Re: Severe Weather event East Texas / LA / Miss / Ala - April 2 -3 - HIGH Risk - Far East Texas / N LA
Posted: Sun Apr 02, 2017 3:12 pm
New updated graphic by SPC. Still High Risk area.
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Sun Apr 02 2017
Valid 022000Z - 031200Z
...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
NORTHERN LOUISIANA...
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER MUCH OF
LOUISIANA INTO MISSISSIPPI...
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE SABINE
RIVER VALLEY EASTWARD ACROSS THE LOWER MISSISSIPPI VALLEY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE TEXAS
COAST ACROSS THE LOWER MISSISSIPPI RIVER VALLEY...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
SLIGHT RISK AREA...
...SUMMARY...
Widespread severe thunderstorms capable of significant tornadoes,
severe wind, and severe hail will spread from the Sabine river
valley toward the lower Mississippi Valley through tonight. The
greatest risk for tornadoes will exist from across Louisiana into
Mississippi this afternoon through tonight.
...East Texas into Louisiana and western Mississippi...
Storms continue to evolve across the area, with the most intense
cells near the warm front over central LA, and along and just ahead
of the cold front/outflow boundary over far eastern TX. South of
these boundaries, the air mass is very moist and unstable with gusty
southeasterly winds allowing for a gradual northward shift in the
greater instability across LA and into southwest MS. Shear profiles
strongly favor supercells along with tornadoes, with effective SRH
on the order of 400-600 m2/s2 observed on area VAD wind profiles.
The area will continue to experience a severe threat for many more
hours until the cold front moves through from the west. While only a
few of the numerous storms are currently severe, the environment
will remain quite favorable and further intensification of storms is
expected throughout the afternoon and into the evening. For more
information see MCD 403, 404 and 405.
..Jewell.. 04/02/2017
.PREV DISCUSSION... /ISSUED 1127 AM CDT Sun Apr 02 2017/
...Portions of east Texas to the lower Mississippi Valley through
tonight...
A long-lived thunderstorm cluster that crossed central Texas through
the overnight/morning hours is losing organization as it is
advancing into east Texas. Convection continues to form ahead of the
remnant outflow boundary related to the cluster -- from parts of the
Upper TX Coast through the lower Sabine Valley region within a
warm-advection plume. This plume of warm advection is associated
with an amplifying midlevel shortwave trough, whose accompanying
midlevel speed maximum is emerging over south Texas. As the
shortwave trough continues to advance eastward, the low-level mass
response will facilitate poleward return of rich boundary-layer
moisture -- e.g., 15 g/kg mean mixing ratio per Lake Charles 12Z
observed sounding. As such, an expansive warm sector associated with
MLCAPE around 1500-3000 J/kg will become established through the
afternoon from the western/central Gulf Coast northward to a
precipitation-reinforced warm frontal zone forecast to extend from
part of east-central TX eastward across northern Louisiana.
With open-warm-sector convective development now becoming apparent
ahead of the remnants of the convective cluster, it is expected that
this activity will mature as it interacts with the
northward-advancing warm frontal zone. This is where effective SRH
around 300-400 m2/s2 amid strong deep shear and increasing buoyancy
will exist. Given increasing confidence in semi-discrete
supercells/supercell clusters interacting with this warm frontal
zone around peak heating, confidence has increased in greater
tornado potential -- including significant tornadoes -- across the
now-upgraded High Risk area. The significant-tornado potential will
spread toward the lower Mississippi Valley into the evening hours.
Into the evening and overnight hours tonight, a band of warm
advection/confluence will facilitate the development of a
pre-frontal squall line that will advance eastward across parts of
LA/MS and far southern AR. In addition to the potential for
extensive wind damage, meso-vortices and embedded supercells capable
of producing tornadoes are expected to spread eastward through the
lower Mississippi Valley into the overnight hours. Increased
confidence in this scenario warrants eastward extension of the
Moderate Risk area.
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Sun Apr 02 2017
Valid 022000Z - 031200Z
...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
NORTHERN LOUISIANA...
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER MUCH OF
LOUISIANA INTO MISSISSIPPI...
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE SABINE
RIVER VALLEY EASTWARD ACROSS THE LOWER MISSISSIPPI VALLEY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE TEXAS
COAST ACROSS THE LOWER MISSISSIPPI RIVER VALLEY...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
SLIGHT RISK AREA...
...SUMMARY...
Widespread severe thunderstorms capable of significant tornadoes,
severe wind, and severe hail will spread from the Sabine river
valley toward the lower Mississippi Valley through tonight. The
greatest risk for tornadoes will exist from across Louisiana into
Mississippi this afternoon through tonight.
...East Texas into Louisiana and western Mississippi...
Storms continue to evolve across the area, with the most intense
cells near the warm front over central LA, and along and just ahead
of the cold front/outflow boundary over far eastern TX. South of
these boundaries, the air mass is very moist and unstable with gusty
southeasterly winds allowing for a gradual northward shift in the
greater instability across LA and into southwest MS. Shear profiles
strongly favor supercells along with tornadoes, with effective SRH
on the order of 400-600 m2/s2 observed on area VAD wind profiles.
The area will continue to experience a severe threat for many more
hours until the cold front moves through from the west. While only a
few of the numerous storms are currently severe, the environment
will remain quite favorable and further intensification of storms is
expected throughout the afternoon and into the evening. For more
information see MCD 403, 404 and 405.
..Jewell.. 04/02/2017
.PREV DISCUSSION... /ISSUED 1127 AM CDT Sun Apr 02 2017/
...Portions of east Texas to the lower Mississippi Valley through
tonight...
A long-lived thunderstorm cluster that crossed central Texas through
the overnight/morning hours is losing organization as it is
advancing into east Texas. Convection continues to form ahead of the
remnant outflow boundary related to the cluster -- from parts of the
Upper TX Coast through the lower Sabine Valley region within a
warm-advection plume. This plume of warm advection is associated
with an amplifying midlevel shortwave trough, whose accompanying
midlevel speed maximum is emerging over south Texas. As the
shortwave trough continues to advance eastward, the low-level mass
response will facilitate poleward return of rich boundary-layer
moisture -- e.g., 15 g/kg mean mixing ratio per Lake Charles 12Z
observed sounding. As such, an expansive warm sector associated with
MLCAPE around 1500-3000 J/kg will become established through the
afternoon from the western/central Gulf Coast northward to a
precipitation-reinforced warm frontal zone forecast to extend from
part of east-central TX eastward across northern Louisiana.
With open-warm-sector convective development now becoming apparent
ahead of the remnants of the convective cluster, it is expected that
this activity will mature as it interacts with the
northward-advancing warm frontal zone. This is where effective SRH
around 300-400 m2/s2 amid strong deep shear and increasing buoyancy
will exist. Given increasing confidence in semi-discrete
supercells/supercell clusters interacting with this warm frontal
zone around peak heating, confidence has increased in greater
tornado potential -- including significant tornadoes -- across the
now-upgraded High Risk area. The significant-tornado potential will
spread toward the lower Mississippi Valley into the evening hours.
Into the evening and overnight hours tonight, a band of warm
advection/confluence will facilitate the development of a
pre-frontal squall line that will advance eastward across parts of
LA/MS and far southern AR. In addition to the potential for
extensive wind damage, meso-vortices and embedded supercells capable
of producing tornadoes are expected to spread eastward through the
lower Mississippi Valley into the overnight hours. Increased
confidence in this scenario warrants eastward extension of the
Moderate Risk area.
