927
FXUS63 KGRB 082345
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
645 PM CDT Wed Apr 8 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Potential for heavy rainfall and thunderstorms this weekend into
  early next week. 1 to 1.5" of QPF expected, with up to 2"
  possible in spots. Strong or severe thunderstorms then possible
  Monday into Tuesday.

- Gale Warning remains in effect on Lake Michigan through this
  evening.

- Minor flooding continues along a few rivers, though runoff from
  melting snow in the Upper Peninsula paired with heavy rain may
  result in more widespread and significant flooding this weekend
  into early next week.

&&

.DISCUSSION...
Issued at 958 AM CDT Wed Apr 8 2026

Radar shows any remnants of the wintry mix from this morning
departing the area to the east as of early this afternoon.
However, we will only be afforded a brief dry spell before better
saturation returns late this afternoon into this evening with the
passage of a potent mid-level shortwave and tandem cold front.
This should bring an additional 0.25 to 0.5" of QPF across the
forecast area through Thursday morning. Narrow corridor of
elevated instability (200 to 300 J/kg) right along the front
would suggest that a rumble or two of thunder wouldn`t be out of
the question this evening, though no organized storms are
expected.

Transient shortwave energy paired with mid-level FGEN will bring
another quick-hitting round of light rain to northeast Wisconsin
Thursday night into Friday morning. Most areas should see under a
tenth of QPF, with highest amounts approaching 0.2" over east-
central Wisconsin.

Weekend rain/storm chances... Prevailing southerly flow and a
wide open Gulf will promote a period of prolonged active weather
through next week. Of particular concern will be the Monday into
Tuesday period as a deepening surface low and attendant cold
front track through the upper Mississippi Valley. PWATs ranging
from 1 to 1.25" would support a decent period of moderate to heavy
rain during this time, with probabilistic guidance showing a 10
to 30% chance for receiving 1.5" of QPF through Tuesday morning.
Modest instability (~1,000 to 1,200 J/kg MUCAPE) and appreciable
deep layer shear (45 to 55 knots) may result in the development of
strong or even severe storms late Monday into Tuesday, though
there are still timing discrepancies within the ensembles
regarding cold FROPA. This would likely make a difference in
whether or not surface-based storms would be able to develop, and
is worth monitoring in the coming days. Regardless, CSU and NCAR
machine learning algorithms highlight much of the upper Midwest in
a 15 to 30% prob severe out to Day 6.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 643 PM CDT Wed Apr 8 2026

Conditions are VFR this evening, but it is far from tranquil with
strong, gusty surface winds (over 30 kts at times since late
afternoon) and LLWS (SW at 015 up to 50 kts), not to mention area
of rain shifting over the region through this evening just ahead
of a cold front. Overall, expect borderline MVFR vsby with the
rain, but otherwise it will remain VFR. The rain moves through
quickly and surface winds will become not as gusty through the
night as winds shift from S/SW to W. Eventually toward daybreak on
Thursday the LLWS will end.

Late tonight into Thursday morning, sct-bkn MVFR stratocu clouds
will move into central and north-central WI (RHI, AUW, CWA).
The greatest chances for prevailing MVFR cigs will be at RHI
toward the Upper Michigan border. Elsewhere, scattered VFR clouds
will prevail through the day. Winds will be from the W/NW and not
as gusty as today.

&&

.HYDROLOGY...
Issued at 958 AM CDT Wed Apr 8 2026

Minor flooding continues on the Wolf River, persisting for the
better part of the next week. Fast flows and bankfull conditions
were observed elsewhere, namely on the Oconto, Menominee, and
Wisconsin rivers. Moving forward, active pattern with ample
moisture supply will continue to result in hydro concerns for the
foreseeable future, especially with PWATs nearing absolute max
relative to climo with the passage of another system this
weekend. Probabilities for receiving 1.5" of QPF currently range
from 10 to 30% during this time, which would only exacerbate soil
saturation and promote runoff. Convectively-enhanced rainfall
would also support river/stream rises early next week. Area of
particular concern looks to be the Menominee River and its
tributaries, where a signal for minor and even moderate flooding
exists due to the additional influence of snowmelt from the Upper
Peninsula.

&&

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

&&

$$

DISCUSSION.....Goodin
AVIATION.......JLA
HYDROLOGY......Goodin

NWS GRB Office Area Forecast Discussion