the state. High pressure builds in at the
surface which will lead to several hours of light to calm winds
overnight. As a result, temperatures will fall to near or several
degrees below freezing. Forecast lows range from the low to
middle 20s in north- central WI, to the upper 20s in central WI,
and the low 30s across the Fox Valley and east- central WI.
Therefore, issued a Freeze Warning for the entire forecast area
from midnight to 8AM. Anyone with cold sensitive outdoor plants
should take the necessary steps to protect the plants tonight, and
for the next several nights as similar low temps are expected.

Saturday...After a seasonably chilly and sunny morning,
temperatures will be a little warmer tomorrow, reaching the mid to
upper 50s away from Lake Michigan. This is about 10 degrees below
normal for early May. Clouds will increase during the afternoon,
first from destabilization, and then some high clouds will move in
from a weather system moving across the central Plains. A few
light showers or sprinkles are possible in far northeast WI, but
will not be as numerous as today.

.LONG TERM...Saturday Night Through Friday
Issued at 239 PM CDT Fri May 7 2021

The main issue in the extended will be the continued below normal
temperature trend through the first half of the work week, with
frost/freeze expected overnight and early in the mornings. A trend
toward normal or above normal can be expected for the end of next
week.

Saturday night and Sunday: A low pressure system is progged to shift
from eastern KS Saturday evening into the Ohio Valley Sunday
afternoon. The more concentrated moisture and forcing is expected to
remain south of the area through this time period; however, cloud
cover is expected to increase throughout the day Sunday. Aloft, an
upper-level closed low is expected to drift across central Canada
and linger near James Bay. This will allow intermittent shortwaves to
pass through northeast Wisconsin. The main impact will be an
increase in afternoon cloud cover and perhaps an isolated shower or
sprinkles. The air in the lower levels of the atmosphere looks to be
fairly dry for Sunday afternoon, so went with a dry forecast at this
point. Overnight lows are expected to range from the upper 20s to
around 30 near the UP/WI border to the mid and upper 30s across
central and east-central WI. This will likely require another
frost/freeze headline late Saturday night into Sunday morning. High
temperatures are expected to be in the 50s.

Sunday night through Monday night: The aforementioned upper trough
will drift very slowly off to the east during this time period. This
will keep a trough axis across much of the area. Again, not
expecting much precipitation; however, cloud cover will likely
increase during the afternoon hours and diminish overnight. This
will lead to lows in the upper 20s to mid 30s, again leading to
frost/freeze headline issuances. Highs will be in the 50s.

Rest of the extended: A surface high pressure system and upper-level
ridging is expected to slide across the area for much of this time
period; however, there are some model agreement issues for Wednesday
into Thursday as a shortwave is expected to pass through the area.
The GFS has more moisture with this feature, while the EC continues
to keep dry air in place. At this point, have decided to stick with
a consensus of the models, giving increasing temperatures and
increasing chance for rain. Temperatures are expected to warm to
near or above normal by the end of the work week. Upper 60s to
around 70 looks possible by Thursday and Friday.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1035 PM CDT Fri May 7 2021

High based cumulus clouds will dissipate over eastern
Wisconsin by shortly after midnight with clear skies expected
overnight. Pilots may need to clear frost from aircraft parked
outdoors if they are departing before sunrise Saturday.

Saturday will be sunny to start with scattered to broken cumulus
clouds with bases between 5000 and 8000 feet in the afternoon.
Some virga is possible from these clouds.

Skies should clear Saturday evening, with good flying weather
Sunday.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 8 AM CDT Saturday for WIZ005-010>013-
018>022-030-031-035>040-045-048>050-073-074.
&&

$$

SHORT TERM.....KLJ
LONG TERM......Cooley
AVIATION.......RDM


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