548
ACUS02 KWNS 071732
SWODY2
SPC AC 071730

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Tue May 07 2024

Valid 081200Z - 091200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
TEXAS INTO THE MID-SOUTH/MID MISSISSIPPI VALLEY AND LOWER OHIO
VALLEY...

...SUMMARY...
Scattered to numerous severe thunderstorms appear likely Wednesday
across parts of the southern Plains into the mid Mississippi, Ohio,
and Tennessee Valleys. All severe hazards, including tornadoes, very
large hail, and severe/damaging winds should occur. Some of the
tornadoes may be strong.

...Synopsis...

An upper low/trough, initially over the northern Plains Wednesday
morning, will develop east to the Upper Midwest/Great Lakes vicinity
by Thursday morning. Meanwhile, a more compact upper shortwave
trough over the Lower Great Lakes will shift east/northeast over the
Northeastern U.S. This regime will maintain a broad swath of 50-70
kt southwesterly midlevel/upper flow from the central/southern
Plains to the Midwest/Mid-South and Northeast. This broad area of
enhanced flow aloft will contribute to a strongly sheared
environment atop a very moist boundary-layer. While the upper
low/trough will progress east through the period, overall height
falls across the Midwest/OH-TN Valleys are expected to remain modest
until overnight. Large-scale ascent will be somewhat modest/nebulous
through the day, with mesoscale features/ascent perhaps more of a
driver of storm development/evolution.

At the surface, the general expectation is that a surface low over
MO early in the period will develop east across the Ohio Valley
vicinity. A warm front will extend east from the low across
IL/IN/OH, but there is quite a bit of variability in forecast
guidance regarding how far north this boundary will retreat during
the day. A cold front/dryline also is forecast to extend southwest
from the low across western MO/eastern OK/central TX during the
afternoon. The cold front will surge east/southeast overnight across
the Ozarks/Mid-South. These boundaries will collectively focus
thunderstorm development through the period.

...ArkLaTex into the Mid-MS/OH/TN Valleys...

A very moist and broad warm sector is anticipated, with surface
dewpoints in the upper 60s to mid 70s F already in place across much
of the region. Heating into the 80s F and a plume of steep midlevel
lapse rates overspreading the region will aid in strong
destabilization (MLCAPE 2500-4000 J/kg). With 40-50 kt effective
shear magnitudes, organized convection is expected. Convective mode
may be somewhat messy, with clusters/semi-discrete supercells and
bowing line segments possible. Little inhibition is expected across
the warm sector, so thunderstorm coverage could be quite widespread.

Initial thunderstorms development is likely during the morning near
the triple point in MO. Most guidance suggests this activity will
quickly grow upscale into an eastward advancing line/bow across MO.
More semi-discrete convection is then anticipated by midday/early
afternoon in the vicinity of the warm front across southern
IL/western KY, spreading eastward with time across IN/KY/southern OH
and TN. Additional storms are expected by mid to late afternoon
along the cold front across AR/southeast OK/northeast TX. Large to
very large hail (2-3 inch diameter) will be possible with more
cellular convection given very large instability, steep midlevel
lapse rates and favorable vertical shear. Tornado potential is also
apparent, given favorable low-level shear as is evident in enlarged,
curved 0-3 km forecast hodographs. Mesovortex tornado potential also
will accompany any bows/QLCS structures as well. Furthermore,
potentially widespread damaging/severe winds appears possible,
especially if strong enough cold pools can be generated within
linear segments.

Given little inhibition across the region and somewhat nebulous
large-scale forcing, convective evolution is somewhat uncertain
(widespread convection all at once vs. semi-discrete convection
growing upscale with time, etc). A corridor of higher probability
severe may develop from southeast MO/southern IL into western KY.
However, confidence is too low at this time for a categorical
upgrade.

...Iowa and Vicinity...

Isolated strong to severe thunderstorms appear possible in
associated with a cold-core upper low across parts of IA and
vicinity, mainly Wednesday afternoon. Although forecast instability
and deep-layer shear appear fairly weak/marginal, a few instances of
hail and strong/gusty winds appear possible. A brief tornado or two
may also occur along/near the occluded front.

...Southern New England into NY and the Mid-Atlantic/Carolinas...

Occasional hail and strong to locally damaging winds appear possible
with isolated thunderstorms across parts of NY into southern New
England as a surface low and attendant cold front move eastward
through the day.

Farther south into the Mid-Atlantic/Carolinas, more substantial
instability is forecast (up to 2500 J/kg MLCAPE). Large-scale ascent
is expected to remain weak over the region. However, strong heating
of a moist boundary-layer and the presence of a surface trough
extending southward into the Carolinas may be sufficient for greater
thunderstorm coverage than previously expected. As a result, a
Slight risk has been extended eastward across parts of VA/NC. Large
hail and damaging gusts will be possible with thunderstorm activity
through the evening.

..Leitman.. 05/07/2024

$$