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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0100 AM CDT Wed Apr 13 2022

Valid 131200Z - 141200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE LOWER TO MID MISSISSIPPI VALLEY...

...SUMMARY...
Numerous severe thunderstorms appear likely today across a large
part of the lower/mid Mississippi Valley northward into the Midwest,
and lower Ohio Valley. Several tornadoes with some strong,
widespread damaging winds, some of which could be significant, and
large to very large hail will likely occur.

...Lower to Mid Mississippi Valley...
An upper-level trough will move quickly northeastward across the
southern and central Plains today, as a 90 to 100 knot mid-level jet
ejects northeastward into the mid Mississippi Valley. To the
southeast of the mid-level jet, a moist and unstable airmass will be
in place across the lower to mid Mississippi Valley. A convective
line will likely move eastward across southern Missouri and
northwest Arkansas during the morning. Other storms will develop
during the morning ahead of the line from the Arklatex northeastward
into the mid Mississippi Valley. A severe threat is expected to
develop early in the day, and ramp up quickly during the mid to late
morning as destabilization occurs.

By midday, moderate to strong instability will be in place from
northern Louisiana north-northeastward across eastern Arkansas,
where model forecasts have MLCAPE in the 2000 to 3000 J/kg range.
The southeastern edge of the mid-level jet will create strong
deep-layer shear across the western edge of the moist and unstable
airmass. RAP forecast soundings across eastern Arkansas into far
southeast Missouri by 20Z show loaded gun soundings with a shallow
capping inversion, 0-6 km shear in the 50 to 60 knot range, and 0-3
km storm relative helicity of 400 to 500 m2/s2. This should be very
favorable for supercells and tornadoes. Discrete supercells ahead of
the approaching squall-line should have potential for long-track
strong tornadoes. As the low-level jet strengthens during the mid
afternoon across eastern Arkansas, northwest Mississippi and far
western Tennessee, there will be a chance for an EF3+ tornado,
associated with the most dominating storm that occurs. Supercells
will also be capable of large hail and damaging wind gusts.
Hailstones of 2 inches in diameter will be possible with the more
intense supercells. As the squall-line further west organizes and
intensifies, widespread damaging wind gusts will beco*e likely
during the early afternoon. Some wind gusts of over 65 knots may
occur with the more intense and faster moving parts of the line.

The severe threat should continue eastward across western Tennessee
and northern Mississippi during the late afternoon and early
evening, where widespread damaging wind gusts will be likely. The
wind-damage and large hail threat should gradually beco*e more
isolated during the mid to late evening, as the squall-line
encounters weaker instability to the east.

...Midwest/Lower Ohio Valley...
An upper-level low will move east-northeastward across the northern
Plains today as an associated upper-level trough moves through the
central Plains. This trough will take on a negative tilt during the
day as a 90 to 100 knot mid-level jet ejects northeastward into the
mid Mississippi Valley. To the east of the mid-level jet, a corridor
of moderate instability will develop across eastern Missouri and
western Illinois by early afternoon. Thunderstorms will quickly
develop about that time along a cold front further west. These
storms will likely obtain a wind damage and large hail threat as the
convection organizes into a squall line. Severe thunderstorms will
also likely develop ahead of the line during the afternoon, with all
storms merging into a severe MCS by early evening.

The greatest severe threat is expected with discrete cells that
develop along and near the instability axis this afternoon. These
storms will likely beco*e supercellular and be associated with a
tornado threat, large hail and wind damage. RAP forecast soundings
along the instability axis at 20Z across southern Illinois and far
western Kentucky have MLCAPE in the 1200 to 1800 J/kg range with 0-6
km shear around 40 knots. 0-6 km shear is forecast to strengthen
markedly during the mid afternoon as the upper-level system pivots
into the region. This will create conditions very favorable for
supercells and tornadoes. 0-3 km storm relative helicity in the 200
to 300 m2/s2 range should support a potential for strong tornadoes.
Supercells will also be capable of large hail and wind damage.
Further west, the squall line along the front should gradually
intensify as instability increases during the afternoon. Widespread
wind damage appears likely with the more intense parts of the squall
line. Large hail may occur with the stronger cells embedded in the
line. The wind-damage threat will continue into early to mid evening
as the line moves eastward across the lower Ohio Valley, with the
severe threat eventually beco*e more isolated further to the east.

...Northeast...
An upper-level ridge is forecast to move northeastward across the
lower Great Lakes region today. Beneath the ridge, an axis of weak
instability is forecast to develop by afternoon from central New
York into central and eastern Pennsylvania. Although large-scale
ascent will be minimal, isolated thunderstorm development may occur
in the higher terrain as surface temperatures beco*e maximized
during the mid to late afternoon. RAP forecast soundings during that
time suggest that moderate deep-layer shear will be in place. This
co*bined with steep low to mid-level lapse rates may be enough for a
marginal severe threat. Any cell that can beco*e established in the
weakly forced environment could produce strong wind gusts and hail
for a brief time near peak heating.

..Broyles/Lyons.. 04/13/2022