Apr 20, 2014 0600 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  

   NWS STORM PREDICTION CENTER NORMAN OK
   1239 AM CDT SUN APR 20 2014

   VALID 201200Z - 211200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING
   ACROSS PARTS OF THE TEXAS SOUTH PLAINS...

   ...SUMMARY...
   SCATTERED THUNDERSTORMS CAPABLE OF PRODUCING SEVERE HAIL AND A FEW
   STRONG WIND GUSTS ARE POSSIBLE ACROSS THE TEXAS SOUTH PLAINS
   TODAY...MAINLY LATE THIS AFTERNOON INTO EARLY EVENING.

   ...SYNOPSIS...
   MODELS INDICATE THAT LARGE-SCALE UPPER TROUGHING WITHIN THE
   MID-LATITUDE WESTERLIES ACROSS THE EASTERN PACIFIC MAY UNDERGO
   SIGNIFICANT AMPLIFICATION DURING THIS PERIOD AS IT APPROACHES THE
   PACIFIC COAST.  BUT THE WESTERLIES WILL REMAIN SPLIT ACROSS MUCH OF
   THE DOWNSTREAM U.S...WITH ONE ZONAL BRANCH...ACROSS THE NORTHERN
   TIER STATES...REMAINING A BIT STRONGER AND MORE PROGRESSIVE THAN A
   SLIGHTLY MORE AMPLIFIED BUT WEAKER BRANCH ACROSS THE SOUTHERN TIER.

   WITHIN THE SOUTHERN BRANCH...ONE PROMINENT WAVE AND EMBEDDED CLOSED
   LOW APPEARS LIKELY TO CONTINUE SLOWLY EAST OF SOUTH ATLANTIC COASTAL
   AREAS...WHILE ANOTHER WAVE...COMPRISED OF A NUMBER OF SMALLER SCALE
   IMPULSES...GRADUALLY DEVELOPS EAST OF THE SOUTHERN ROCKIES INTO AND
   THROUGH THE SOUTHERN PLAINS.  ALTHOUGH SUBSTANTIAL DRYING HAS
   OCCURRED ACROSS MUCH OF THE GULF OF MEXICO IN THE WAKE OF THE LEAD
   SYSTEM...A NARROW PLUME OF AT LEAST MODEST MOISTURE RETURN IS
   EXPECTED TO CONTINUE...FROM THE SOUTHWESTERN GULF OF MEXICO AND
   MEXICAN GULF COAST AREA THROUGH THE RIO GRANDE VALLEY. 
   MEANWHILE...SEASONABLY WEAK TO MODEST MOISTENING WILL CONTINUE ON
   SOUTHERLY FLOW...AHEAD OF THE LEE SURFACE TROUGH ACROSS THE SOUTHERN
   INTO CENTRAL PLAINS...AND ALONG A STALLING FRONTAL ZONE ASSOCIATED
   WITH A SIGNIFICANT NORTHERN-BRANCH IMPULSE NOW CROSSING ONTARIO.

   THIS MOISTENING...IN THE PRESENCE OF SEASONABLY STEEP LOWER/MID
   TROPOSPHERIC LAPSE RATES...PROBABLY WILL CONTRIBUTE TO SUFFICIENT
   INSTABILITY TO SUPPORT CONSIDERABLE THUNDERSTORM ACTIVITY TODAY AND
   TONIGHT ACROSS THE MIDDLE OF THE COUNTRY.  HOWEVER...THE RISK FOR
   SEVERE STORMS IS EXPECTED TO REMAIN RELATIVELY LOW FOR THE TIME OF
   YEAR.

   ...SOUTHERN PLAINS...
   CONSIDERABLE UNCERTAINTY EXISTS CONCERNING THE EXTENT OF THE
   CONVECTIVE POTENTIAL AS UPPER TROUGHING CONTINUES EAST OF THE
   SOUTHERN ROCKIES TODAY.  A BROAD EMBEDDED CYCLONIC MID-LEVEL
   CIRCULATION...WITH SMALLER SCALE IMPULSES PIVOTING AROUND IT...
   APPEARS LIKELY TO MIGRATE ACROSS THE TEXAS PANHANDLE REGION DURING
   THE AFTERNOON HOURS.  SOME VARIABILITY EXISTS AMONG THE MODELS
   CONCERNING JUST HOW QUICKLY THIS OCCURS.  FURTHERMORE...THE IMPACT
   OF EARLY DAY CONVECTIVE CLOUD COVER AND PRECIPITATION /EXPECTED
   ACROSS PARTS OF THE TEXAS SOUTH PLAINS AND NORTHWEST TEXAS INTO THE
   CENTRAL HIGH PLAINS...AS WELL AS ACROSS PARTS OF CENTRAL AND EASTERN
   NEW MEXICO/ ON DESTABILIZATION ACROSS THE REGION REMAINS UNCLEAR. 
   HOWEVER...AT LEAST A NARROW CORRIDOR OF SUBSTANTIVE BOUNDARY LAYER
   HEATING APPEARS POSSIBLE BETWEEN THESE TWO AREAS BY LATE AFTERNOON. 
   BENEATH THE -14 TO -16C 500 MB COLD CORE OVERSPREADING THE
   REGION...THIS MAY CONTRIBUTE TO MIXED LAYER CAPE UP TO AROUND 1000
   J/KG.

   MID/UPPER FLOW IS FORECAST TO BE RATHER MODEST IN STRENGTH AND
   SOUTHWESTERLY THROUGH MUCH OF THE DAY...RESULTING IN MARGINAL
   VERTICAL SHEAR FOR ORGANIZED CONVECTIVE DEVELOPMENT...AT BEST. 
   HOWEVER...AROUND/SHORTLY AFTER PEAK HEATING...IT APPEARS POSSIBLE
   THAT THE PROGRESSION OF THE CYCLONIC MID-LEVEL CIRCULATION ACROSS
   THE PANHANDLE REGION COULD BE TIMED FAVORABLY TO ALLOW FOR VEERING
   MID/UPPER FLOW TO INCREASE SHEAR SUFFICIENTLY TO ENHANCE STORM
   DEVELOPMENT.  SUPERCELL STRUCTURES MAY NOT BE OUT OF THE
   QUESTION...CONTRIBUTING THE RISK FOR SEVERE HAIL AND WIND GUSTS
   THROUGH EARLY EVENING...PARTICULARLY ACROSS AND EAST/SOUTHEAST OF
   THE PLAINVIEW/LUBBOCK AREA.