614
FXUS63 KGRB 201712
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1212 PM CDT Wed May 20 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Frost or freeze headlines may be needed tonight as lows fall
  into the low to mid 30s over the Northwoods.

- Below normal temperatures continue throughout the week, warming
  back up during the Memorial Day weekend.

- Dry through at least early Friday with periodic rain chances
  throughout the Memorial Day weekend.

&&

.DISCUSSION...
Issued at 228 AM CDT Wed May 20 2026

Early Morning Analysis...Despite surface high pressure nudging into
the area from the west early this morning, isolated light rain
showers or sprinkles were occurring over north-central WI aided by a
500mb vort max overhead, with mostly cloudy skies occurring
elsewhere. The cloud cover will limit any frost development from
occurring this morning especially in far north-central WI where
temperatures are most favorable.

Rain Chances...The surface high pressure is progged to reside over
the area today into Friday, keeping dry weather in place for the
remainder of the work week. Model guidance is suggesting the next
chance for rain arrives Friday night into Saturday, as a southern
stream system lifts across IL/IN/MI. This would leave the forecast
area in the north/northwest precip shield of this system, minimizing
the potential for any thunderstorms. However, the latest guidance is
indicating the southern stream system may track further to the south
and east, lowering the potential for precip in the area for Friday
night into Saturday. Trailing behind this system is an upper-level
trough/frontal passage that looks to bring another chance for rain
sometime between Saturday night into Sunday, which may include the
potential for thunderstorms. There are also signs of a shortwave
moving over the area for Memorial Day, which could also bring rain
and thunderstorm potential. Despite these features, the Memorial Day
holiday weekend does not appear to be a washout, and more along the
lines of periodic chances for showers and storms.

Temperatures/Frost Potential...Below normal temperatures are
expected through Saturday, with today and Thursday being the cooler
of the days with highs in the mid 50s to mid 60s. Given the cooler
temperatures tonight (lows in the low to mid 30s across the
Northwoods and upper 30s to low 40s elsewhere) and high pressure
overhead, where clouds clear and winds become calm, anticipate frost
development, mainly across the Northwoods. A Frost Advisory will
likely be needed. High temps gradually warm into the 60s for Friday
and Saturday before rising into the 70s for Sunday, and potentially
into the 80s for early next week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1212 PM CDT Wed May 20 2026

Diurnal cumulus clouds will continue this afternoon with bases of
4-5k ft. These clouds should eventually dissipate this evening
with the loss of daytime heating and drier air works its way in
from the north. High clouds will stream in on Thursday with bases
above 10k ft.

Light northerly winds are expected before a lake breeze pushes
onshore from Lake Michigan, causing winds to switch to the east
late this afternoon and evening, reaching the central Wisconsin
TAF sites around 04z Thu. Light east to southeast winds are then
expected on Thursday.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion