Convective Outlook

Day 2 - Storm Prediction Center Norman, Oklahoma

ACUS02 KWNS 211729
SWODY2
SPC AC 211728

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CST Thu Feb 21 2019

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
ARKLATEX TO THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Strong thunderstorms may impact portions of the lower Mississippi
Valley Friday afternoon, into the ArkLaTex vicinity by late Friday
night or early Saturday morning, accompanied by at least some risk
for severe weather.

...Synopsis...

A large-scale upper ridge will remain positioned across the eastern
U.S. on Friday. Further upstream, an intense shortwave trough over
the southwestern states during the morning will shift east and
progressively become negatively tilted as it emerges over the
southern Rockies and southern Plains by 12z Saturday. As this
occurs, Gulf moisture will stream northward through the lower
Mississippi Valley, with 60s dewpoints spreading as far north as
eastern TX into western TN. As the mid/upper trough approaches the
southern Rockies, rapid lee cyclogenesis is expected to ensue during
the evening and overnight hours from far southeast CO into the OK/TX
Panhandle vicinity. Falling heights will beginning to overspread the
southern Plains and Ozark Plateau late in the period, as a
strengthening south/southwesterly low level jet develops from east
TX into the Ozark Plateau.

...Eastern portions of the Southern Plains into the Lower MS
Valley...

A warm front will be draped southwest-northeast from near the Upper
TX Coast to central MS/AL/SC during the morning. Showers and
thunderstorms will likely be ongoing in the vicinity of this
boundary in a warm advection regime. Widespread cloud cover will
limit stronger destabilization in the warm sector, with forecast
MLCAPE values generally less than 750 J/kg during peak heating.
Additionally, forcing for ascent will remain limited for much of the
period, with the warm front being the main focus for stronger storm
development. Furthermore, given the orientation of shear vectors to
the frontal boundary, storms will tend to track toward the cool side
of the boundary. All of these factors will limit stronger,
surface-based convection. However, given favorable effective shear
greater than 40 kt and steepening midlevel lapse rates, should any
pockets of stronger heating occur, or a storm become tied to the
warm front, strong wind gusts and perhaps some marginal hail would
be possible across parts of northern LA into southeast AR and
western MS.

Further west toward east TX, far southeast OK and southwest AR,
severe concerns will remain low for most of the period. After 06z,
increasing forcing for ascent will accompany the arrival of the
mid/upper trough. Stronger height falls and the intensifying low
level jet will result in more favorable conditions for convective
development in the last 3-6 hours of the period. This convection may
remain elevated given the nighttime boundary layer inversion, but
strong deep layer shear will support rotating updrafts and hail
toward Saturday morning. Should any storm become surface based
before then, strong winds also are possible. At this time, despite
improving low level kinematic fields, the tornado threat appears
limited during overnight period given time of day and the elevated
nature of expected convection.

...MAXIMUM RISK BY HAZARD...
Tornado:   2%     - Marginal
Wind:      5%     - Marginal
Hail:      5%     - Marginal

..Leitman.. 02/21/2019

$$