RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Fri Oct 22 11:58:02 UTC 2021.
No Mesoscale Discussions are in effect as of Fri Oct 22 11:58:02 UTC 2021.
SPC 0730Z Day 3 Outlook
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...
...SUMMARY...
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
Oregon.
...Eastern Kansas and Oklahoma into the middle Mississippi Valley
region...
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.
...Coastal Oregon...
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.
..Dial.. 10/22/2021
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0401 AM CDT Fri Oct 22 2021
Valid 251200Z - 301200Z
...DISCUSSION...
Monday (day 4) - Some severe threat will probably persist with the
low amplitude shortwave trough as it continues through the TN and OH
Valleys during the day and into the Middle Atlantic overnight.
However, the moist corridor west of the Appalachians is forecast to
be rather narrow. Timing of this system east of the Appalachians
will be towards evening into the overnight. There is lingering
uncertainty regarding the quality of the thermodynamic environment.
As a result will not introduce a categorical risk area for this
outlook, but will re-evaluate in later updates.
Tuesday (day 5) - A strong upper trough is forecast to undergo
significant amplification as it moves through the southern and
central Plains. Moisture return and instability in advance of this
system should become sufficient for severe storms along and ahead of
the attendant cold front, with greatest threat expected over a
portion of the central and southern Plains.
Wednesday (day 6) - A threat for severe storms might persist as the
upper trough continues through the Southeast States during the day
and into the evening where gulf moisture return will be greatest.
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