SPC AC 220740
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0240 AM CDT Fri Oct 22 2021
Valid 241200Z - 251200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER THE MIDDLE
MISSISSIPPI VALLEY REGION...
Severe storms with all hazards possible are expected over a portion
of the middle Mississippi valley region Sunday afternoon and Sunday
night. A few strong to severe storms are also possible over coastal
...Eastern Kansas and Oklahoma into the middle Mississippi Valley
A low-amplitude shortwave trough will move through KS and OK during
the day, reaching the middle MS Valley later Sunday afternoon and
evening. The attendant surface low will move from northeast KS
during the morning into IL overnight. Trailing front will sweep
across KS and OK into the MS Valley, reaching the TN and OH Valleys
overnight. A warm front will extend east from the low and spread
northward through the OH Valley.
The pre-frontal warm sector is expected to become moderately
unstable supported by the northward advection of low to mid 60s F
dewpoints. Low clouds may accompany this moisture return, but some
breaks should allow for pockets of diurnal heating of the boundary
layer with MLCAPE from 1500-2000 J/kg MLCAPE. Low clouds and a
modest cap may delay storm development until mid afternoon when
storms should initiate along the cold front from eastern KS into
eastern OK. Wind profiles with up to 50 kt effective bulk shear and
sizeable low-level hodographs will support supercells. Storms may
eventually evolve into lines during the evening as they continue
through the MS and TN Valley regions. All severe hazards are
possible including potential for significant severe weather.
A substantial upper trough will amplify as it approaches the west
coast accompanied by cold air aloft and steep lapse rates. This will
contribute to marginal surface-based instability, especially along
coastal OR where vertical wind profiles with strong vertical shear
will support a conditional threat for organized storms including
low-topped supercells during the late afternoon into the evening.
This region will continue to be monitored for a possible SLGT risk
in later updates.
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z