NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 301730
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1230 PM CDT Mon Mar 30 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Mild temperatures this afternoon, with several locations across
  central Wisconsin reading in the upper 60s to low 70s.

- Potential for isolated strong storms tonight into Tuesday
  morning. Main threat with any stronger storms would be hail up
  to 1 inch. Storms may then re-develop Tuesday afternoon, though
  confidence in storm coverage and intensity is low.

- Winter weather impacts are likely Wednesday and Thursday, with
  both ice and snow accumulations possible.

- Hydro concerns arise later this week following the passage of
  two moisture rich systems.

&&

.DISCUSSION...
Issued at 1030 AM CDT Mon Mar 30 2026

Rain/storm chances... Main focus for the near-term continues to
revolve around strong or severe storm potential tonight. Expect
scattered showers and embedded storms to develop within WAA regime
ahead of the front later this afternoon as parent low passes to
our south. Overall, not many changes from going forecasts, as dry
air entrainment from high pressure over the northern Plains will
continue to be a hindrance to storm initiation. Additionally, find
it hard to believe that we will get any surface-based convection
given placement north of the boundary, elevated CAPE beginning
~700 to 600 mb, and robust surface capping due to northeast flow
off of Lake Michigan. If anything does manage to fire, greatest
threat looks to be hail given elongated hodographs and steep mid-
level lapse rates. Brief window for light icing (mainly on
elevated surfaces) still appears possible across the far north
late tonight into early Tuesday morning as colder air wraps in
around the back edge of the departing low, though impacts should
be minimal.

As the surface low continues to track into lower Michigan on
Tuesday, a conditional chance exists for storms to re-develop
during the early to mid-afternoon window, mainly over east-central
Wisconsin. Par for the course, storm initiation may be hampered by
lingering cloud debris from early morning convection and whether
or not we can get sufficient surface heating to warm to convective
temperatures. Overall appearance is that of a classic early spring
marginal risk, with low confidence in both storm coverage and
intensity.

Wintry system late week... Following a brief lull in precipitation
on Wednesday, fake spring comes to an end as another Colorado low
treks north into the Great Lakes. Still lots of questions with
this system, though a slew of different p-types seems inevitable.
Ensembles seem to be honing in on the track of the low, which
would bring the main deformation precip shield into Wisconsin by
late Wednesday afternoon. Still remains to be seen whether or not
we end up on the warm or cold side of this system, though concerns
arise as the most recent suite of long-range guidance shows a
prominent warm nose making it into central and east-central
Wisconsin. As such, icing probabilities have trended up
significantly from yesterday's forecast package, with probabilities
for receiving 0.25 inches of ice now standing at around 30 to 50%
across portions of central Wisconsin to the Fox Valley. This is
well-represented in the WSSI-P by a 50 to 70% chance for moderate
winter storm impacts, weighed heavily on ice accumulation.
Snowfall trends have also increased and shifted further north,
with 20 to 40% chances for receiving 6 inches of snow generally
north of Hwy 29. In addition, ample moisture transport from a wide
open Gulf would place east-central Wisconsin near the 99th
percentile for QPF relative to climo, with ECMWF EFI and shift of
tails forecast suggesting higher confidence in boom potential.
Overall, any wobble in surface temperatures and the strength of
the warm layer aloft will play large roles in what the dominant
p-type will be, which bears monitoring in the coming days.

Late week/hydro concerns... Active pattern remains full steam
ahead as 500 mb wave train continues to amplify toward the end of
the week. Another system, albeit slightly warmer, arrives this
weekend and is progged to dump another round of QPF over
northeast Wisconsin. Dominant p-type at this time looks to be
rain, though any changes in the track of the low would change
this. The cumulative effect of two moisture rich systems over the
course of the week will be the development of hydro concerns,
with a signal for river and stream rises already showing up. Minor
flooding would likewise be possible in low-lying and poor drainage
areas.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1030 AM CDT Mon Mar 30 2026

VFR flying conditions prevail for the remainder of the afternoon
and into this evening. Conditions then deteriorate to MVFR this
evening and overnight as scattered showers and embedded storms
arrive in the vicinity of a cold front. Coverage and intensity of
storms remains uncertain, though an isolated storm or two could
become strong this evening into Tuesday morning. Hail would be the
main threat in this case. Tried to provide timing resolution where
possible in the TAFS via inclusion of PROB30 groups for -TSRA,
though there remains a small chance that some terminals could
remain dry during the overnight period.

Expansion of stratocu occurs early Tuesday morning in proximity to
the front as cigs drop to IFR. Possibility for isolated storms to
re-develop during the afternoon, though have withheld thunder
mention in the TAFs due to low certainty. Otherwise, winds will be
predominantly out of the northeast, gusting between 15 and 20
knots.

&&

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

&&

$$

DISCUSSION.....Goodin
AVIATION.......Goodin