SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0243 PM CDT Mon Apr 18 2022
Valid 182000Z - 191200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
SOUTH FLORIDA...AND OVER THE OUTER BANKS OF NORTH CAROLINA...
...SUMMARY...
Isolated severe thunderstorms are possible near the Atlantic Coast
of Florida and the Outer Banks of North Carolina.
Little change was made from the previous outlook, except to reduce
the Marginal Risk area over eastern NC behind the cold front.
Minimal SBCAPE exists except near the Outer Banks, and any isolated
severe risk is expected to end in the next few hours.
Otherwise, heating over southern FL combined with cool midlevel
temperatures may support isolated severe storms along the sea
breeze, with marginal hail or localized damaging gusts.
..Jewell.. 04/18/2022
.PREV DISCUSSION... /ISSUED 1120 AM CDT Mon Apr 18 2022/
...Synopsis...
Mid-morning water vapor imagery and analyses reveal mean troughing
from the Great Lakes into the Mid-Atlantic with a series of embedded
vorticity maxima from the upper MS river valley into the
Mid-Atlantic. A broad swath of cold advection across the Plains into
the Southeast and modest warm advection along the East Coast will
support an amplifying pattern over the next 24 hours. A weak surface
low, currently over the GA/SC coast, will deepen as it lifts to the
north/northeast ahead of the amplifying wave and strengthening
upper-level jet. The surface cold front over the northern Gulf
Coast/Southeast will continue to sweep to the southeast across the
FL peninsula today.
...Coastal Carolinas...
A broad region of stratiform precipitation is ongoing this morning
across much of the Carolinas. This is diabatically reinforcing a
wedge front to the east of the Appalachians where temperatures are
in the 40s to low 50s and instability is negligible (per the 12 UTC
GSO sounding). Along the coast, however, onshore flow is supporting
a shallow marine warm front where temperatures and dewpoints are in
the low to mid 60s. Lapse rates along the coast are slightly steeper
compared to locations inland and may support meager, but sufficient,
instability for convection this afternoon as temperatures gradually
warm under extensive cloud cover. Coastal VWP observations show
strong veering in the lowest 2 km with around 200 m2/s2 0-1 km SRH.
SRH will likely increase through the early to mid afternoon as the
low-level wind fields strengthen in response to the deepening low.
This will continue to support an isolated tornado, and damaging
wind, potential through the afternoon if sufficient instability can
be realized. KMHX imagery over the past 2 hours has shown an
offshore MCV with embedded cells exhibiting organized mesocyclones.
While the offshore thermodynamic environment is more unstable
compared to onshore, this activity may persist into the afternoon as
the MCV glances the NC Outer Banks.
...Southeast Florida...
A growing cumulus field is noted across the southern FL peninsula
where temperatures are already warming into the 80s. Modified 12 UTC
soundings and trends in weak thunderstorm activity suggest any
lingering diurnal inhibition is waning. Surface-based instability
will continue to improve through the early afternoon (upwards of
3000 J/kg by around 21 UTC), and combined with improving upper-level
flow, will support a hail/wind risk as thunderstorms develop along
and ahead of the approaching cold front.
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