Updated:Â Sun Apr 12 20:07:40 UTC 2020
Day 1 RiskArea (sq. mi.)Area Pop.Some Larger Population Centers in Risk AreaMODERATE82,57910,522,727Atlanta, GA...Birmingham, AL...Montgomery, AL...Columbus, GA...Jackson, MS...ENHANCED174,86119,181,305Charlotte, NC...Nashville, TN...Shreveport, LA...Mobile, AL...Knoxville, TN...SLIGHT261,57031,438,568Dallas, TX...Memphis, TN...New Orleans, LA...Tulsa, OK...Raleigh, NC...MARGINAL210,84525,021,363Jacksonville, FL...Columbus, OH...Fort Worth, TX...Oklahoma City, OK...Kansas City, MO...
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0307 PM CDT Sun Apr 12 2020
Valid 122000Z - 131200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM A PORTION
OF MISSISSIPPI MUCH OF ALABAMA INTO WESTERN AND CENTRAL GEORGIA...
...SUMMARY...
An outbreak of severe thunderstorms is likely through tonight, with
the greatest threat expected across parts of Mississippi, Alabama
and Georgia. Strong tornadoes, widespread damaging winds, and large
hail are all possible.
...Southeast States...
Primary change to current outlook has been to trim back on
northwestern portion of the MDT and ENH across TN and northwestern
MS. Widespread stratiform precipitation in this region is limiting
destabilization potential. Otherwise, primary tornado and damaging
wind threat is expected to evolve this afternoon into tonight from
MS, AL into GA with storms developing along warm conveyor belt
associated with an intense low-level jet. Activity will reach the
Carolinas late tonight. Damaging wind and tornadoes, some of which
could be strong, are the primary threats.
..Dial.. 04/12/2020
.PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Apr 12 2020/
...Synopsis...
A complex forecast with multiple scenarios possible across a
broad area from the Lower MS Valley into the TN/OH Valleys and the
Southeast. A compact shortwave trough over the Edwards Plateau of TX
will accelerate east-northeast into the Ark-La-Miss by this evening
and towards eastern KY/TN by the end of the period, in response to
continued amplification of a large-scale trough over the
north-central states.
...Northwest LA to northern AL/middle TN...
An ongoing MCS with a history of several confirmed but brief TDSs
earlier this morning will continue to move east-northeast along an
intensifying baroclinic zone across parts of northern/central MS
into northern AL/middle TN. Tornadoes and damaging winds will be
likely with this MCS which will include a mixed convective mode of
bowing segments and potential supercells developing just ahead of
the cluster on its southern flank.
The presence of upper 60s to low 70s surface dew points in much of
LA and southern MS will spread north and likely reach northern MS to
western AL between 21-00Z. This should overlap strong low-level
shear (0-1 km SRH of 400+ m2/s2) as the low-level jet strengthens
and shifts northeast. The environment will favor embedded supercells
capable of producing strong tornadoes and damaging winds, the most
substantial of which may occur from northeast LA through
north-central MS into northern AL and southern middle TN. There is
still enough uncertainty with regard to convection outpacing
stronger surface-based instability (especially with northeast
extent), as well as the overall convective mode, to preclude an
upgrade to High Risk.
...Southern MS to GA/Carolinas...
To the south of the initial MCS crossing northern MS/AL into TN, a
separate pre-frontal band of convection is expected to become
sustained by early evening from southern MS into central AL. This
convection will be well east of the synoptic cold front, in an
environment with moderate surface-based buoyancy and very strong
vertical shear. A broken band of embedded supercells appears likely
to develop through the evening and overnight, with an associated
threat for strong tornadoes and damaging winds. The pre-frontal
convection should reach the western Carolinas by 09-12z.
...Lower Red River Valley to the OH Valley...
An arc of convection will likely form later this afternoon just
ahead of the compact shortwave trough and associated surface cyclone
in eastern OK to northeast TX, within the left-exit region of the
mid-upper jet. This convection will subsequently spread east then
northeast across the Mid-South during the late afternoon/evening.
The northward extent of destabilization in AR/western TN this
afternoon/evening will depend largely on the intensity and extent of
the early-day MCS moving from LA into northern MS.
Still, steep midlevel lapse rates with the ejecting mid-level wave
and strong deep-layer vertical shear will favor fast-moving
supercells and line segments capable of producing large hail and
damaging winds. The northeast extent of the damaging wind and
tornado threat into tonight will depend largely on how
widespread/organized the convection is across northern MS/AL this
afternoon/evening, and the degree of low-level recovery in the wake
of that convection.