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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1232 AM CDT Mon Aug 05 2024

Valid 051200Z - 061200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
FLORIDA...SOUTHEAST GEORGIA AND COASTAL SOUTH CAROLINA...OVER
PORTIONS OF THE UPPER MIDWEST...AND FROM THE UPPER OHIO VALLEY INTO
THE NORTHEAST...

...SUMMARY...
Severe thunderstorms are possible today and tonight from the Upper
Ohio Valley into New England, across portions of the Upper Midwest,
and from northern Florida into southern Georgia and southeast South
Carolina.

...Synopsis...

Several shortwave impulses/convectively enhanced vorticity maxima
will migrate through a broad area of northwesterly upper level flow
from the northern Plains to the Great Lakes. Meanwhile, an shortwave
trough embedded within the Hudson Bay upper cyclone will pivot
east/southeast toward the Northeast. Meanwhile, an upper shortwave
trough is forecast to overspread the Pacific Northwest, resulting in
enhanced westerly flow across the northern Rockies. Meanwhile,
Hurricane Debbie is forecast by the National Hurricane Center to
make landfall along the Florida Big Bend and move northeast into
southeast GA. Otherwise, an expansive upper anticyclone will
overspread much of the Great Basin/Four Corners region into the
Lower MS Valley. 

...IN/OH/MI into the Northeast...

West/southwesterly mid/upper flow will increase through the day as
the upper shortwave trough moves east across Ontario and into
Quebec. While deep-layer flow will mostly be unidirectional,
increasing midlevel flow will support effective shear magnitudes
around 35 kt. Midlevel lapse rates will remain poor, but a moist
airmass with dewpoints in the mid/upper 60s F will foster MLCAPE
values around 1000-2000 J/kg. Furthermore, heating into the mid 80s
to low 90s F will steepen low-level lapse rates. Forecast soundings
indicate supercell wind profiles, with forecast hodographs beco*ing
elongated/straight above around 2.5 km. This environment should
support a mix of supercells and clusters capable of damaging gusts
and isolated large hail. 

Further west across southern Lower MI, northern IN/OH and western
PA, stronger instability is forecast. A couple of rounds of
thunderstorms will be possible as an initial shortwave moves across
the area during the morning. Convection is then expected to form
during the afternoon and evening as a surface cold front sags
southward across the Great Lakes. While greater instability is
forecast, the stronger vertical shear will remain displaced to the
northeast across New England. Furthermore, morning convection could
be detrimental to afternoon storms depending how prevalent
convection is and how much cloud cover lingers over the area.
Nevertheless, forecast soundings indicate modestly steep midlevel
lapse rates will be present along with modest vertical shear,
supporting some risk of strong to severe thunderstorms capable of
damaging gusts and perhaps severe hail. 

...MN/IA into WI/IL...

A surface low is forecast to deepen over the Mid-MO Valley during
the afternoon/evening. A warm front will extend east/southeast from
the low across northern IA/IL. Thunderstorms are expected to develop
in a warm advection regime in the vicinity of the surface warm
front. However, it remains uncertain if warm-sector convection will
develop, or if convection will mostly be elevated to the cool side
of the warm front. Regardless, forecast soundings indicate supercell
wind profiles amid a very moist (70s F dewpoints) and unstable
airmass. Elevated convection will pose a risk for large hail. If
warm midlevel temps/capping can be overco*e and storms develop with
the warm sector, all severe hazards will be possible, including a
couple of tornadoes. Initial cellular convection will likely develop
into a more linear, forward-propagating mode during the evening as
storms move into southern WI and northern IL. Given uncertainty
regarding warm sector development, have maintained probabilities
from the previous Day 2 outlook, but upgrades could beco*e necessary
if trends toward warm-sector supercell development increase.

...FL/GA/SC...

The National Hurricane Center forecast has Hurricane Debbie making
landfall along the FL Big Bend vicinity this morning, and beco*ing
centered over southeast GA by Tuesday morning. Within the eastern
semicircle of the tropical cyclone across northern FL/southeast GA
and coastal SC, low-level SRH will be maximized within an airmass
characterized by mid 70s F dewpoints. Tornado potential will
acco*pany any deeper updrafts across this area.

...Northern Rockies...

Isolated to scattered thunderstorms are expected to develop during
the afternoon/evening as a weak upper shortwave trough impinging on
the region brings increasing ascent and midlevel moisture to the
region. Steep midlevel lapse rates will support up to around 500
J/kg MLCAPE. Around 25-35 kt effective shear magnitudes will allow
for organization of deeper updrafts. Meanwhile, a deeply mixed
boundary layer with inverted-v sub-cloud thermodynamic profiles will
support strong outflow gusts with this activity.

..Leitman/Thornton.. 08/05/2024