Mar 27, 2009 1300 UTC Day 1 Convective Outlook
Updated: Fri Mar 27 12:38:21 UTC 2009
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the southern plains and central gulf coast states through tonight....  

Categorical Graphic
20090327 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20090327 1300 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20090327 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20090327 1300 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 271223
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0723 AM CDT FRI MAR 27 2009
   
   VALID 271300Z - 281200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER FAR NERN TX...NRN LA...SRN
   AR...CENTRAL MS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE SRN PLAINS
   ACROSS THE CENTRAL GULF COAST STATES...
   
   ...SRN PLAINS ACROSS LOWER MS VALLEY/CNTRL GULF COAST STATES...
   INTENSE MID/UPPER LEVEL LOW DIGGING SSEWD ACROSS CO/NRN NM EARLY
   THIS MORNING WILL BEGIN TO TURN MORE ELY BY LATE TODAY AS 100+ KT
   MID LEVEL JET BEGINS TO ROTATE THROUGH BASE OF TROUGH.  ASSOCIATED
   SURFACE LOW NOW DEEPENING OVER NWRN TX WILL LIKEWISE DEVELOP ENEWD
   ACROSS THE ARKLATEX REGION BY THE EARLY EVENING AND INTO THE MID
   SOUTH OVERNIGHT.  COMPLEX WARM SECTOR IS IN PLACE AHEAD OF THIS
   INTENSE SPRING-TIME SYSTEM DUE TO EXTENSIVE CONVECTION THURSDAY AND
   ASSOCIATED OUTFLOW BOUNDARY EXTENDING ALONG THE CENTRAL GULF COAST
   INTO DEEP SOUTH TX.  RICHEST GULF MOISTURE IS BEING CONTAINED SOUTH
   OF THIS FEATURE EARLY THIS MORNING.  HOWEVER AS PRESSURE FALLS
   INCREASE OVER ERN PORTIONS OF THE SRN PLAINS...EXPECT GRADUAL
   RECOVERY/NWD ADVECTION OF RICHER GULF MOISTURE THROUGH THE
   DAY...ESPECIALLY OVER ERN TX/WRN-CENTRAL LA.  AS OUTFLOW BOUNDARY
   ERODES...EFFECTIVE WARM FRONT IS EXPECTED TO BECOME ESTABLISHED MORE
   W-E FROM NERN TX ACROSS SRN AR/NRN LA INTO CENTRAL/SERN MS.  GIVEN
   STEEP LAPSE RATES ALOFT ALREADY IN PLACE AS EVIDENCED BY 12Z
   SOUNDINGS AND AT LEAST MODEST HEATING...AIR MASS SHOULD BECOME
   MODERATELY UNSTABLE OVER MUCH OF THE DEVELOPING WARM SECTOR...WITH
   MARGINAL INSTABILITY REACHING NWWD INTO PORTIONS OF OK/AR.
   
   /EARLY DAY THREATS/
   REFERENCE LATEST SWOMCD AND/OR WATCHES FOR THESE AREAS.
   
   ONGOING...LONG-LIVED LINEAR MCS SHOULD GRADUALLY DIMINISH AS IT
   INGESTS DRIER/MORE STABLE AIR OVER NRN FL/GA.  ALTHOUGH OFFSHORE
   COMPONENT OF THIS LINE MAY REMAIN INTENSE THROUGH THE MORNING ALONG
   THE FL PANHANDLE COAST INTO THE NERN GOM.  AN ISOLATED TORNADO
   AND/OR WIND DAMAGE MAY ACCOMPANY THIS ACTIVITY EARLY TODAY NEAR THE
   COAST.
   
   ELEVATED THUNDERSTORMS ALREADY NEAR SVR LEVELS OVER WRN/CENTRAL OK
   WILL LIKELY INCREASE IN COVERAGE THROUGH THE MORNING/AFTERNOON
   ACROSS MORE OF OK/NRN TX.  ALTHOUGH ACTIVITY WILL BE HIGHLY
   ELEVATED...FORECAST SOUNDINGS SUGGEST STEEP LAPSE RATES...MODEST
   MUCAPE AND SUFFICIENT EFFECTIVE SHEAR WHICH WILL SUPPORT POTENTIAL
   FOR LARGE HAIL.
   
   /MID-LATE DAY THROUGH TONIGHT/
   MODELS ARE IN ALMOST COMPLETE AGREEMENT IN GENERATING THUNDERSTORMS
   AHEAD OF FAST MOVING COLD FRONT OVER ERN TX BETWEEN 18-21Z.  THIS
   ACTIVITY WILL BE SURFACE-BASED AND DEVELOP WITHIN MODERATE MLCAPE
   AND STEEP MID LEVEL LAPSE RATES.  EXPECT THESE STORMS WILL CONTINUE
   TO INCREASE IN BOTH COVERAGE AND INTENSITY ACROSS MUCH OF LA/SRN AR
   THROUGH THE EVENING...OVERSPREADING THE LOWER MS RIVER VALLEY LATE
   THIS EVENING/OVERNIGHT.  DEEP LAYER SHEAR WILL REMAIN QUITE STRONG
   ACROSS THE REGION THROUGHOUT THE PERIOD...DESPITE GENERAL BACKING OF
   MID LEVEL FLOW IN TIME TO A MORE SLY DIRECTION AS DEEP/CLOSED LOW
   PROGRESSES EWD.  MEANWHILE...LOW LEVEL SHEAR SHOULD INTENSIFY LATE
   TODAY/THIS EVENING ALONG AXIS OF STRENGTHENING LLJ.
   
   CONVECTIVE-MODE REMAINS SOMEWHAT UNCERTAIN AS COMPETING INFLUENCES
   OF INTENSE DEEP LAYER SHEAR AND STRONG DOWNSHEAR COMPONENT OF
   STORM-RELATIVE WINDS ALOFT SUGGEST LONGER-LIVED SUPERCELLS...WHILE
   FAST MOTION OF N-S ORIENTED COLD FRONT MAY INHIBIT STORMS FROM
   MOVING OFF INITIATING BOUNDARY.  THIS COULD FORCE A LARGE QLCS WITH
   EMBEDDED LEWPS/SUPERCELLS QUICKLY EWD THROUGH TONIGHT WITH POSSIBLE
   WIDESPREAD WIND DAMAGE AND TORNADOES /SOME OF WHICH COULD BE
   STRONG/.  TORNADO POTENTIAL WILL BE MOST PRONOUNCED INVOF THE
   SURFACE WARM FRONT/LOW CENTER...ALTHOUGH ANY PRECEEDING DEVELOPMENT
   WITHIN BROAD WARM SECTOR WOULD LIKELY REMAIN DISCRETE WITH ATTENDANT
   TORNADO THREAT.  STEEP LAPSE RATES WILL ALSO SUPPORT LARGE HAIL OVER
   A LARGE PART OF THE SRN PLAINS EWD ACROSS THE MID SOUTH/CENTRAL GULF
   COAST STATES THROUGH THE PERIOD...WITH LARGEST HAIL /POSSIBLY
   EXCEEDING 2 INCHES IN DIAMETER/ EXPECTED AS INITIAL SUPERCELLS
   DEVELOP OVER ERN TX/WRN LA IN STRONGEST INSTABILITY THIS
   AFTERNOON/EARLY EVENING.
   
   ..EVANS/GARNER.. 03/27/2009
   
  
   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z