078
FXUS63 KGRB 302052
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
352 PM CDT Sun Jun 30 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

 - The typical cold spots over north-central Wisconsin could see
   low temperatures as cold as the middle 30s tonight. Widespread
   frost is not expected, but protecting cold sensitive plants is
   encouraged.

 - Periods of heavy rain will be possible from late Monday night
   through Tuesday night. There is a 50 to 75 percent chance of
   rainfall greater than 1 inch over central to east-central
   Wisconsin.

 - The next chance of widespread rain will arrive late on July 4
   into July 5.

&&

.DISCUSSION...
Issued at 352 PM CDT Sun Jun 30 2024

Short Term...Tonight and Monday

Quite weather conditions this afternoon as the 19Z surface analysis
shows a high pressure centered over the Twin Cities metro.
Temperatures this afternoon are running about 8 to 10 degrees normal
for the end of June with most of the region ranging from the middle
60s to low 70s. As the high shifts over the region tonight it will
create favorable radiative cooling conditions with low temperatures
overnight forecast to drop into the 40s at most locations. The
typical cold spots across northern WI may even see temperatures drip
into the middle to upper 30s. With isolated pockets of frost
possible sensitive plants should be covered or brought indoors.
Additionally, with the rapid overnight cooling patchy areas of fog
may develop early Monday morning, but should produce minimal
impacts.

With return flow setting up on the back side of the departing high
Monday morning cloud clover will start to increase from southwest to
northeast throughout the day, but the chance for showers and
thunderstorms should hold off until later Monday evening. With the
help of increasing southerly winds temperatures and dew points will
be on the rise Monday with afternoon highs forecast to reach the low
to middle 70s.

Long Term...Monday Night Through Sunday

Main focus throughout this forecast period revolves around the
potential for heavy rainfall late Monday through early Wednesday,
and the potential for showers and thunderstorms on the Fourth of
July.

Monday night through Wednesday morning...High pressure will give way
to strong moisture advection via an increasing southerly LLJ (35-50
kts) late Monday night. As a result, rain will spread/lift over the
area from the west. While thunderstorms are possible, instability
will be limited during this time, leading to a very low possibility
of severe weather. The bigger concern will be the heavy rainfall and
potential for flooding given PWATs of 1.75 to near 2 inches. By
Tuesday afternoon, probabilities for 1 inch or more are highlighting
central to east-central WI with 30-50%. A small lull in precip is
possible late Tuesday afternoon before the next chance for showers
and thunderstorms arrives with the passage of a cold front Tuesday
evening through early Wednesday morning. PWATs will still be in the
1.75 to 2 inch range during this time, raising concern for
additional heavy rainfall. Probabilities for an additional 1 inch or
more of rain are not as high as the first round of rain with values
between 15-35% across central and east-central WI. Additionally, due
to the timing of the frontal passage occurring Tuesday evening/night
and the better instability focused across southern WI, it will
become less favorable for surface based thunderstorms. But, elevated
thunderstorms will still be possible with the potential for a few
marginally severe storms. Overall, anticipate total rainfall amounts
of 1-2 inches across central and east-central WI, with lesser
amounts further north.

Independence Day through Friday...A low pressure system will track
across the Northern Plains into MN on Thursday, moving over WI on
Friday, and exiting over the central Great Lakes on Saturday.
Depending on the timing of this system, portions of central and
north-central WI may see impacts late in the evening on the 4th with
showers and thunderstorms. The remainder of the forecast area would
see the chances for showers and thunderstorms Friday through Friday
night. Will continue to monitor the timing of this system given the
busy holiday weekend.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1217 PM CDT Sun Jun 30 2024

VFR flying conditions are expected at all terminals through the
TAF period as a high pressure system settles in over the region.
A few isolated areas of fair weather cumulus clouds may develop
this afternoon, but should have minimal aviation impacts. Only
potential concern would be fog development overnight as winds
become calm, but was not confidence enough to include fog in the
TAFs at this time. Otherwise, winds will veer around and increase
Monday morning ahead of the next low pressure system. Flying
conditions will likely deteriorate Monday afternoon/evening as the
aforementioned low is forecast to bring periods of heavy rain to
the region through Tuesday.

&&

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

&&

$$

DISCUSSION.....GK/Kruk
AVIATION.......GK