433
FXUS63 KGRB 282040
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
340 PM CDT Sun Apr 28 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Periods of showers and moderate to heavy rain are expected
  tonight into Monday morning, which could result in isolated
  flash flooding in urban and low lying areas. Rivers will be on
  the rise through midweek, with a few of them reaching bankfull
  stage.

- Conditions hazardous to small craft are expected into Monday on
  the Bay and Lake. Patchy dense fog is possible on the waters as
  well.

- 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 the weekend.

&&

.DISCUSSION...
Issued at 339 PM CDT Sun Apr 28 2024

Short Term...Tonight and Monday

An area of showers, coincident with a mid-level shortwave, is
currently making its way through northern Wisconsin this
afternoon. Periods of showers will continue overnight as a surface
low slowly lifts from Iowa to Minnesota with the warm front
lifting from northern Illinois into southern Wisconsin, providing
isentropic lift across Wisconsin. There will be some modest
instability north of the warm front tonight; however, this has not
resulted in much in the way of thunderstorms across the area this
afternoon. Therefore, will remove thunder mention from the
forecast this evening and not include it until later tonight when
a swath of better MUCAPE advects north along with the approaching
warm front. Even this push of instability should only yield some
elevated thunderstorms overnight; mainly across central and east-
central Wisconsin. Some fog will be possible tonight as surface
winds decrease with fairly high dew points across the area. In
addition, some marine fog could advect in across east-central and
northeast Wisconsin near the lake and bay given the fairly cold
waters and warm air aloft. Temperatures tonight will remain fairly
close to what they are now and budge a few degrees higher or lower
depending on the location.

The aforementioned warm front will lift north on Monday morning,
allowing much of northeast Wisconsin to make it into the warm
sector. This will allow daytime highs to soar into the 60s across
much of central, east-central, and northeast Wisconsin with mainly
upper 50s across north-central Wisconsin. The warm front lifting
north is expected to provide a break in the precipitation Monday
morning, especially across central and east-central Wisconsin.
However, additional showers and thunderstorms are possible later
on Monday as some modest MUCAPE of 500 to 1000 J/kg builds across
east-central and northeast Wisconsin during the afternoon and the
cold front associated with the low sweeps through Wisconsin.

Long Term...Monday Night Through Sunday

Precipitation...A few showers, associated with the departing surface
low, will linger over far northeast WI Monday evening, before coming
to an end late Monday evening. This system will be followed by
surface ridging on Tuesday, leaving conditions dry across the area.
A quick-moving shortwave and surface cold front is still on track to
move across the state Tuesday evening through Wednesday morning. Due
to how quick this system is moving, the likelihood of a washout is
rather low. In fact, probabilities for QPF of 0.50 inch or more by
Wednesday morning are between 10-20% for central and north-central
WI, and less than 10% elsewhere. Cannot rule out a few embedded
thunderstorms as some models are indicating instability of a couple
hundred J/kg, but not anticipating any severe weather at this time.

Continuing to monitor guidance and trends for Wednesday night
through weekend, as there are still indications for a southern
stream system to potentially bring heavy rainfall to the area. There
are still timing and placement differences, but a general consensus
has the heaviest rain occurring Thursday night through Friday.
Thunderstorms will also be possible at times with this system, but
it is too difficult and early to determine when they will occur and
if they will become severe.

Temperatures...Southerly flow will lift warmer air into the region
for Tuesday allowing temperatures to rise above normal with highs
ranging from the mid 60s to low 70s. Despite the cold front moving
through Tuesday night, temperatures will rebound on Wednesday and
remain above normal with highs ranging from the mid 60s to mid 70s.
With potential for rainfall for the remainder of the extended,
temperatures will return to near normal.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1219 PM CDT Sun Apr 28 2024

A low pressure system tracking from the central Plains towards
the western Great Lakes will bring periods of showers and isolated
thunderstorms through Monday, most widespread this afternoon
through tonight. Hi-res models indicate instability is less than
previous runs; therefore, will remove thunder from the main TAF
sites as the chances for thunder have decreased.

CIGs will generally be MVFR this afternoon, with IFR conditions
spreading over most of the region later this afternoon and through
tonight. Conditions are expected to improve back to MVFR later on
Monday as the main low tracks through the area and some drier air
advects into the region.

Gusty northeast surface winds are expected this afternoon, with
surface winds easing overnight and becoming easterly. Some LLWS is
possible across central and north-central Wisconsin this evening
as low level winds from the southwest gust to 40 knots.

&&

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

&&

$$

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