SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Wed Apr 13 2022
Valid 132000Z - 141200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHEASTERN MISSOURI...SOUTHERN ILLINOIS...WESTERN
KENTUCKY...WESTERN TENNESSEE...EASTERN ARKANSAS...NORTHEASTERN
LOUISIANA...AND NORTHERN MISSISSIPPI...
...SUMMARY...
Numerous severe thunderstorms are expected this afternoon and
evening across the Mid-South, lower/middle Mississippi Valley, and
Lower Ohio Valley. Tornadoes, some of which will be strong, along
with widespread and potentially significant damaging wind gusts and
large hail, remain likely especially within the Moderate and
Enhanced Risk areas.
...Discussion...
Few changes appear necessary to the ongoing outlook at this time,
aside from trimming western fringes of thunder and severe-risk areas
due to progression of the surface front and associated/ongoing
convection.
Along with a couple of loosely organized bands of strong to severe
storms ongoing from southeastern Missouri to East Texas, development
of anticipated/more isolated storms ahead of the line appears to be
occurring now over the northern Louisiana vicinity. These storms --
should continued development indeed occur -- would likely be
accompanied by more substantial tornado potential over the next few
hours. Otherwise, risk for several -- potentially strong --
tornadoes, along with strong/damaging winds and large hail -- remain
likely through this afternoon and evening, and into the overnight
hours mainly across the central Gulf Coast area.
..Goss.. 04/13/2022
.PREV DISCUSSION... /ISSUED 1126 AM CDT Wed Apr 13 2022/
...Synopsis...
An upper-level trough over the OK/TX Panhandle this morning will
become negatively tilted as it amplifies and shifts northeastward
through the day today and into the Great Lakes tonight. This will
deepen the surface low across the Upper Midwest and tighten the
frontal boundary from northern Illinois to eastern Texas this
afternoon and accelerate the front east to the western Appalachians
by Thursday morning.
...Lower Ohio Valley into the Lower/Mid Mississippi Valley...
Convection this morning will have significant ramifications on the
severe weather risk throughout the day. Thunderstorms have formed
along and ahead of the cold front from southern Missouri across
Arkansas and into northeast Texas. This front (or convectively
enhanced effective front) should mark the northwestern periphery of
the severe weather threat today. East of this front, widespread
convection has also developed across eastern Missouri and into
Illinois in the uncapped airmass sampled by the 12Z ILX RAOB.
Continued convection through the morning and early afternoon across
this region will likely limit destabilization and northward moisture
transport, stunting storm intensity with northern extent.
Farther south, a significant severe weather threat remains. An EML
across this region (sampled by the KLZK 12Z RAOB) should permit more
robust low-level heating. Currently there is a drier surface airmass
in this region in the wake of the morning MCV which has since moved
into central Kentucky. However, northward low-level moisture
advection is already underway with mid 60s dewpoints into southern
Arkansas and upper 60s dewpoints in Louisiana and southern
Mississippi.
The severe weather threat across this region will be bi-modal. The
organizing squall line from the Ozarks to northeast Texas will
accelerate east during the afternoon/evening hours. This will pose a
threat for both damaging winds and QLCS/embedded supercell
tornadoes. Additional convection is expected to develop ahead of
this line during peak heating. This activity will likely pose the
greatest strong tornado threat with the potential for an intense
tornado or two. Forecast hodographs show the majority of the shear
in the lowest 1.5 km with nearly uniform flow in the cloud bearing
layer. This may reduce hydrometeor venting in the mid-upper levels
and result in messier updrafts and HP supercell mode. This could
partially explain the strong, but shorter track, updraft helicity
swaths shown by most 12Z CAM guidance. However, despite this, some
longer track storms are likely across southeast Arkansas and
northwestern Mississippi where greater low-level moisture and
instability is forecast.
The severe threat will gradually reduce with southern extent where
mid-level flow will be weaker and low-level flow will veer as the
upper trough moves away.
...Portions of the Northeast...
Isolated strong to severe storms may occur from western
Maryland/eastern West Virginia across Pennsylvania and into central
New York. Limited moisture will keep instability on the lower side,
but enough heating is forecast for MLCAPE in the 500 to 750 J/kg
range with supercell wind profiles. Therefore, occasional weakly
rotating updrafts could produce marginally severe hail/damaging wind
gusts across the region.
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