SPC Apr 20, 2024 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0735 AM CDT Sat Apr 20 2024

Valid 201300Z - 211200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
THROUGH LATE EVENING ACROSS CENTRAL/SOUTH TX...AND FROM SOUTHERN MS
TO SOUTHERN NC...

...SUMMARY...
Marginally severe storms capable of strong wind gusts and hail will
be possible mainly this afternoon/evening across portions of central
and south Texas, and from southern Mississippi to southern North
Carolina.

...TX into the Southeast this afternoon/evening...
South of a midlevel trough over the Great Lakes, a southern-stream
shortwave trough will progress eastward from southern AZ/NM toward
the lower MS Valley by Sunday morning. An associated surface
baroclinic zone from south TX into the Carolinas will move only
slowly southward through the period, providing a focus for isolated
to scattered thunderstorm development. The more widespread
convection is expected across TX near and to the north of the front,
based on proximity to the richest moisture and the southern-stream
trough.

Boundary-layer dewpoints in the 60s and surface heating in cloud
breaks will drive MLCAPE in the 1000-2000 J/kg range immediately
south of the front across the Southeast this afternoon. Vertical
shear will be relatively weak as a result of westerly wind profiles
with only modest speed increases from the low to midlevels. The
moderate buoyancy, weak vertical shear and steep low-level lapse
rates will favor isolated strong/damaging outflow gusts for a few
hours this afternoon/evening.

Richer low-level moisture (dewpoints in the lower 70s) and steeper
midlevel lapse rates will be present across south TX through this
evening. Initially elevated convection is expected to increase atop
the frontal surface from west central into central TX, and some of
this convection will approach the surface front this afternoon.
Separate surface-based thunderstorm development is also expected
along the front, and the storms will subsequently spread
east-southeastward into early tonight. Despite MLCAPE potentially
exceeding 2000 J/kg, the steeper lapse rates will be relatively high
in the profiles (above the 700 mb level), and vertical shear will
not be particularly strong. Though isolated large hail and wind
damage will be possible, along with some clustering of storms later
this afternoon into early tonight, a MRGL risk (5% hail/wind and 2%
tornado) appears to best characterize the overall severe threat in
TX.

..Thompson/Kerr.. 04/20/2024


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SPC Apr 20, 2024 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1243 AM CDT Sat Apr 20 2024

Valid 201200Z - 211200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF CENTRAL/SOUTH TEXAS AND ACROSS PARTS OF THE SOUTHEASTERN US...

...SUMMARY...
Marginally severe storms capable of strong wind gusts and hail will
be possible across portions of central and south Texas, and during
the afternoon from southern Mississippi/Alabama across parts of
Georgia and into southern South Carolina.

...Texas...

Southern stream remains active early this morning. One weak
mid-level disturbance is advancing east across the lower Rio Grande
Valley, while a second more significant short-wave trough is located
upstream over the lower CO River Valley/Baja region. This feature is
forecast to progress into west TX by 21/00z, then deamplify as it
approaches the upper TX Coast late in the period. Large-scale
pattern favors surface ridging across the middle of the country and
a dominant high pressure will remain wedged deep against the higher
terrain of the Rockies. With time the leading edge of this air mass
will surge into the lower Rio Grande Valley with the surface front
expected to move off the lower TX Coast by 21/12z.

Early in the period, low-level warm advection will focus along a
corridor arcing from the Edwards Plateau into the Red River region
of north TX/southern OK. Elevated convection will be common at the
start of the period. Considerable amount of elevated convection will
likely persist north of the front through the period, gradually
sagging south as the short wave approaches and the front advances
into lower latitudes. Forecast soundings do not exhibit very steep
low-level lapse rates along/near the front and this should limit
surface-based convection through the period. Most storms are
expected to develop north of the boundary. Even so, some risk for
hail/wind will be noted with thunderstorm clusters. If frontal
convection can develop there is an outside chance for a brief
tornado with surface-based supercells.

...Southeast...

Surface front is forecast to be draped across the Carolinas-central
GA-southern AL/MS early in the period. This boundary will move
little during the day and will serve as the main focus for
convective development as boundary layer temperatures warm and
low-level lapse rates steepen. Forecast soundings suggest convective
temperatures will be breached by early afternoon and scattered
thunderstorms are expected to develop. Early-morning water-vapor
imagery suggests the weak short-wave trough over deep south TX may
contribute to convection along/near this boundary later today. If
so, some clustering is possible given the large-scale assistance. At
this time locally damaging winds appear to be the primary risk.

..Darrow/Weinman.. 04/20/2024


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SPC Apr 20, 2024 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0748 PM CDT Fri Apr 19 2024

Valid 200100Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe threat appears minimal with thunderstorms tonight.

...01z Update...

Very isolated thunderstorms continue this evening across the
southern Appalachian region into the Carolinas. This activity
developed in large part due to strong boundary-layer heating in
conjunction with frontal forcing and orographic influences. However,
nocturnal cooling and weak large-scale forcing favor gradual
weakening over the next few hours. While a few flashes of lightning
will be noted with the most robust updrafts, the probability of
severe appears too low to warrant a MRGL risk overnight.

Upstream, weak mid-level short-wave trough is advancing across far
west TX. This feature will encourage weak LLJ across the Edwards
Plateau later this evening, and a corridor of focused low-level warm
advection will become established from northwest TX into the Red
River region late. Elevated thunderstorms will develop along this
zone, and while hail can't be ruled out with the strongest storms,
the risk of hail, in excess of 1 inch, appears too low to warrant
severe probabilities.

..Darrow.. 04/20/2024


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SPC Apr 19, 2024 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1126 AM CDT Fri Apr 19 2024

Valid 191630Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
SOUTHEAST...

...SUMMARY...
Sporadic strong to marginally severe storms are possible over parts
of the Southeast this afternoon into the early evening.

...Southeast this afternoon/evening...
Late morning water-vapor imagery shows a mid-level shortwave trough
moving east across the southern Appalachians. This feature will
reach the VA/NC coast early tonight. Farther northwest, a closed
midlevel low will evolve into an open wave as it moves eastward over
the Great Lakes and OH Valley. An associated surface cold front
will continue to move slowly southeastward from TX to the southern
Appalachians. Isolated to widely scattered thunderstorms will be
possible with the disturbance over the Carolinas this afternoon.
Other than the front pushing into portions of AL/GA, little
larger-scale forcing for ascent is expected farther southwest.
Additional storm development will be associated with the front and
orographic lift along the spine of the Appalachians. Overall
weak-moderate buoyancy, modest deep-layer shear and steepening
low-level lapse rates will support some potential semi-organized
storms capable of producing isolated wind damage and marginally
severe hail for a few hours this afternoon/evening.

...TX through tonight...
--No change needed to previous forecast discussion--
Weak upslope flow along a slow moving cold front will favor
thunderstorm development over the east slopes of the Sierra Madre
Oriental/Sierra del Burro this afternoon, with the potential for a
couple of supercells. However, it is not clear that storm motions
will bring the convection across the Rio Grande, and lingering
convective inhibition suggests storms will likely weaken if they
manage to cross the border. Later tonight in northwest TX, elevated
convection will likely develop atop the frontal surface, in a warm
advection regime downstream from a weak shortwave trough over AZ/NM.
Some small hail may occur given lingering steep midlevel lapse rates
and modest cloud-layer shear, but the potential for severe hail
appears too low to warrant an outlook area.

..Smith/Moore.. 04/19/2024


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