LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0743 AM CDT Fri Jun 30 2023
Valid 301300Z - 011200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO EARLY TONIGHT ACROSS THE CENTRAL/SOUTHERN HIGH PLAINS EASTWARD
TO THE MID MS AND TN VALLEYS...
...SUMMARY...
Occasional large hail and damaging gusts will be possible this
afternoon into this evening across the central/southern High Plains,
and from the mid Mississippi Valley into the Tennessee Valley.
...Central/southern High Plains this afternoon/evening...
A midlevel shortwave trough will move eastward from the central
Rockies to the High Plains this afternoon and continue into KS
overnight. Lingering boundary-layer dewpoints in the low-mid 50s in
the post-frontal environment, steep midlevel lapse rates and surface
heating in cloud breaks (strongest in southeast CO) will result in
moderate buoyancy (MLCAPE near 1500 J/kg) and weakening convective
inhibition after 18z. The early arrival of the midlevel trough will
support relatively early storm development near and just east of the
Front Range, and storms will subsequently spread eastward over the
plains. The moderate buoyancy and effective bulk shear near 40 kt
(with relatively straight hodographs) will initially support a few
supercells capable of producing large hail near 2 inches in
diameter. Upscale growth into clusters/line segments appears likely
through the afternoon, and the potential for occasional severe
outflow gusts and isolated large hail will persist into early
tonight as storms spread eastward into KS.
Farther south, a weak surface trough/dryline will focus scattered
thunderstorm development this afternoon across the southern High
Plains. Deep-layer vertical shear will weaken gradually with
southward extent into west central TX, which supports a mix of
multicell clusters and transient supercells capable of producing
isolated strong-severe outflow gusts and large hail this afternoon
into this evening.
...Mid MS to TN Valley area through tonight...
The composite outflow from yesterday's MCS is still fairly well
defined from near I-70 in MO southeastward into western KY/TN, with
a substantially cooler/drier air mass farther northeast in IL/IN
this morning. Upstream storm clusters across southern IA/northern
MO will pose some threat for wind damage and marginally severe hail
this morning to near the MO/IA/IL border region, but the storms will
likely weaken thereafter while encountering the diminished buoyancy
toward IL. Other elevated storms are ongoing in a warm advection
zone across eastern TN/KY, and some of this convection could persist
while moving southward as the boundary layer destabilizes from
west-to-east through the day.
By afternoon, it appears that the primary focus for thunderstorm
development will be the composite outflow boundary, from east of a
weak surface wave in northwest MO continuing southeastward near
Saint Louis and into western KY and TN. Vertical shear will be on
the lower margins for sustained supercells, though continuing steep
lapse rates and large buoyancy will favor storm clusters capable of
producing damaging gusts and large hail. There is uncertainty
regarding whether or not a cluster or two will grow upscale and
persist into tonight, and how far east any such cluster (especially
if it originates across northern MO) could move with an attendant
threat for damaging winds. With no clear expectation for an
additional overnight cluster farther east, have reduced the Slight
risk area some across IN/southwest OH/northeast KY.
..Thompson/Gleason.. 06/30/2023
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