436
FXUS63 KGRB 161438
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
938 AM CDT Sat May 16 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Elevated to near-critical fire weather conditions expected
  across northern WI this afternoon.

- Strong to severe storms and locally heavy rainfall from Sunday
  afternoon through Monday night. There is low confidence on the
  timing and coverage of severe storms.

- A return to drier and cooler weather is expected for the mid to
  late part of the next work week.

&&

.DISCUSSION...
Issued at 300 AM CDT Sat May 16 2026

Scattered showers and isolated thunderstorms were moving through
northern WI early this morning. The northern periphery of a
weakening thunderstorm complex was also impacting east central WI,
including the Fox Valley and lakeshore areas. Steady light to
moderate rainfall, a few embedded storms and wake-low enhanced
wind gusts to 30 to 40 mph were occurring there. All of the shower
and thunderstorm activity is expected to shift east of the region
by daybreak.

A much drier air mass will return to the forecast area today, with
PWATs dropping to 0.35 to 0.50 inch across northern WI. Expecting
a dry, warm and breezy day today, with highs in the middle 70s to
lower 80s, west winds gusting to 25 to 30 mph and very low
relative humidity. A cooler night is anticipated tonight, with
lows ranging from the upper 30s in the far north to around 50
south. Cannot rule out potential for patchy frost in far northern
WI, as MOS guidance shows a few of the colder spots dropping into
the middle 30s.

A 850 mb warm front will lift north through the forecast area on
Sunday, and bring an increasingly moist and unstable air mass to
the region. Showers and scattered thunderstorms will increase from
south to north during the day, with potential for strong storms
across parts of central and east central WI late in the
afternoon. Potential for strong to severe thunderstorms shifts
north across the forecast area Sunday night, as increasing
elevated instability (mid-level lapse rates of 7.5-8.5 C/km and
H8 LI`s of -3 to -6 C) and deep layer shear of 35-40 knots
supports a threat of large hail. Abundant cloud cover and showers
will hold temperatures in the upper 50s to lower 70s on Sunday.

A couple surface waves are expected to lift northeast along a
slow moving cold front, with one moving through north central WI
on Monday, and another stronger system moving through Monday
night. Could see a round of strong to severe storms Monday
afternoon as SBCAPE increases to 1500-2500 j/kg, and perhaps
another round as the cold front moves through Monday night.
Models all depict different scenarios regarding the timing of
the surface waves and subsequent cold frontal passage on Monday
night or Tuesday, so even though overall confidence in severe
weather is moderate through the Sunday afternoon to Monday night
period, confidence in the details(timing and coverage) is low.
With PWATs remaining in the 1.2 to 1.7 inch range through the
period, locally heavy rainfall is expected. Probabilities of 1+
inch of rain vary from 30-40% southeast to 50-80% northwest. For
amounts of 2+ inches, probabilities are reduced to 10-20%
southeast and 30-50% over the far northwest. Temperatures should
remain above normal during this period.

Models suggest the frontal boundary will move through the region
by Tuesday, followed by a period of dry and cooler weather
for the mid to late part of the next work week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 935 AM CDT Sat May 16 2026

Wide open VFR conditions expected through tonight with a few mid
clouds at times. Late tonight, mid clouds thicken from the south
as elevated warm front moves in. A spotty shower could develop
late in the south, but generally the rain holds off until later
Sunday. As rain showers build in on Sunday, conditions will trend
toward lower VFR with pockets of MVFR. Better chance of thunderstorms
will not be until later Sunday afternoon and into Sunday night.

West-northwest winds gust to 25 kts late this morning through the
afternoon. Winds lighten briefly this evening, then as cold front
drops in from the north, winds shift to northeast-east and could
gust to 20 kts briefly overnight tonight as the front first arrives.
As the sfc warm front remains to the south, easterly winds persist
across the area on Sunday, gusting to 15-25 kts.

&&

.FIRE WEATHER...
Issued at 300 AM CDT Sat May 16 2026

Pine fuels have reached their peak volatility and fine fuels have
still not greened up over northern WI, so dry, windy and warm weather
will bring elevated to near-critical fire weather conditions to
northern WI this afternoon.

Rain fell across northern WI last night, with some locations
receiving 0.25-0.40 inch in northwest Oneida, southeast Vilas and
the northern portions of Forest and Florence counties. Although
sunshine, low relative humidity (15-25%) and west winds gusting
to 25 to 30 mph will result in drying this afternoon, suspect that
the areas that received higher rainfall amounts may not become
critically dry. Given concerns with the dryness of fuels, plan
to just issue a Special Weather Statement for elevated to near-
critical fire weather conditions this afternoon.

&&

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

&&

$$

DISCUSSION.....Kieckbusch
AVIATION.......JLA
FIRE WEATHER...Kieckbusch

NWS GRB Office Area Forecast Discussion