SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 PM CDT Fri Mar 18 2022
Valid 182000Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
OHIO AND TENNESSEE VALLEYS INTO SOUTHERN GEORGIA AND THE FLORIDA
PANHANDLE...
...SUMMARY...
Severe thunderstorms are expected through the afternoon and early
evening across portions of the Southeast States where damaging winds
and a couple tornadoes are possible. Additional isolated severe
storms are also possible across parts of the Ohio Valley.
...20z Update...
The Enhanced risk has been removed from FL/GA/AL with the 20z
update. Stronger ascent will continue to shift northeast of the
region, with midlevel subsidence spreading eastward across AL noted
in water vapor imagery. Thunderstorms may continue to develop atop
east/southeast-advancing outflow across southern GA into northern FL
through the remained of the afternoon/early evening in a continued
warm advection regime. This activity may occasionally produce
strong/locally damaging gusts and/or a tornado.
Further north across central/northern AL into Middle TN a
conditional severe threat remains possible. A surface warm front
extends from northeast MS across central AL as of 19z. Surface
dewpoints in the low/mid 60s and clearing skies are aiding in
moderate destabilization with MLCAPE values increasing to around
500-1500 J/kg amid moderate vertical shear. Some deepening CU is
noted in visible satellite imagery and if a few storms develop in
this environment they could pose a threat for strong gusts, hail and
a couple tornadoes. However, this activity will also be fighting
midlevel subsidence and decreasing large-scale ascent. Will maintain
severe probs for a conditional threat as some weak convection is
trying to redevelop across western AL as of 19z.
Across the Ohio Valley, the only changes to the outlook were to trim
the western edge of the Marginal risk based on the current location
of the surface low and ongoing thunderstorm activity.
..Leitman.. 03/18/2022
.PREV DISCUSSION... /ISSUED 1130 AM CDT Fri Mar 18 2022/
...Middle Gulf Coast/Southeast States...
A nearly continuous squall line extends at midday from west-central
Georgia and southeast Alabama, where it is been elevated this
morning, southwestward into far south-central Alabama and the far
western Florida Panhandle. This southwestern-most portion is where
somewhat more broken bands of storms exists and more buoyant
surface-based conducive air resides coincident with dewpoints in the
upper 60s/near 70F.
Heights will tend to rise this afternoon as the richer low-level
moisture otherwise advects east-northeastward toward southeast
Alabama/southwest Georgia. Low-level winds will tend to further veer
and modestly weaken, but nonetheless remain sufficiently strong for
well-organized and rotating storms, which include a tornado and
damaging wind risk.
...Middle Mississippi to Ohio/Tennessee Valleys...
The main forcing for ascent through afternoon will be related to the
northeastward-transition of the mid/upper-level low over the Ozarks
at late morning. Although only modest cloud breaks are noted at
midday, relatively cool mid-level temperatures in conjunction with
50s F dewpoints will be sufficient for modest surface-based
destabilization this afternoon. Arcs of low-topped convection are
anticipated along the northern periphery of this weak surface-based
buoyancy. 30-40 kt effective bulk shear in addition to some
elongation of hodographs should support a few supercells with
mid-level updraft rotation and severe hail as the primary hazard. A
tornado or two may also occur, particularly near the Lower Ohio
Valley portion of the severe risk area.
Farther south, a more conditional severe threat is anticipated in
the wake of the large MCS across the Deep South. Mid-level
subsidence and drying is indicated by most guidance and updrafts
will probably struggle along the cold front sweeping east to the
south of the Missouri cyclone. Guidance may be somewhat overdone
with the degree of boundary-layer moisture return given just how
extensive convective overturning has been this morning in
Mississippi into Alabama/western Tennessee.
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