577
FXUS63 KGRB 252339
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
639 PM CDT Sat May 25 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Rain is likely Sunday afternoon through Sunday night. Non
  severe thunderstorms are possible south of a Wausau to Green Bay
  line. Up to an inch of rain is likely west of a Niagara to
  Waupaca line, with 1 to 2 inches expected in the Fox Valley and
  lakeshore counties. Some minor flooding of streets and small
  stream is possible.

- A few rivers over central and eastern Wisconsin could surpass
  minor flood stage early next week.

- Patchy frost is possible Wednesday night through Thursday
  morning across the far north.

&&

.DISCUSSION...
Issued at 255 PM CDT Sat May 25 2024

Short Term...Tonight and Sunday

After a beautiful sunny day today, clouds will increase tonight
as an upper level trough and a low pressure system at ground level
approach from the Southern Plains. The clouds will keep
temperatures a few degrees above normal overnight.

Sunday morning should be dry in most places, but rain will arrive
from southwest to northeast during the day, with rain falling all
across the area by late afternoon. Some thunderstorms are possible
south of a Green Bay to Wausau line, but not severe. Locally heavy
rain is likely especially across east central and far Northeast
Wisconsin late Sunday afternoon and night, as the surface low
strengthens. Computer models suggest that an inch or two of rain
may fall east of a Niagara to Waupaca line, with less to the west.
That amount of rain could produce street flooding in urban areas
and bring small streams to bankfull. High temperatures will be
early in the day Sunday, as they will fall after the rain arrives.

Long Term...Sunday Night Through Saturday

The extended sees the current active pattern quieting down toward
mid-week following a couple rounds of precip Sunday evening
through Tuesday. Periods of moderate to heavy rain will be
possible during this time, especially across east-central and
northeast Wisconsin. The remainder of the extended then looks to
be mostly dry as an omega block sets up across the central CONUS.
As a result, temperatures will begin a gradual incline through the
end of the week.

Sunday evening through Tuesday precip chances... Mid-level shortwave
energy will spin up a surface low over the central Plains before
tracking up into the Great Lakes Monday morning. Warm air
advection precip is expected to be ongoing across east-central and
northeast Wisconsin Sunday evening before departing overnight.
Most convective elements (moisture, shear, instability) look to be
trapped in the warm sector to our south, thus not too impressed
with storm chances making it this far north. Overall thinking is
that a widespread inch of QPF is possible across the forecast area
through Monday, although a corridor of 1.25 to 1.5" PWATs out
ahead of the warm front may result in locally higher QPFs (1.5+")
with some assistance from weak isentropic lift. Forecast for the
rest of Monday into Tuesday remains volatile as a trailing
shortwave brings additional chances for rain/storms to the
forecast area. No surface features or forcing mechanisms are
expected to accompany this shortwave, hence precip is expected to
be much lighter Monday evening into Tuesday. This being said, a
rumble of thunder wouldn`t be out of the question across central
Wisconsin Monday afternoon. Any storms that do pop up are not
currently expected to be severe.

Rest of the extended... The rest of the extended looks relatively
quiet as a higher amplitude blocking pattern sets up across the
central CONUS. A combination of robust upper-level ridging and
building surface high pressure will place most of the Midwest
under a south/southwest flow regime, acting to drag warmer air up
from the south. Consequently, temperatures will be on a steady
incline through the end of the week before potentially hitting 80
degrees on Saturday. It is worth mentioning that calm winds and
minimal cloud cover may drop temperatures down into the mid 30s
in the far north early Thursday morning, possibly enough to
warrant areas of patchy frost.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 630 PM CDT Sat May 25 2024

VFR flight conditions will continue through Sunday morning, with
mainly mid/high clouds. A few showers may brush through far north
central WI this evening, but should stay north of RHI.

A low pressure system and associated strong short-wave trough
will move into the region on Sunday. Showers will overspread the
region from SW to NE in the late morning and early afternoon,
and become heavy at times in the afternoon and evening. As the
showers increase, flight conditions will drop to MVFR/IFR. There
is question about how much instability will work into the region,
so have opted to leave any mention of thunderstorms out of the
TAFs for now.

Light S-SE winds will occur tonight into early Sunday, then
increase a bit from the SE-E during the day. Pockets of LLWS
will be possible in C/EC WI on Sunday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....RDM/Goodin
AVIATION.......Kieckbusch