NWS-Green Bay Forecast Discussion
FXUS63 KGRB 160800
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
300 AM CDT Sat May 16 2026
Forecast discussion for routine morning forecast 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 06Z TAF Issuance
Issued at 1054 PM CDT Fri May 15 2026
Main concern is thunderstorm potential over the new few hours.
Threat across central WI (KAUW and KCWA) looks to mainly be over,
with any lightning tracking to the north or south. Did continue
showers through 07-08Z. Ongoing thunderstorms in northern Oneida
County could reach KRHI at times over the next 2 to 3 hours, then
anticipate the thunder potential will shift east. Activity has not
reached east-central WI yet, but models still show some
development there after midnight. Maintained PROB30 groups for a
couple hours early tonight, with waning potential thereafter. All
rain and storms should be east of the area by 10Z. Severe
thunderstorm potential at this point looks very low.
LLWS develops this evening and then tapers off late tonight.
Southwest winds veer to the west Saturday morning, and then
increase with gusts to 25 kts again from late morning through the
afternoon.
&&
.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.......KLJ
FIRE WEATHER...Kieckbusch