761
FXUS63 KGRB 292350
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
650 PM CDT Mon Apr 29 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Due to recent rainfall, rivers and streams will be on the rise
  through midweek, with a few of them possibly reaching bankfull
  stage.

- There is a chance of showers and a few thunderstorms Tuesday
  night. Additional rain and thunderstorm chances are possible at
  times from late Wednesday night through Friday.

&&

.DISCUSSION...
Issued at 407 PM CDT Mon Apr 29 2024

Short Term...Tonight and Tuesday

As a surface low gradually tracked northeast from southeastern MN
into northwest WI this afternoon, a line of scattered showers
developed along its occluded front over eastern WI early this
afternoon. Embedded thunderstorm development had not been observed
despite a couple hundred of elevated instability analyzed this
afternoon. The lack in thunder could be a result of a lack of mid-
level moisture, too weak of instability, and low mid-level lapse
rates. Therefore, the chance of thunderstorms developing for the
remainder of the evening remains very low. As the surface low
continues to track into Upper MI into this evening, the line of
scattered showers will exit the forecast area to the east/northeast.

For the remainder of the night, the mid-level shortwave associated
with the surface low will shift overhead. Forecast soundings
indicate enough low-level moisture in central WI and across the
Northwoods to generate low clouds through Tuesday morning. A few
sprinkles may accompany the low clouds through late this evening
with potential for fog to redevelop later tonight through early
Tuesday morning.

Ridging will follow the shortwave for Tuesday, allowing clouds to
decrease for the return of some sunshine. The timing of the ridging
has slowed slightly from the previous forecast, causing the warmer
air to reach the area a little slower. Therefore, lowered Tuesday`s
highs by a few degrees. Still anticipate highs mainly in the 60s,
but have removed the 70s from the southern portion of the forecast
area.

Long Term...Tuesday Night Through Monday

A mid level PV anomaly and attendant trough will bring showers and
thunderstorms to northeast Wisconsin Tuesday night as this feature
tracks through the western Great Lakes region. This feature should
mainly be out of the region by Wednesday morning, with some
showers possibly lingering across far northern Wisconsin Wednesday
afternoon.

Wednesday is expected to be dry, warm, and breezy behind the
departing low. These conditions could cause some fire weather
concerns as relative humidity values plunge along with the gusty
winds and warm afternoon temperatures. The main factor that may
prevent elevated fire weather conditions will be the rain on
Tuesday night and the relatively short period these conditions are
expected given more precipitation is expected later in the week.

A well organized low pressure system emerging over the central
Plains will lift northeast towards the upper Mississippi Valley on
Thursday then the northwestern Great Lakes region Thursday night.
This system will bring a prolonged period of showers and
thunderstorms at times from late Wednesday night through Friday.
The prolonged period of precipitation will keep temperatures
cooler than earlier in the week; however, temperatures will still
be around or slightly warmer than normal for this time of year.
The prolonged precipitation will also bring flooding concerns as
area rivers have risen a bit from this weekends event, with an
additional period of rain causing area rivers to reach bankfull,
depending on how much rain falls and where later this week.

The models this weekend indicate there will be another period of
rain at some point, but at different intensities. The
GFS/Canadian have precipitation Saturday and Saturday night, with
a bit more QPF and a stronger low pressure system. The ECMWF
indicates a much weaker low with a paltry amount of QPF on
Saturday. AFter the weekend, the ECMWF brings another low pressure
system with a healthy amount of rain on Monday while the
GFS/Canadian are dry with a high pressure system across the Great
Lakes. Given the model differences will stick with the NBM in that
portion of the forecast as things are still up in the air.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 650 PM CDT Mon Apr 29 2024

Low pressure moving slowly across Upper Michigan will
keep cloudy skies across the area overnight. Ceilings will fall
to MVFR west of a ESC to DLL line, with IFR ceilings northwest of
an IMT to AUW line. VFR ceilings are expected across eastern
Wisconsin.

Ceilings will begin to rise Tuesday morning, with rapid clearing
from south to north during the afternoon. VFR conditions are
expected Tuesday evening, but showers and thunderstorms and lower
flight conditions are likely later at night as low pressure
approaches from the Plains states.

&&

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

&&

$$

DISCUSSION.....Kruk/Kurimski
AVIATION.......RDM