548
FXUS63 KGRB 150335
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1035 PM CDT Tue May 14 2024

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Areas of frost are possible over north-central and far
  northeast Wisconsin tonight.

- Relative humidity is expected to drop into the 25 to 35 percent
  range away from the bay and lake Wednesday afternoon which may
  cause increased fire potential.

- A couple of thunderstorms will be possible in the area Thursday
  afternoon. Additional chances for rain and possibly thunder will
  be in the region Friday afternoon, Saturday night, and Sunday.

&&

.DISCUSSION...
Issued at 250 PM CDT Tue May 14 2024

Short Term...Tonight and Wednesday

Main forecast challenge to be on temperatures for tonight as skies
clear and winds diminish.

The 19Z MSAS surface analysis showed a ridge of high pressure that
extended from northern Ontario southwest into the Upper MS Valley.
A triplicate of weak low pressure areas were situated over
western ND, southwest SD and western NE. Visible satellite
indicated a band of clouds over the southern Great Lakes
associated with a system over the mid-MS Valley and another band
of clouds associated with the low pressure areas over the northern
Plains.

This ridge of high pressure will slowly shift east and move into
the western Great Lakes tonight. Other than some high clouds
drifting overhead at times, mostly clear skies and light winds can
be expected tonight. Due to the relatively dry air mass in place,
temperatures are forecast to quickly drop later tonight into the
lower to middle 30s across the north and prompt the need for a
Frost Advisory. Central and east-central WI should stay in the
lower to middle 40s and be safe from any frost.

This ridge to continue slowly moving east on Wednesday and remain
our main weather feature through the day. Low pressure is expected
to merge over the northern Plains and join up with a mid-level
shortwave trough. Some middle and high clouds may push east ahead
of these systems and reach central WI Wednesday afternoon. Max
temperatures for Wednesday to range from around 60 degrees near
Lake MI, upper 60s to around 70 degrees across central WI.

Long Term...Wednesday Night Through Tuesday

Active weather will work its way back into the forecast during the
extended period, with several chances for some rain and/or a few
storms from the end of this work week through the weekend.

Thursday...A fast moving upper shortwave will work its way into
the region early on Thursday, bringing showers into the area from
west to east. Moisture will be relatively limited early in the
day, but precipitable water values do increase later in the day as
the system continues to occlude. Instability values will increase
in the afternoon but remain modest with around 300-500 J/kg CAPE
across the eastern portions of the area. This could support some
thunder in the afternoon, but severe weather is not expected.
Overall, rainfall amounts will likely be a widespread couple of
tenths, but higher amounts approaching a half inch will be
possible with any thunderstorms in eastern Wisconsin.

Friday...Behind the system from Thursday, the general trend for
Friday has been towards a drier forecast. The more unsettled
airmass to our south could largely remain south during the day
while the next clipper in Canada will yet remain west. As a
result, Friday does see the potential to largely remain dry.
Maintained low pops for now however, as soundings do support the
potential for some meager instability, especially if temperatures
come up another few degrees. This could ultimately still result in
a few showers in the area, even if most of the region remains dry
and the larger system remain out of the area.

Rest of the forecast...The next chance for precipitation will be a
relatively fast moving system over the weekend. Many of the
details of this system remain unclear, with timing ranging from
late Saturday to early Sunday. Although the details may vary, none
of the current scenarios for this system include strong or severe
storms, so the main thing to look for will be changes in
precipitation amounts.

Outside of rain, temperatures will be on the rise through the
weekend, with highs in the 80s both Saturday and Sunday. Then,
temperatures will begin to decrease again next week, with highs
back in the 70s early next week.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1032 PM CDT Tue May 14 2024

VFR conditions will prevail through Wednesday evening. Frost is
possible overnight across far north-central and far northeast
Wisconsin. On Wednesday, wind gusts to around 15 knots
are possible from 16z Wed to 01z Thu. The next chance for
showers and thunderstorms arrives early Thursday morning, then
chance of rain will continue through the day Thursday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 7 AM CDT Wednesday for WIZ005-010>013-018-
019-021.
&&

$$

DISCUSSION.....Kallas/Uhlmann
AVIATION.......Eckberg