SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1228 PM CDT Fri Jun 30 2023
Valid 011200Z - 021200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
EASTERN MISSOURI...CENTRAL AND SOUTHERN ILLINOIS...WESTERN INDIANA
AND WESTERN KENTUCKY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE
MID-MISSISSIPPI VALLEY TOWARD THE CENTRAL APPALACHIANS...AND PARTS
OF FAR SOUTHEAST NEW MEXICO INTO SOUTHWEST TEXAS...
...SUMMARY...
Severe thunderstorms will be possible tomorrow/Saturday, from the
central and southern Appalachians region westward through the
Ohio/Tennessee Valleys into the mid-Mississippi Valley. Severe winds
are the greatest concern, especially from eastern Missouri into
western Indiana.
...Synopsis...
A mid-level trough will traverse the central MS Valley region as a
second upper trough grazes the northwestern CONUS tomorrow
(Saturday). Ahead of the MS Valley mid-level trough, abundant
low-level moisture will be in place from the MS River to the
Atlantic Coast, fostering scattered to widespread thunderstorm
potential. Storms from today (Day 1) should be ongoing at the start
of Day 2 (Saturday) from the Plains into the OH Valley. Deep-layer
ascent associated with the progressing mid-level trough over the
Midwest, as well as low-level convergence along a trailing cold
front across the Southern Plains, will foster an increase in
convective coverage and intensity through the day, with severe
storms possible, especially across the Mid-MS Valley.
...Mid-MS Valley to the central Appalachians...
A complex severe weather scenario is expected to unfold across the
Midwest into the OH/TN Valley areas tomorrow, with later day
activity predicated on earlier day storms. At least scattered
thunderstorms (perhaps in the form of organized multicells/MCSs)
should be ongoing at the start of the period from the Midwest and
points east. Despite the variability in potential placement and
timing of earlier convection and subsequent impact on boundary-layer
modification, the latest guidance has come to a consensus that an
organized round of severe storms should occur from the mid-MS valley
and points east during the afternoon hours.
Along the periphery of the upper ridge, the embedded mid-level
trough should support convective initiation to the west of the MS
river by afternoon, where 70+ F surface dewpoints are overspread by
8 C/km mid-level lapse rates, resulting in 2000-3000 J/kg MUCAPE.
Strong speed shear with height will support elongated hodographs and
in turn, thunderstorm organization. Much of the latest
convection-allowing guidance portrays MCS development, with the
potential for severe winds, occasional bouts of large hail, and
perhaps a tornado or two. The MCS should form in MO by early
afternoon and progress eastward toward the Appalachians by early
evening, where Category 2/Slight Risk probabilities are in place. A
Category 3/Enhanced Risk also exists from the eastern MO into
western IN/KY, where confidence is highest in a relatively greater
concentration of severe gusts occurring during the mature stage of
the forecast MCS.
...Portions of the Hudson Valley...
Ahead of a surface lee trough, diurnal heating of a moist low-level
airmass will promote enough boundary layer destabilization to
support convective initiation across the Hudson Valley into the
central Appalachians during the late morning/early afternoon hours.
Given relatively poor mid-level lapse rates, tall and thin CAPE
profiles will promote enough buoyancy for strong but brief pulse
cellular convection and perhaps multicells when factoring in
mediocre vertical shear profiles. The strongest storms may produce
isolated severe wind/hail during the afternoon/evening hours,
warranting the maintenance of Category 1/Marginal Risk probabilities
this outlook.
...Southern Plains into the southern High Plains...
Thunderstorms may be ongoing at the start of the period across the
Southern Plains near the southward-sagging cold front. Through the
day, surface heating will destabilize the boundary layer as 7-8 C/km
mid-level lapse rates overspread mid to upper 60s F surface
dewpoints. 1000-2000 J/kg SBCAPE should manifest across the southern
Plains, with over 3000 J/kg SBCAPE possible closer to the Trans
Pecos in southwest TX. Vertical shear magnitudes should be modest at
best (generally under 30 kts of effective bulk shear). However,
elongated hodographs suggest that relatively robust multicellular
convection may initiate by afternoon, both along the cold front in
central OK into western TX, and along a dryline in western TX.
Severe wind/hail may accompany the more intense multicell clusters
that form, with the best chance for severe occurring across far
southeast NM into southwest TX, where a Category 2/Slight Risk has
been introduced.
..Squitieri.. 06/30/2023
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