SPC Apr 21, 2017 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1248 AM CDT Fri Apr 21 2017

Valid 221200Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
MISSISSIPPI...FAR NORTHEAST LOUISIANA AND FAR NORTHWEST ALABAMA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE
SLIGHT RISK AREA IN PARTS OF THE LOWER MISSISSIPPI
VALLEY...TENNESSEE VALLEY...SOUTHERN APPALACHIANS AND CAROLINAS...

...SUMMARY...
Thunderstorms associated with isolated large hail and wind damage
are possible across parts of central and northern Mississippi on
Saturday. Other marginally severe thunderstorms with strong wind
gusts and hail are possible across parts of the Tennessee Valley
eastward into North Carolina.

...Lower Mississippi and Tennessee Valleys...
An upper-level trough will move across the mid Mississippi Valley on
Saturday as a cold front advances southeastward from the Arklatex
into the lower Mississippi Valley. Ahead of the front, a tongue of
low-level moisture will be in place with surface dewpoints into the
60s F across most of Mississippi. This should result in a corridor
of moderate instability extending north northeastward from central
Louisiana into north-central Mississippi by afternoon. Model
forecasts first develop convection in western Tennessee during the
early afternoon on the northern end of the moist tongue with
convection expanding south southwestward across northern and central
Mississippi during the mid to late afternoon. NAM forecast soundings
along this corridor at 21Z show MLCAPE values around 1500 J/kg and
0-6 km shear near 40 kt. This along with steep low-level lapse rates
should be enough for damaging wind gusts with the more organized
multicells. Cells that remain discrete may also rotate and have a
possibility for isolated large hail.

...Southern Appalachians/North Carolina...
West to southwest mid-level flow will be in place on Saturday across
the southern Appalachians and Carolinas. At the surface, a low is
forecast to move across the Tennessee Valley as a cold front
advances southward across North Carolina. Along and just south of
the front, surface dewpoints are forecast to be near 60 F allowing
for a pocket of instability to develop by afternoon. Surface heating
and increased low-level convergence along the front should result in
thunderstorm development by early afternoon. Thunderstorms are
forecast to spread eastward across central and eastern North
Carolina during the mid to late afternoon. NAM forecast soundings in
central North Carolina at 21Z on Saturday show SBCAPE values near
1000 J/kg along with 30 to 40 kt of 0-6 km shear and steep low-level
lapse rates. This could be enough for marginally severe wind gusts
with the stronger multicell storms.

..Broyles.. 04/21/2017

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