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Apr 21, 2015 1730 UTC Day 2 Convective Outlook
Updated: Tue Apr 21 17:30:57 UTC 2015 (Print Version | 20150421 1730Z Day 2 shapefile | 20150421 1730Z Day 2 KML)
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 Forecast Discussion

   SPC AC 211730

   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1230 PM CDT TUE APR 21 2015

   VALID 221200Z - 231200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS OVER A PORTION OF SRN OK
   THROUGH NRN TX AND NRN LA...

   ...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE SRN
   PLAINS AND LOWER MS VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER A PORTION OF THE SRN
   PLAINS AND LOWER MS VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER A PORTION OF THE MID
   ATLANTIC...

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER A PORTION OF SRN FL...

   ...SUMMARY...
   THUNDERSTORMS WITH WIND DAMAGE...LARGE HAIL AND POSSIBLY A FEW
   TORNADOES ARE EXPECTED TO DEVELOP WEDNESDAY FROM THE SOUTHERN PLAINS
   EASTWARD ACROSS THE ARKLATEX AND THE LOWER MISSISSIPPI VALLEY.
   ISOLATED STORMS WITH HAIL AND WIND DAMAGE ARE POSSIBLE OVER SOUTH
   CENTRAL TEXAS INTO THE TEXAS COASTAL PLAINS. OTHER THUNDERSTORMS MAY
   DEVELOP OVER THE MIDDLE ATLANTIC REGION AND THESE COULD PRODUCE
   LOCALLY STRONG WIND GUSTS. GENERAL THUNDERSTORM ARE EXPECTED ACROSS
   PARTS OF THE CENTRAL TO NORTHERN ROCKIES AND SIERRA NEVADA AREAS.

   ...SYNOPSIS...

   A SPLIT FLOW...BLOCKING SYNOPTIC REGIME WILL PERSIST WEDNESDAY WITH
   A LARGE UPPER TROUGH OVER THE ERN STATES...A CUTOFF LOW OVER SRN CA
   AND AN UPPER RIDGE OVER THE NRN ROCKIES THAT WILL BE SUPPRESSED BY A
   NRN STREAM SHORTWAVE TROUGH NOW APPROACHING THE PACIFIC NW. AT THE
   SFC A COLD FRONT WILL MOVE THROUGH THE NERN STATES AND MIDDLE
   ATLANTIC AREA THEN SWWD INTO THE SRN PLAINS WHERE IT WILL LIKELY
   STALL NEAR THE RED RIVER AREA ALONG THE TX/OK BORDER. DRYLINE WILL
   ALSO SHARPEN ACROSS WRN TX.

   ...SRN PLAINS THROUGH LOWER MS VALLEY AREA...

   MODIFYING GULF AIR WILL RETURN THROUGH THE PRE-FRONTAL WARM SECTOR
   WITH NEAR SFC DEWPOINTS RISING TO LOW 60S OVER EXTREME SRN OK TO LOW
   70S IN SOUTH TX BENEATH PLUME OF STEEP LAPSE RATES RESULTING IN
   2000-3000 J/KG MLCAPE AS DIABATIC HEATING COMMENCES. IT IS LIKELY
   THAT A FEW ELEVATED THUNDERSTORMS WILL BE ONGOING WITHIN ZONE OF
   ISENTROPIC ASCENT ALONG AND NORTH OF FRONT ACROSS WRN/NRN OK EARLY
   WEDNESDAY MORNING. UPPER PATTERN OVER THIS REGION WILL BE DOMINATED
   BY LOW-AMPLITUDE SHORTWAVE RIDGING DURING THE DAY WITH WEAK FORCING
   ALOFT. HOWEVER...MESOSCALE FORCING IN VICINITY OF THE FRONT AS WELL
   AS THE FRONT-DRYLINE INTERSECTION SHOULD PROVIDE A FOCUS FOR STORMS
   TO DEVELOP AS THE BOUNDARY LAYER DESTABILIZES. IT IS ALSO POSSIBLE
   THAT SOME OF THE EARLY STORMS COULD BECOME SURFACE BASED AS THEY
   DEVELOP SEWD THROUGH CNTRL/SRN OK. EFFECTIVE BULK SHEAR WILL SUPPORT
   ORGANIZED STORM STRUCTURES INCLUDING SUPERCELLS...BUT SOME OF THE
   STORMS MAY EVOLVE INTO ONE OR MORE CLUSTERS AS THEY DEVELOP SEWD
   THROUGH ERN TX INTO THE LOWER MS VALLEY WITH POTENTIAL FOR BOWING
   SEGMENTS. LARGE HAIL AND DAMAGING WIND WILL BE THE MAIN
   THREATS...BUT A FEW TORNADOES ARE ALSO POSSIBLE. SURFACE BASED
   THUNDERSTORM INITIATION OVER SRN TX IS MORE UNCERTAIN GIVEN LACK OF
   LOW-LEVEL FOCUS AND POTENTIAL CAPPING ISSUES...BUT A FEW STORMS MAY
   DEVELOP OVER THE HIGHER TERRAIN OF NRN MEXICO AND CROSS INTO SRN TX.


   ...MID ATLANTIC AREA...

   VERY LIMITED LOW-LEVEL MOISTURE IN WARM SECTOR WILL BE COMPENSATED
   FOR BY COLD AIR ALOFT...STEEP LAPSE RATES AND DIABATIC WARMING TO
   RESULT IN WEAK MLCAPE /AOB 300 J/KG/. UPPER JET EMBEDDED WITHIN
   UPPER LOW CIRCULATION WILL AUGMENT FORCING ALONG AND AHEAD OF FRONT
   AND LIKELY PROMOTE THE DEVELOPMENT OF HIGH BASED CONVECTION. THIS
   ACTIVITY WILL RESIDE WITHIN STRONG WLY DEEP-LAYER WINDS WITH
   INVERTED-V BOUNDARY LAYERS SUGGESTING ISOLATED CONVECTIVELY ENHANCED
   GUSTS WILL BE POSSIBLE.

   ..DIAL.. 04/21/2015

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Page last modified: April 21, 2015
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