689
FXUS63 KGRB 152347
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
647 PM CDT Mon Jul 15 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Isolated to scattered storms this evening. Some storms could be
  severe. Primary hazards are damaging winds and brief, but
  heavy, downpours.

- Mainly dry weather expected mid-late week into next weekend.
  Some small rain chances, but no widespread rain and severe
  weather is not expected.

- Not as warm and less humid on Tuesday. Temps drop below normal
  Wednesday, but are back around normal late this week into this
  weekend.

&&

.DISCUSSION...
Issued at 212 PM CDT Mon Jul 15 2024

Short Term...Tonight and Tuesday

Main forecast concerns will once again revolve around severe
weather potential for this afternoon and evening. Most likely
scenario shows isolated to scattered storms firing off along the
cold front during the mid to late afternoon, although there is
still some uncertainty with storm evolution later in the evening.

Convective trends/severe potential... Expect early to mid
afternoon to remain mostly dry as an MCS tracks from southern
Minnesota across southern Wisconsin. Attention then turns to storm
potential later this afternoon and evening as a robust cold front
sweeps across the forecast area. CAMs are still showing several
different scenarios for how convection will pan out. Cloud debris
combined with lingering precip from the aforementioned MCS may
act to hinder surface heating across central Wisconsin during the
day before additional cloud cover builds in ahead of the cold
front. This being said, low-level moisture (dewpoints in the low
70s) and resultant instability (3,000+ J/kg CAPE) would certainly
be enough to generate at least some discrete storms. As SRH (0-1
km SRH ~100 to 150) and deep layer shear (45 to 50 knots) increase
ahead of the front, it wouldn`t take a lot for any of these cells
to start rotating. Hence, a brief spin-up would not be completely
out of the question if convective elements are able to organize.
Primary threats will be gusty winds, hail, and locally heavy rain
as evidenced by inverted-V soundings, steep mid-level lapse
rates, and high PWATs. Suspect that widespread flooding concerns
will be kept at bay due to progressive storm motion. Main
flooding concern would result from training storms over the same
area. Limiting factors to storm development center around high
convective temperatures during the afternoon and coincident LCL
heights (above 1,000 feet) limiting storm coverage. Regardless,
current thinking is that isolated to scattered storms will ignite
along the cold front from north to south given frontal strength,
time of day, and pre- frontal unstable airmass.

Smoke trends... Models/satellite observations continue to show a
plume of near surface smoke skimming northern Wisconsin as a thin
layer of elevated smoke builds in from the west. Will continue to
monitor for air quality concerns and visibility reductions through
tomorrow as low-level smoke spreads across northern Lake
Michigan. Have thus opted to retain haze in the forecast through
tomorrow morning.

Tuesday... Models are picking up on scattered shower activity
tomorrow afternoon and evening as a shortwave dives down from
Ontario and into the Great Lakes region. Not expecting anything
strong to severe as large-scale subsidence behind the front will
place weak high pressure over the upper Midwest.

Long Term...Tuesday Night Through Monday

There will be some rain chances, but overall the pattern will turn
drier than it has been lately. Axis of mid-level trough that is
bringing the strong cold front across today will cross the upper
Great Lakes on Wednesday. A few showers possible Tuesday night and
more so on Wednesday as the trough approaches and then crosses.
High pressure builds in Thursday and Friday, leading to period of
dry weather. Temperatures will be seasonably cool on Wednesday
then trend toward normal late this week.

Looking ahead to the weekend and beyond, there will be some small
chances of mainly afternoon pop-up showers and maybe a storm, but
no widespread rain or severe weather is expected. Temperatures
will end up around normal with highs mainly in the lower 80s.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 647 PM CDT Mon Jul 15 2024

Scattered showers and thunderstorms are possible this evening as
a cold front moves across the region. Outside of any convection,
VFR conditions are expected. Some clearing is possible late
tonight and Tuesday morning, but high based cumulus clouds will
form in the afternoon, with isolated showers or thunderstorms
possible.

&&

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

&&

$$

DISCUSSION.....Goodin/JLA
AVIATION.......RDM