RSS Mesoscale Discussions from Storm Prediction Center
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0741 AM CDT Wed Mar 11 2026
Valid 111300Z - 121200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
MISSISSIPPI VALLEY ACROSS THE TENNESSEE AND OHIO VALLEYS INTO THE
MID-ATLANTIC...
...SUMMARY...
Isolated to scattered severe thunderstorms are expected today from
the ArkLaTex and Lower Mississippi Valley northeastward through the
Ohio Valley and Mid-Atlantic.
...Synopsis...
Split-flow upper pattern persists across the CONUS this morning,
with an upper low moving through TX in the southern stream and a
shortwave trough moving through the northern and central Plains
within the northern stream. Both of these systems are forecast to
progress quickly eastward amid modest phasing and trend towards a
more confluent, single-stream pattern by early tomorrow morning.
Currently a broad region of moderate to strong low/mid-level flow
extends from TX northeastward into eastern Ontario/southern Quebec.
The strongest low-level flow with this broad region is over the
Lower/Middle Ohio Valley, where 850 mb flow is around 50 to 60 kt.
Thunderstorms are currently clustered over two areas within this
broader region, IL and OH, and farther south from east TX into the
Arklatex. The greatest severe thunderstorm potential is expected to
concentrate downstream of the areas today, with damaging gusts as
the primary severe hazards.
...Ohio Valley through the Mid-Atlantic...
Regional radar imagery shows a convective line extending from
west-central IN southwestward into southern IL. This line is
progressing quickly east-northeastward and has produced several
strong gusts (i.e. 40-45 kt) thus far. Regional radar imagery also
depicts a MCV moving into southern IL. Mesoscale ascent attendant to
this MCV could be aiding in the development of the convective line
as well as the more cellular storms to its south. General
expectation is for this convective line to continue quickly
northeastward across the Ohio Valley, with the robust low-level flow
support in the potential strong to severe gusts as well as a few
line-embedded tornadoes. This activity will spread east toward the
Middle Atlantic by late afternoon.
This ongoing line is well ahead of a shortwave trough moving through
the northern/central Plains, and strong low-level moisture advection
will likely result in airmass recovery in its wake ahead of the
shortwave. As a result, a second round of thunderstorms is
anticipated as the shortwave and its associated cold front moves
through the Ohio Valley during the afternoon and evening. Despite
airmass recovery, the overall buoyancy will likely be tempered by
widespread clouds and muted diurnal heating. Even so, the
combination of modest buoyancy with robust shear will still support
another round of strong to severe thunderstorms. Strong gusts are
the primary risk, but line-embedded tornadoes are possible as well.
Any mature discrete development ahead of the front would likely be
supercellular and capable of all severe hazards, including
tornadoes.
...East Texas through the Southeast...
A few strong to severe thunderstorms are currently ongoing within a
broad area of precipitation from east TX into southern AR, supported
by modest buoyancy and strong vertical shear downstream of a
shortwave moving through west TX. As mentioned in recently issued
MCD 211, some weakening and veering of low-level flow has been noted
in regional VWPs, but deep-layer shear remains favorable, and
seasonably rich low-level moisture will continue to support moderate
buoyancy. The severe threat may tend to remain rather isolated in
the short term, though the strongest cells/clusters will be capable
of producing locally damaging wind and perhaps a tornado.
A more substantial increase in the coverage of the severe threat is
expected later this afternoon, in response to increased ascent
attendant to the approaching shortwave trough. This additional
development will likely begin in a more cellular mode over east TX
before progressing eastward and becoming more linear with time. All
hazards are possible with this more cellular activity, including
tornadoes. Southwesterly flow aloft should strengthen ahead of the
shortwave throughout the evening and overnight, leading to increased
organization and strength of the convective line. As such, the
threat for damaging gusts and line-embedded tornadoes will persist
throughout the night across the Gulf Coast states.
..Mosier/Dean.. 03/11/2026
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