SPC AC 261236
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0736 AM CDT Sun Mar 26 2023
Valid 261300Z - 271200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS CENTRAL LA TO
CENTRAL/SOUTHERN AL...
...SUMMARY...
Episodic severe thunderstorms will persist through at least this
evening across a large swath of the Southeast States. A few strong
tornadoes and very large hail should accompany the most intense
storms, particularly from central Louisiana across central to
southern portions of Mississippi and Alabama.
...Southeast...
Multiple rounds of severe thunderstorms are anticipated this morning
through at least this evening, before likely waning overnight.
Round one will be associated with a mix of supercells and clusters
near a quasi-stationary front through central portions of AL/GA. The
leading portion of this activity will likely consolidate and grow
upscale into a forward-propagating MCS across the Savannah Valley to
the coastal Carolinas before it progresses offshore in the early
afternoon. Pervasive warm-sector cloud cover should slow
boundary-layer heating and may limit a more widespread severe wind
threat. Nevertheless, ample buoyancy with MLCAPE of 1500-2000 J/kg
and around 50-kt effective bulk shear will support potential for a
couple tornadoes, along with a mix of large hail and damaging winds.
In the wake of this leading activity, weak low-level isentropic
ascent should persist across residual composite front/outflow. This
should be sufficient to sustain regenerative supercell development
focused on central AL, while warm-sector low-level confluence will
probably support scattered storms emanating from the central Gulf
Coast. With upper 60s to low 70s surface dew points common across
this region, even limited boundary-layer heating will support a
persistent severe threat. However, bulk of guidance suggests
low-level hodograph curvature within the warm sector should remain
modest until this evening, lowering confidence in a more substantial
tornado threat through mid-afternoon.
A third corridor of significant severe potential should evolve
across the Sabine to Lower MS Valleys this afternoon and evening.
Below-average confidence exists in more specific timing this
afternoon given the large spread in guidance with handling the
initially weak forcing for ascent via low-level warm advection. Even
so, low-level wind fields will strengthen into late afternoon in
response to a shortwave trough ejecting from the Southwest to the
Mid-MS Valley. This should support peak tornado potential during the
late afternoon to early evening, particularly where semi-discrete
supercells can become anchored along pre-existing outflow boundaries
as the largest buoyancy today is expected to develop across
southeast LA and southern MS. The setup will support potential for a
few intense supercells capable of strong tornadoes and very large
hail. With time, convection should consolidate into at least a small
MCS, propagating eastward along the composite front/large-scale
outflow this evening with a mix of all hazards anticipated.
...IL/IN...
Low-topped thunderstorms should develop this afternoon across
eastern IL as a low-amplitude shortwave trough overspreads this
region. Although low-level moisture should remain limited, enough
weak instability should still develop through the day as mid-level
temperatures cool with the shortwave trough passage. With some
enhanced low/mid-level flow forecast, any convection that can
develop and be sustained may pose an isolated damaging wind risk.
..Grams/Goss.. 03/26/2023
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