ZCZC SPCSWODY2 ALL
ACUS02 KWNS 230600
SPC AC 230600

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
0100 AM CDT Thu Mar 23 2023

Valid 241200Z - 251200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS NORTHEAST
LOUISIANA...SOUTHEAST ARKANSAS...AND WESTERN MISSISSIPPI...

...SUMMARY...
Supercell thunderstorms capable of all severe hazards, including
strong tornadoes, are possible across the Lower Mississippi Valley
on Friday.

...Synopsis...
Upper troughing is expected to be in place over the western CONUS
early Friday morning. Strong mid-level flow will extend throughout
the periphery of this trough into the more confluent flow north of
the subtropical ridging across the eastern CONUS. A shortwave trough
is forecast to move through this enhanced mid-level flow, tracking
quickly eastward across the southern Plains during the day, and more
northeastward into the Mid MS Valley overnight. Mid-level flow is
expected to strengthen as the shortwave moves eastward, with 100+ kt
at 500 mb spreading across TX into the Mid-South.

At the surface, a low initially over north TX is forecast to move
northeastward ahead of the approaching shortwave, moving into
northern AR by Friday evening and through the Lower OH Valley
overnight. This low is expected to deepen throughout the day, and
this cyclogenesis will result in a broad area of moderate southerly
flow across the Lower MS Valley/Mid-South into the Southeast and TN
Valley. Environmental conditions appear favorable for numerous
severe thunderstorms from the Lower MS Valley through the Mid-South
and into the Mid MS and Lower OH Valleys.

...Lower MS Valley into the Southeast...
A broad warm sector, characterized by dewpoints in the upper 60s, is
forecast to be in place from east TX across much of the Lower MS
Valley and Mid-South early Friday morning. Thunderstorms may be
ongoing early Friday morning along a cold front moving eastward
across east TX. This cold front is expected to make gradual eastward
progress, as its parent surface low deepens while moving from
eastern OK into AR. This overall evolution will contribute to a
continued mass response across the warm sector, with low-level
moisture increasing throughout the day amid strengthen southerly
flow. This increase in low-level moisture coupled with modest
heating is expected to result in airmass destabilization during the
late afternoon. This destabilization coupled with large-scale ascent
attendant to the approaching shortwave (perhaps augmented by
low-level confluence) will likely result in discrete thunderstorm
development within the warm sector ahead of the front. 

Current thinking is that this initial development is most likely to
occur in the TX/LA border vicinity. The downstream air mass will be
moderately buoyant, with guidance suggesting MLCAPE around 1000-1500
J/kg and max 2-6 km AGL lapse rates around 8 deg C per km. Robust
vertical shear is also expected, with a strong low-level jet (i.e.
50-60 kt at 850 mb) developing during the evening beneath
strengthening mid-level flow. Forecast hodographs depict 
substantial low-level speeds and veering, with 0-1 km storm-relative
helicity from 200 to 300 m2/s2. A discrete supercell mode is
anticipated initially, with all severe hazards possible, including
strong tornadoes. With storms expected to develop in the LA/TX
border vicinity, discrete storm maturation is anticipated across
northeast LA, southeast AR, and western MS.

Upscale growth into a convective line is anticipated after this
initially discrete mode, with the line pushing eastward across MS
and AL overnight. Robust kinematic fields are expected to persist,
support a continued threat for strong gusts and line-embedded
tornadoes.

...Mid-South into the TN and Lower OH Valleys...
A more convoluted convective evolution is anticipated from
central/northern AR northeastward into the Lower OH Valley on
Friday. Storms will likely be ongoing along and north of stationary
boundary extending from east-central OK northeastward into northern
KY. A low-probability threat for hail is expected throughout the
morning and into the early afternoon as warm-air advection promotes
continued thunderstorm development along this boundary. 

A gradual increase in storm intensity is then expected during the
afternoon as the surface low begins to deepen across AR and
large-scale forcing for ascent attendant to the shortwave increases.
Buoyancy will be more modest than areas farther south, but the
strong ascent and increasing shear is still expected to support
intense updrafts. Given the presence of the stationary front and
stronger forcing, a linear mode is anticipated, with this line then
progressing quickly east-northeastward across the Mid-South during
the evening and into more of the Lower OH and TN Valleys overnight.
Strong wind gusts will be primary hazard within this line, but
line-embedded tornadoes will be possible as well.

..Mosier.. 03/23/2023

$$