NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 141119
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
619 AM CDT Thu May 14 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Showers and isolated thunderstorms expected tonight into Friday.

- Gusty winds, warm temperatures, and low relative humidities will
  result in elevated to near-critical fire weather conditions at
  times from this afternoon through Saturday.

- Periods of heavy rainfall and strong to severe storms are
  possible Sunday night through Monday night.

&&

.DISCUSSION...
Issued at 232 AM CDT Thu May 14 2026

High pressure brought clear skies and light winds to the region
early this morning, with temperatures in the 30s to middle 40s.

High pressure will slide east today, but dry weather will persist
into the early evening, with only a gradual increase in high level
clouds expected. Temperatures will warm into the middle 60s to
lower 70s, except near Lake Michigan, where a lake/bay breeze
will keep readings in the middle 50s to lower 60s.

Strong return flow develops tonight, with a 35-50 knot low-level
jet ramping up WAA and advecting a moist air mass (PWATs 1.0-1.25
inch) into the region. Showers and isolated thunderstorms will
arrive in NC/C WI later this evening, but should have a tendency
to weaken as they shift into eastern WI overnight into Friday
morning. This trend will be due to a weakening low-level jet. The
showers will shift east of the region by late Friday morning, but
partial clearing and daytime heating should allow a few showers
and isolated storms to redevelop over the northwest half of the
forecast area during the late afternoon and evening. Lows tonight
will be in the 40s and lower 50s, with highs on Friday reaching
the middle 70s to lower 80s away from Lake Michigan. Cooler
readings in the upper 50s and lower 60s are expected along the
Lake Michigan shoreline due to onshore winds.

Models show a continued chance of showers and isolated storms
along a weak frontal boundary later Friday night into Saturday,
but would suspect that most of the area will be dry. A pattern
change to southwest flow aloft later in the weekend will bring an
increasingly moist and unstable air mass to the region. The
leading surge of moist and marginally unstable air will arrive on
Sunday, bringing a chance of showers and storms to mainly central
and east central WI in the afternoon. Low pressure developing in
the Central Plains on Sunday will lift northeast along a slow
moving cold front Sunday night through Monday night. This system
will generate periods of showers and storms, and locally heavy
rainfall, in an increasingly moist (PWATs of 1.2 to 1.7 inches)
and unstable air mass. Probabilistic forecasts show a 30-60%
chance of 1+ inch of rain from Sunday through Monday night, with a
10-30% chance of 2+ inches. Potential for severe thunderstorms
increases Sunday night, as increasing elevated instability and
steep mid-level lapse rates (7-8.5 C/km) support a threat of large
hail. Surface based instability increases to 1500-2500 j/kg
Monday afternoon and early evening, leading to potential for
surface-based severe storms as the cold front approaches the
forecast area. Temperatures should remain above normal during this
period.

Models have differing opinions on how quickly the cold front
will exit the region, with some as early as Monday night, and
others not until Tuesday night. Once the front clears the area,
drier weather and a return to near normal temperatures is
expected through the middle of next week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 610 AM CDT Thu May 14 2026

High clouds will gradually increase today into this evening, with
mid-level clouds and showers arriving in NC/C WI in the late
evening, then spreading east overnight. The showers will become
less numerous as they move into eastern WI, as a result of a
weakening low-level jet and a drier air mass. As the showers end,
lower ceilings will work their way into the western TAF sites,
though VFR flight conditions are expected to prevail through the
end of this TAF period.

Southeast to south winds will develop today, and become a bit
gusty later this afternoon into tonight. LLWS is expected to
develop over north central WI by late evening, and spread
southeast through the forecast area during the overnight period.

&&

.FIRE WEATHER...
Issued at 232 AM CDT Thu May 14 2026

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

Very low relative humidity (20-30%) is expected this afternoon,
but winds will only reach 8 to 15 mph.

A Fire Weather Watch has been posted for Vilas County Friday
afternoon and early evening. There is some uncertainty concerning
the dryness of fuels in NC WI, especially given expected rainfall
tonight. However, weather conditions should reach near-critical
levels, with highs near 80, RHs around 25% and southwest winds 15
mph gusting to 25-30 mph.

Dry air remains across northern WI on Saturday, with RHs dropping
to 18-25% along with west winds 10 to 15 mph with gusts to 20 to
25 mph.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Friday afternoon through Friday evening
for WIZ005.

Frost Advisory until 7 AM CDT this morning for WIZ030-031-
035>037-045.
&&

$$

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