Severe Storm Outlook Narrative (AC)
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000
ACUS02 KWNS 121735
SWODY2
SPC AC 121733

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1233 PM CDT Tue Mar 12 2024

Valid 131200Z - 141200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR THE LOWER
MISSOURI VALLEY...

...SUMMARY...
Severe thunderstorms capable of large to very large hail and a
tornado or two are possible across the Lower Missouri Valley from
Wednesday afternoon through Wednesday night.

...Synopsis...
A large-scale upper trough will amplify over the Interior West
during the period with a downstream ridge over the MS Valley
shifting east into the OH Valley/Appalachians.  A shortwave trough
is forecast to eject northeast from the Sangre de Cristos into the
lower MO Valley through the mid evening.  A belt of stronger mid to
upper-level southwesterly flow will overspread the TX Panhandle and
OK during the afternoon and eventually nose into the lower MO Valley
overnight.  In the low levels, a cyclone over the KS vicinity during
much of the day 2 period will feature a warm front advancing north
through portions of the lower MO Valley and a dryline extending
southward into OK and north TX.

...KS and NE eastward into the mid MS Valley...
Strong low-level moisture advection into the region will occur as
surface dewpoints are forecast to rise into the 50s deg F.
Large-scale ascent attendant to the approaching shortwave trough
coupled with low-level convergence near the surface low and warm
front are expected to provide the lift needed for convective
initiation. Storm coverage prior to sunset remains uncertain but
thunderstorm coverage will likely increase during the evening near
the warm front over northern KS eastward into the northern half of
MO during the evening into the overnight.  Steep mid-level lapse
rates and strong deep-layer shear will support a storm environment
in which the stronger storms will be capable of large to very large
hail.  If moisture quality is locally higher near the warm frontal
zone and a supercellular mode is maintained, a tornado risk could
develop due to enlarged hodographs.  Storm coverage will likely
increase into the overnight as warm-air advection strengthens in
tandem with a LLJ.  Primarily elevated storms capable of a
large-hail threat may extend as far east as northeast MO into
west-central IL.

...OK and north TX...
Greater uncertainty on thunderstorm development will exist southward
along the dryline and into eastern portions of OK and perhaps north
TX beginning late Wednesday afternoon into Wednesday night.  Model
guidance varies considerably on the magnitude of low-level moisture
with NAM exhibiting a more moisture-rich setup compared to model
ensembles (HREF, SREF) and considerably drier solutions like the 15z
RAP and latest GFS.  Forecaster experience with these early season
moisture return setups suggest a median to slightly drier solution
is most probable.  Moisture is the primary and likely consequential
ingredient that will dictate severe thunderstorm risk across this
corridor late Wednesday afternoon into the evening.  With those
concerns stated, cool mid-level temperatures in the -16 to -17 deg C
range will result in steep lapse rates and contribute to moderate
buoyancy (MLCAPE 1000-2000 J/kg).  Clockwise-curved and elongated
hodographs would favor supercells if a sustained storm can root in
the boundary layer.  Given the low probability (currently depicted
in ensemble CAM guidance) for storm development, will maintain a
categorical 1 (Marginal) risk.

..Smith.. 03/12/2024

$$


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