NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 081813
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
113 PM CDT Wed Jul 8 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Scattered strong to severe thunderstorms remain expected this
  afternoon and evening, mainly between 3 and 8 PM over central
  and east-central Wisconsin. Damaging winds are the primary
  threat.

- Torrential rainfall rates of 2 to 3 inches per hour within the
  strongest storms will create a risk for localized flash
  flooding, especially in urban, low-lying, and poorly drained
  areas.

- Trends continue to be monitored for the excessive heat potential
  early next week.

&&

.DISCUSSION...
Issued at 112 PM CDT Wed Jul 8 2026

The latest RAP analysis and satellite/radar imagery show a cold
front stretching from west-central to north-central Wisconsin
early this afternoon. Morning showers and storms have exited over
northern Lake Michigan, giving way to partial clearing across
central and east-central Wisconsin where temperatures have warmed
into the lower 80s. Cooler temperatures in the lower to middle 70s
persist across the north where cloud cover and rainfall were more
widespread. Cloud cover is becoming more extensive again over
southern Minnesota in association with a remnant MCV. Focus of
this forecast remains on the severe weather and flash flooding
potential through this evening.

Severe Weather and Flood Outlook:  Destabilization is actively
taking place early this afternoon over central and east-central
Wisconsin where mixed- layer CAPE is climbing upwards of 1000
J/kg. With further solar heating, thunderstorms are expected to
redevelop in a buoyant airmass south of the front and across
central Wisconsin in the 18-20Z time frame. These storms should
track east through the afternoon before propagating southeast this
evening as a cold pool becomes established. Deep layer shear of
25 to 35 knots is expected in the area of greatest concern across
central and east- central Wisconsin. This shear profile will be
supportive of a few bowing structures and perhaps an isolated
supercell. Given the modest shear aloft, conditions will be most
favorable for damaging wind gusts rather than severe hail. High
freezing levels around 15,000 feet and poor mid-level lapse rates
do not favor large hail, except within the strongest rotating
updrafts. A weak, isolated tornado will also be possible, most
likely focused along an outflow boundary or lake breeze where low-
level vorticity is enhanced. The greatest period of concern is
from 3 to 7 PM before storms shift south and east of the forecast
area. Scattered shower and storm activity could persist into the
overnight period, but a stabilizing atmosphere should keep
intensities below severe levels.

Upper-level flow will be nearly parallel to the surface front
within a corridor of precipitable water values approaching 2.00
inches and high freezing levels. High rainfall rates of 2 to 3
inches per hour are expected in the strongest storms, which could
lead to localized flash flooding in vulnerable urban, low-lying,
and poorly drained areas.

Fog Potential Late Tonight:  After the rain winds down late
tonight into Thursday morning, there is a decent signal for fog
development, particularly across central to north-central
Wisconsin where clearing will occur first. Considerable
uncertainty exists regarding how long showers stick around into
Thursday. A moist boundary layer, weak cyclonic flow in the low
levels, and weak shortwave impulses aloft could keep light showers
lingering into the afternoon over central and east- central
Wisconsin.

Excessive Heat Outlook: An amplified upper air pattern featuring
a dominant upper- level ridge is expected to build northeast into
the region Friday through the weekend and persist into early next
week.

High pressure at the surface will slide across the area
Friday through the weekend. While minor signals for spotty shower
activity exist in some medium-range guidance, forcing is non-
existent beneath the building ridge, and a dry forecast has been
maintained.

The primary story in the extended period will be potential for
excessive heat. Very warm air aloft will accompany the building
ridge will argue for surface high temperatures climbing into the
upper 80s to lower 90s by Monday and Tuesday. Coupled with
humidities remaining high, minor heat- related impacts appear
possible at this time for those outdoors. Some relief from the
heat and humidity is expected towards the middle to end of the
next work week as the ridge begins to suppress southward.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1153 AM CDT Wed Jul 8 2026

Late this morning, a cold front stretches from west-central
Wisconsin to north-central Wisconsin. MVFR to IFR ceilings exist
along and north of the front while VFR conditions prevail to the
south and south of RHI.

This front will provide the focus for clusters of showers and
storms this afternoon and evening. Thunderstorm redevelopment is
expected 19-20Z with impacts into RHI/AUW/CWA starting during this
timeframe. These storms are expected to increase in coverage and
proceed into the Fox Valley in the 22-23Z period. Strong storms
are likely with gusts in excess of 40 mph possible with ceilings
and visibilities falling to MVFR and IFR/LIFR respectively.
After the initial push of storms, scattered showers with embedded
thunder looking to continue through much of the evening, while
light showers could persist across parts of central and east-
central WI into Thu morning.

Late tonight, there is a decent signal for ground fog to develop.
Central and north-central WI have potential for sub-IFR
visibilities. The fog should lift into a MVFR stratus deck after
about 15Z.

Winds will be light over the period.

&&

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

&&

$$

DISCUSSION.....MPC
AVIATION.......MPC