419
ACUS01 KWNS 120559
SWODY1
SPC AC 120557

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1257 AM CDT Sun May 12 2024

Valid 121200Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EAST TX INTO
WESTERN/CENTRAL LA...

...SUMMARY...
Scattered strong to severe storms are possible later today and
tonight from east Texas into western and central Louisiana. Large
hail, locally damaging winds, and a couple tornadoes will be
possible. More isolated strong to severe storms will be possible
across parts of the central and southern High Plains into central
Texas, and also near the upper Great Lakes region.

...Synopsis...
A positively tilted mid/upper-level trough will move eastward from
the southern Rockies towards the southern Great Plains through the
day. A weak surface low may become established across the southern
High Plains, within a broader surface trough. A surface boundary
across TX will try to move northward as a warm front, though
persistent convection could limit its progress through the forecast
period.

Farther north, a deep-layer cyclone will move across northern
Ontario, with the southern portion of this system affecting parts of
the upper Great Lakes through the day. A cold front attendant to
this system will move across the northern Great Plains into parts of
MN/WI.

...Central/east TX into the lower MS Valley...
A front draped from central TX into LA will separate very rich
low-level moisture to the south from a cooler and more modestly
moist airmass to the north. Convection may increase in coverage
along/north of the front through the morning, within a low-level
warm advection regime. Initial development will likely be elevated
north of the front, though moderate buoyancy and sufficient
deep-layer shear could still support a supercell or two with a
threat of large hail and locally gusty winds.

Stronger heating/destabilization south of the front may eventually
support surface-based storm development near the boundary,
potentially from south-central into southeast TX. Rich low-level
moisture, moderate to strong buoyancy, and sufficient deep-layer
shear will support the potential for a few supercells.

There may be a tendency for convection to organize into clusters,
with some potential for embedded cells to become slightly undercut
by the outflow-reinforced front over time. However, low-level
shear/SRH will be more than sufficient for a tornado threat with any
supercell that can remain surface-based. A 5% tornado probability
area has been introduced, though some adjustment of its position may
be required depending on trends regarding the frontal location later
today. Hail and damaging wind will also be possible, with a
conditional risk for very large hail if cells can remain discrete.

There will be some potential for a forward-propagating cluster to
move east-southeastward toward the lower MS Valley later tonight,
though the inland advance of the front with time and eastward extent
remains uncertain.

...Parts of the southern/central High Plains...
While richer moisture will stay confined to central/south TX, a
narrow corridor of moderate destabilization will be possible along
the surface trough/effective dryline from the TX South Plains
vicinity northward into western KS.

Greater storm coverage is expected across the northern portion of
this corridor across western KS, in closer proximity to the primary
mid/upper-level trough. Cool temperatures aloft and steep lapse
rates will support a hail threat with the strongest storms. However,
with weak low-level flow and only modest deep-layer shear,
convection may only be weakly organized.

Deep-layer flow/shear will increase southward along the dryline into
the OK/TX Panhandles and the TX South Plains. Isolated supercell
development will be possible along the dryline during the afternoon,
with an attendant threat of hail and locally gusty winds. The
longevity of any supercells may be relatively limited, due to the
limited width of the best instability corridor. There is some chance
for a longer-lived supercell to develop near the front/dryline
intersection somewhere across the TX Big Country, and then propagate
southeastward along the instability gradient. However, the boundary
position and most favored corridor for such a scenario remain
uncertain at this time.

...Upper Great Lakes vicinity...
Moisture will likely remain rather limited across the upper Great
Lakes vicinity in advance of the cold front, However, strong heating
will support some destabilization, with MLCAPE potentially
increasing into the 500-1000 J/kg range. Moderate west-northwesterly
midlevel flow will support some potential for organized convection,
and a few stronger cells/clusters may pose a threat for localized
severe gusts and perhaps some hail this afternoon and evening.

..Dean/Squitieri.. 05/12/2024

$$