The SPC is forecasting ...Severe thunderstorms expected over parts of the lower Mississippi Valley region to east Texas today and tonight....   Please read the latest public statement about this event.  View What is a Watch? clip.

   SPC AC 021627

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1127 AM CDT Sun Apr 02 2017

   Valid 021630Z - 031200Z

   ...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   FAR EAST TEXAS AND NORTHERN LOUISIANA...

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   HIGH ACROSS PORTIONS OF EAST TEXAS...NORTHERN AND CENTRAL
   LOUISIANA...CENTRAL AND SOUTHERN MISSISSIPPI...AND EXTREME SOUTHERN
   ARKANSAS...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   MODERATE FROM PORTIONS OF EAST TEXAS TO MISSISSIPPI...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED FROM PORTIONS OF EAST AND SOUTH TEXAS TO FAR WESTERN
   ALABAMA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT FROM EASTERN PORTIONS OF THE SOUTHERN PLAINS TO WESTERN
   ALABAMA...

   ...SUMMARY...
   Widespread severe thunderstorms capable of significant tornadoes,
   severe wind, and severe hail will spread across portions of east
   Texas to the lower Mississippi Valley through tonight. The greatest
   risk for tornadoes will exist from portions of far east Texas
   eastward across northern Louisiana this afternoon and evening.

   ...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.

   ..Cohen.. 04/02/2017

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