348
FXUS63 KGRB 161115
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
615 AM CDT Wed Jul 16 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Scattered strong to severe storms are expected today. The main
  hazards are damaging winds and heavy rain. A Flood Watch is in
  effect this afternoon and evening for central and east- central
  Wisconsin.

- Very warm and humid today, especially across central and east-
  central Wisconsin. Cooler and less humid conditions are expected
  late this week.

- Small craft should exercise caution on the bay of Green Bay this
  afternoon. A Small Craft Advisory is in effect for the bay and
  nearshore areas of Lake Michigan tonight into Thursday morning.

- Dry on Thursday and Friday, followed by rain and thunder chances
  late Friday evening and Saturday.

&&

.DISCUSSION...
Issued at 323 AM CDT Wed Jul 16 2025

Short Term...Today...Tonight...and Thursday

Synoptic Setup: A frontal boundary will linger across central
Wisconsin today, which will be the focus for a thunderstorm
complex to track through the area this afternoon and this evening
as a Mesoscale Convective Vortex tracks through southern
Wisconsin. This complex, seen on Water Vapor satellite imagery
over northwest Iowa, should track through the area rather
quickly, on the order of 3 to 6 hours depending on the speed and
track of the MCV. Showers and thunderstorms will then wind down
from west to east later tonight as the low tracks east and the
cold front pushes to the south. Cooler temperatures and drier
conditions are then expected on Thursday as high pressure builds
in across the western Great Lakes.

Flash Flood Potential: Despite a fairly fast moving thunderstorm
complex expected to track through Wisconsin this afternoon and
this evening, the atmosphere will be very juicy. PWAT values
across central and east-central Wisconsin are expected to be 1.75
to 2.25 inches, or 150-175% of normal and near the climatological
maximum for this time of year. 6 hour ensemble probability-
matched mean indicates 2 to 3 inches is possible, with amounts as
high as 4 inches not off the table as this system rolls through.
Ensemble probabilities of exceeding 2 inches are a healthy 40-70%
in this region with a respectable 20-40% probability of exceeding
3 inches. Flash Flood Guidance across the southern half of the
forecast area is only around 1.5 inches for 1 hour and 2 to 2.5
inches for 6 hours. Given these fairly low numbers for FFG and
high numbers and probabilities from the model QPF, there is a
high enough threat for Flash Flooding to issue a Flood Watch for
central and east-central Wisconsin this afternoon and into this
evening. Any urban areas, such as the Fox Valley, will be
especially susceptible given the plethora of hydrophobic surfaces
in these areas.

Severe Weather Potential: Recent CAMs runs indicate the best
potential for severe weather today appears to be across southern
Wisconsin as the MCV has trended south from previous runs. That
being said, SBCAPEs do rise to 1000 to 1500 J/kg across southern
portions of the region along with 30-40 knots of bulk shear. This
could bring strong to severe storms across central and east-
central Wisconsin if it can track through the area early enough
before the cold front pushes south, with the main threat being
damaging winds. Any storms near or north of the MCV or cold front
would also pose a threat for tornadoes given the enhanced 0-1 and
0-3 km SRH indicated by hodographs in that region. CAMs models
indicate the southern 2 tiers of counties will be most at risk for
severe weather this afternoon if our area is affected.

Long Term...Thursday Night Through Tuesday

Surface high pressure will lead to dry weather Thursday night and
Friday, with any precip holding off until at least Friday
evening. A surface boundary/weak front will move across Wisconsin
form the northwest on Saturday. Some weak forcing ahead of the
front could generate some showers/isolated thunderstorms late
Friday evening (15-25%), followed by a higher chance (30-45%) of
rain and thunderstorms on Saturday, coinciding with the surface
front, followed by a mid- level shortwave into Saturday evening.
While it is still early, models generally show less than 1000 J/kg
of CAPE and modest shear and lapse rates. While cannot rule out
isolated strong storms, it appears the threat for widespread
severe storms is currently low. Pwats climb to 1.50-1.75 inches
south of Hwy 29 on Saturday. This is in the 90th percentile of
climatology, so can not rule out some localized heavy rain or
minor flooding, but widespread threat is low.

High pressure returns on Sunday resulting in another dry day.
Temperatures and humidity levels will gradually increase
throughout next week. In addition, weak disturbances and frontal
boundaries will create on and off chances for showers and
thunderstorms next week. It will not rain all day or in every
location, but confidence in the specifics is low. It is too early
to determine any severe potential for next week.

Temperatures will be below normal on Friday with lows in the mid
40s to mid 50s, and highs in the low to middle 70s. Readings will
trend near normal through early next week, and then rise a few
degree above normal.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 555 AM CDT Wed Jul 16 2025

MVFR/IFR conditions have settled in across north-central
Wisconsin, while VFR/MVFR conditions have persisted across central
and east-central Wisconsin. The MVFR conditions across central and
east-central are mainly due to some patchy ground fog, which
should dissipate in a few hours.

For the rest of today, lingering low clouds and rain showers,
with some embedded storms also possible, will continue across
parts of northern WI during the morning. Then an area of showers
and storms is expected to move east across of the area this
afternoon. The showers/storms will bring MVFR CIGs (possibly IFR
at times), along with a threat for gusty winds and heavy rain.
Latest CAMs have the strongest storms just missing the area, but
still can`t rule out some stronger storms. Most of the storms look
to exit over Lake MI by 01-02z, with lingering showers and low
ceilings into this evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 1 PM CDT this afternoon through this evening
for WIZ030-031-035>037-045.

Flood Watch from 3 PM CDT this afternoon through this evening
for WIZ038>040-048>050.
&&

$$

DISCUSSION.....Kurimski/KLJ
AVIATION.......Kurimski