acus01 kwns 292002
Storm Prediction Center ac 292000
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0300 PM CDT Wed Mar 29 2017
Valid 292000z - 301200z
..there is an enhanced risk of severe thunderstorms for the
Missouri and Arkansas Ozarks...
..there is an enhanced risk of severe thunderstorms for southeast
Texas northeast into the lower Mississippi Valley...
..there is a slight risk of severe thunderstorms for East Texas and
lower Mississippi Valley and Ozark Plateau...
..there is a marginal risk of severe thunderstorms surrounding the
Severe thunderstorms are expected this afternoon into tonight from
parts of East Texas, eastern Oklahoma, and southeast Kansas into the
lower and middle Mississippi Valley. Large hail, tornadoes, and
damaging winds will be possible especially later this afternoon and
The biggest substantial changes have been dictated in part to
upper-air raob data from lzk (19z raob) and short-term model trends
(time-lagged hrrr model). Have confined the 10-percent tornado to
the Ozarks and in a corridor from the lower Sabine valley
northeastward into northeastern la and far west-central MS. Have
removed the significant tornado delineation based on instability
concerns and prior convective overturning earlier today and recent
surface analysis displaying a slower-than-expected recovery.
Previous discussion... /issued 1147 am CDT Wed Mar 29 2017/
..Ozarks/lower MO valley to arklatex/lower MS River Valley...
The closed upper trough currently over the south-Central Plains at
late morning will continue a slow-general-northeastward advance
toward the lower MO River Valley through late tonight and early
Thursday. Ahead of this system, 12z regional observed soundings
reflected considerable lapse-rate-related impacts from the
overnight/early morning squall line that continues to move generally
east-northeastward and decay across the Ozarks and Ark-la-tex
vicinity. This may have ramifications on the
extensiveness/likelihood of significant hail potential, for
instance, although the air mass will recover/gradually moisten and
destabilize to the south of a northward-moving warm front across the
Ozarks/lower MO valley, and ahead (east) of a slow-eastward-moving
Latest thinking is that surface-based storms will develop as early
as mid-afternoon near the eastern Kansas surface low southward along the
front, including far eastern portions of Kansas/OK into western portions
of MO/AR. Moderate low-level hodograph curvature (beneath strong but
somewhat backed mid-level southwesterly winds) and resultant strong
low-level shear/srh will support a tornado risk aside from large
hail and evolving damaging wind risk into this evening.
Farther south, storms may diurnally be a bit more isolated across
the remainder of the arklatex vicinity, although an ongoing
quasi-linear cluster across near-coastal southeast Texas may persist
east-northeastward into la as it favors a zone of outflow-related
weak boundary/zone of differential heating. This cluster and other
peripheral development may pose a damaging wind/tornado risk through
the afternoon and evening hours.
Later tonight, storms should increase in coverage/intensity
initially across portions of Arkansas/la as forcing for ascent/DPVA
increases related to an east/northeastward-ejecting vorticity maxima
within the base of the larger-scale trough. Related mass response
should result in increasingly strong low-level winds/confluence. A
mixed Mode of storms should be prevalent, with hail initially
possible prior to a more common damaging wind/embedded tornado risk
as storms toward/across the MS river late tonight.
acus11 kwns 292251
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 292250
Mesoscale discussion 0370
National Weather Service Storm Prediction Center Norman OK
0550 PM CDT Wed Mar 29 2017
Areas affected...portions of la...western MS...southeast Arkansas
Concerning...Tornado Watch 98...
Valid 292250z - 300045z
The severe weather threat for Tornado Watch 98 continues.
Summary...the risk for severe thunderstorms and tornadoes continues
across Tornado Watch 98, and will spread east-northeastward and
northeastward through the evening and overnight hours. An additional
watch will likely be required prior to the 02z expiration of watch
Discussion...clusters of thunderstorms, including embedded rotating
updrafts and bowing segments, continue in the vicinity of the lower
Sabine valley. Inflow for this activity is characterized by around
500-2000 j/kg of MLCAPE (higher buoyancy amid Richer moisture with
southward extent), based on modifications to the 18z Lake Charles
and Shreveport observed soundings. This activity lies within the
warm sector of a broader extratropical cyclone, within which modest
positive Theta-E advection will continue during the next several
As a result, convection will continue to spread east-northeastward
and northeastward into the evening and overnight hours. This will
occur while ascent attendant to the right-entrance region of a
midlevel speed maximum encourages both (1) the maintenance of at
least modest instability, and (2) a low-level mass response
supporting moderate low-level shear and isentropic ascent. Moreover,
with 40-55 kt of effective shear attendant to the speed maximum,
organized convective modes will continue to be favored.
While damaging winds and sporadic severe hail will be the primary
concerns with this activity, tornado potential will exist with
embedded supercell structures and meso-vortices. This would
especially be the case as strengthening low-level shear juxtaposes
increasing boundary-layer Theta-E through the night. Accordingly, a
new watch will likely be issued from parts of southern la to the
arklamiss region prior to the expiration of Tornado Watch 98.
..please see www.Spc.NOAA.Gov for graphic product...
Latitude...Lon 31839094 30869140 29849232 29729387 30009428 30459432
31519353 33199273 33959204 34029100 33249064 31839094