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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0301 PM CDT Thu Jul 21 2022

Valid 212000Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF NEW
ENGLAND...THE MID-ATLANTIC...AND SOUTHEAST STATES...

...SUMMARY...
Scattered severe thunderstorms capable of producing mainly damaging
wind gusts appear possible over parts of the Northeast and
Southeast, today through this evening.

...Northeast...
The Marginal Risk has been expanded into parts of NJ, where isolated
thunderstorm development has been noted this afternoon. Also, the
Slight Risk has been trimmed across parts of NY in the wake of
earlier convection. Otherwise, no changes have been made.
Strong/severe storms are ongoing this afternoon across parts of the
Northeast. Scattered damaging wind gusts will continue to be the
primary threat, though with several ongoing supercells noted,
isolated hail and a brief tornado remain possible. 
 
...Southeast into the Carolinas/Virginia...
The Slight Risk has been trimmed across parts of northwest GA, in
the wake of a southward-moving thunderstorm cluster, but otherwise
no changed have been made to the outlook across the Southeast into
the Carolinas/Virginia. See the previous discussion below for more
information. 

...Southern WI/Northern IL/Northwest IN/Southwest lower MI...
Increasing cumulus is noted this afternoon across southern WI into
northern IL, within a moderately unstable environment, and
confidence has increased regarding the potential for isolated to
widely scattered thunderstorms later this afternoon. Rather dry air
above the boundary layer may tend to limit updraft intensity to some
extent, but moderate deep-layer shear may support a few organized
storms into the early evening. Locally damaging wind gusts appear to
be the primary threat, with steep low-level lapse rates in place,
though some hail cannot be entirely ruled out. 

...Central/northern Plains...
The Marginal Risk has been expanded slightly southward across NE/IA,
based on the latest short-term guidance. Otherwise, no changes have
been made, see the previous discussion below for more information.

..Dean.. 07/21/2022

.PREV DISCUSSION... /ISSUED 1128 AM CDT Thu Jul 21 2022/

...Northeast States...
An upper low is tracking across southern Quebec today, with strong
westerly flow aloft across all of NY and New England.  Hot/humid
surface conditions are prevalent across this region with dewpoints
in the upper 60s and 70s, and temperatures near 90F.  This will
yield afternoon MLCAPE values of over 2000 J/kg.  Scattered
thunderstorms have begun to develop ahead of an approaching cold
front, and multiple lines/clusters of storms are expected through
the afternoon.  Damaging wind gusts will be the main threat,
although the strongest cells may occasionally produce hail.  An
isolated tornado is also possible.  Storms will spread eastward
toward the coast by late afternoon/evening, where marine influences
should temper convective intensity.

...NC/VA...
A weak upper trough is noted in water vapor imagery over WV/western
VA.  This feature and its associated 30+ kt mid level speed max will
track eastward across VA/NC this afternoon.  Strong heating and
ample low-level moisture will lead to scattered thunderstorm
development, with a few severe storms expected. Damaging winds will
be the main threat, mainly 18-01z.  

...GA/AL/MS/LA/AR...
A very moist and potentially unstable air mass is present today from
northern LA/southern AR eastward across into MS/AL/GA.  Forecast
soundings across this region show relatively steep mid-level lapse
rates and some dry air aloft, along max-heating MLCAPE values of
3000-4000 J/kg.  Most 12z CAM solutions indicate considerable
coverage of afternoon and evening thunderstorms across the SLGT risk
area.  Winds aloft are weak, which should limit convective
organization/maintenance.  However, thermodynamic conditions are
quite favorable for pulse/multicell storms capable of damaging
downburst winds.  Thunderstorms will build/propagate southward
during the evening before weakening due to diurnal cooling after
dark.