033
FXUS63 KGRB 151105
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
605 AM CDT Tue Jul 15 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Isolated showers and storms this morning in far northern WI.
  Followed by scattered storms across northern WI late this
  afternoon into tonight. Severe storms are possible far north-
  central WI during the late afternoon/evening with a marginal to
  slight risk for severe weather. Heavy rain also a risk.

- Staying active with showers and a chance of storms Wednesday
  through Wednesday evening. Marginal to slight risk of severe
  storms and heavy rainfall in central and east-central WI.
  Lingering scattered showers on Thursday, then dry for the end of
  the week.

- Very warm and humid through Wednesday. Heat index values peaking
  in the lower to middle 90s today. Cooler and less humid late
  this week.

&&

.DISCUSSION...
Issued at 348 AM CDT Tue Jul 15 2025

Short Term...Today...Tonight...and Wednesday

Dry conditions along with warm and moist air will prevail across
the area early this morning. There will be a couple of
opportunities for showers and thunderstorms today, with the first
possible later this morning across north-central Wisconsin as a
weak mid level shortwave tracks through the northern Great Lakes
region. This activity is already firing up across northwest
Wisconsin. This activity is not expected to be severe and should
shift northeast late in the morning into the early afternoon.

The outflow boundary from this system along with an upstream cold
front will be the impetus for additional activity later this
afternoon across northwest Wisconsin as it tracks east through
north-central Wisconsin late this afternoon and into the early
evening. This activity is generally expected to weaken as it
tracks through the area; however, if this activity can track
through the area early enough there will be enough instability and
shear for strong to severe storms. SBCAPEs are expected to be 1500
to 2000 J/kg along with 30 knots of bulk shear. This would be
enough to produce damaging winds and large hail if storms roll
through early enough before instability and shear wane or the
system weakens. Heavy rain will also accompany any thunderstorms
across north-central Wisconsin this afternoon as PWAT values hover
around 150 percent of normal.

Another hot and humid day will be on tap today as highs range
from around 90 across central and east-central Wisconsin with
middle to upper 80s across north-central Wisconsin. The warm
temperatures and high dew points will push heat index values into
the lower to middle 90s across much of the area this afternoon.

The cold front lingers across north-central Wisconsin tonight,
with precipitation chances uncertain. It appears the best chance
would be across north-central Wisconsin tonight, with some models
indicating precipitation along the front may wipe out with only
some light rain or possibly mostly dry conditions could occur.
Given the model uncertainties will keep rain chances limited to
the north.

Rain chances increase on Wednesday as a shortwave tracks through
the western Great Lakes, which will push the stalled out cold
front through the region. Although the best potential for severe
weather on Wednesday appears to be across southern Wisconsin,
SBCAPEs do soar to 1500 to 2000 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. CAMs models indicate the southern 2 tiers of
counties will be most at risk for severe weather Wednesday
afternoon. Heavy rain will again be possible as PWATs will be 125
to 150 percent of normal for this time of year.

Temperatures on Wednesday will vary greatly due to the cold front,
with highs ranging from around 60 across the far north, to the
lower to middle 80s across the southern 2 tiers of counties.

Long Term...Wednesday Night Through Monday

Lingering activity Wednesday evening as a surface front, mid-level
short wave, and upper jet continue to track across Wisconsin.
Instability still as high as 1500 J/kg at 00Z/Thu, and pwats as
high was 1.75 inches; however, both of these parameters quickly
wave as the sun sets and drier air filters in from the northwest
behind the front. A couple hours of isolated strong/severe storms
with strong winds and heavy rain are possible Wednesday evening,
following by a few lingering non-severe storms or rain showers
the rest of the night.

Surface high pressure will lead to dry weather for the rest of
Thursday and Friday. Temperatures will be cooler/less humid with
the arrival of cooler and drier air behind the front. Highs on
Thursday will be in the low 70s, and in the mid 70s on Friday.

Weak disturbances will create on and off chances for showers and
thunderstorms from Saturday into early next week. Right now, the
most likely days for any precip are Saturday afternoon and
evening, and late Monday into Tuesday, but confidence in the
specifics is low. It is too early to determine any severe
potential this far out, but as previously mentioned, the higher
instability is currently progged much farther south and west.
Temperatures from Saturday into early next week will be near
normal.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 559 AM CDT Tue Jul 15 2025

Some minor VSBY restrictions due to patchy fog will clear out
shortly after TAF issuance. Otherwise some high clouds are
streaming in across the region, with bases of 10-15k ft. SCT
cumulus clouds may redevelop due to the heating of the day today,
with bases around 4k ft. A line of thunderstorms is expected to
reach north-central Wisconsin late this afternoon into this
evening, with the best chance at RHI. The line should weaken as it
pushes southeast and should not make it much past KAUW/KCWA.
Therefore will maintain the TEMPO across KRHI and the PROB30
across KAUW/KCWA with dry conditions elsewhere. MVFR conditions
should overspread north-central Wisconsin as the showers and
thunderstorms move through, with IFR CIGs developing north of KRHI
later in the evening.

Light S-SW winds this morning will become gusty later this morning
through the afternoon, then subsiding this evening.

&&

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

&&

$$

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