Line of fire Monday
Posted by JAC on 4/3/2011, 8:17 am



DAY 2 CONVECTIVE OUTLOOK  
  NWS STORM PREDICTION CENTER NORMAN OK
  1256 AM CDT SUN APR 03 2011
 
  VALID 041200Z - 051200Z
 
  ...THERE IS A SLGT RISK OF SVR TSTMS EXTENDING FROM E TX TO CENTRAL
  GULF COAST STATES AND NWD TO THE OH VALLEY...
 
  ...SYNOPSIS...
  THE 02/12Z ECMWF IS CONSISTENT WITH ITS 02/00Z RUN...AND REMAINS THE
  SLOWEST AND FARTHEST SOUTH OF THE OPERATIONAL AND LATEST 21Z SREF
  500 MB MEAN HEIGHTS...SHOWING THE BASAL SHORTWAVE TROUGH MOVING INTO
  THE LOWER MS VALLEY DURING THE LATTER HALF OF DAY 2.  HOWEVER...EVEN
  WITH THE SLOWER ECMWF SOLUTION...60-100 METER HEIGHT FALLS ARE
  EXPECTED IN ADVANCE OF THE PROGRESSIVE FULL LATITUDE TROUGH FROM THE
  OH VALLEY TO MID SOUTH/LOWER MS VALLEY SUPPORTING STRONG DEEP LAYER
  SSWLY WIND FIELDS.  THE 03/00Z GFS COMPARED TO THIS MODEL RUN FROM
  02/00Z IS NOW INDICATING STRONGER FORCING FOR ASCENT INTO THE MID
  SOUTH BY MONDAY AFTERNOON.
 
  IN THE LOW LEVELS...THE LATEST GFS CONTINUES TO INDICATE STRONGER
  DEEPENING OF THE SURFACE LOW...WITH BOTH THE 00Z GFS/12Z ECMWF
  TRACKING THE LOW FROM THE CENTRAL GREAT LAKES TO QUEBEC.  EACH MODEL
  CONTINUES TO SHOW STRONG BAROCLINICITY AS A COLD FRONT ADVANCES EWD
  ACROSS THE OH/TN AND LOWER MS VALLEYS AND CENTRAL GULF COAST STATES.
   THE ECMWF REMAINS THE SLOWER MODEL WITH EWD PROGRESSION OF THE COLD
  FRONT...AND IN AGREEMENT WITH HPC MODEL DIAGNOSTICS HAVE KEPT SERN
  EXTENT OF THE SLIGHT RISK IN LINE WITH THE ECMWF TIMING OF THE COLD
  FRONT INTO GA BY 12Z TUESDAY.
 
  ...E TX TO CENTRAL GULF COAST STATES NWD TO TN/OH VALLEYS...
  GREATEST SEVERE WEATHER THREAT AREA /COVERAGE AND INTENSITY/...
  INCLUDING POTENTIAL FOR TORNADOES...DAMAGING WINDS AND HAIL IS
  EXPECTED TO BE ACROSS THE LOWER MS/TN VALLEYS.
 
  DESPITE THE MODEL DIFFERENCES DISCUSSED IN THE SYNOPSIS...EVEN 60-90
  METER HEIGHT FALLS PER ECMWF FROM THE OH VALLEY TO THE MID
  SOUTH/LOWER MS VALLEY AND MID-UPPER LEVEL TROUGH BECOMING NEUTRALLY
  ORIENTED WILL SUPPORT FORCING FOR ASCENT SPREADING EWD ATOP THE COLD
  FRONT AND ADJACENT WARM SECTOR.  STEEP MIDLEVEL LAPSE RATES /8-9 C
  PER KM/ ACROSS THE SLIGHT RISK AREA AT 12Z MONDAY WILL INITIALLY CAP
  THE AIR MASS.  HOWEVER...THE HEIGHT FALLS ARE EXPECTED TO ELIMINATE
  THE CAP EARLY IN THE PERIOD /MONDAY MORNING/.  FORCING ATTENDANT TO
  THE TROUGH SHOULD MAINTAIN ONGOING TSTMS ALONG THE FRONT WHICH WILL
  EXTEND FROM LOWER MI SWWD TO NERN AND CENTRAL TX...WHILE NEW STORMS
  WILL ALSO DEVELOP AS THE CAP WEAKENS FROM W-E MONDAY MORNING INTO
  THE AFTERNOON.
 
  SLY LOW LEVEL WINDS WILL SPREAD MOISTURE NWD IN ADVANCE OF THE COLD
  FRONT...WITH SURFACE DEWPOINTS IN THE LOWER 60S SPREADING ACROSS THE
  OH VALLEY...AND MID-UPPER 60S SWD FROM TN.  VALUES AROUND 70 SHOULD
  BE ALONG THE GULF COAST.  THIS MOISTURE COMBINED WITH RELATIVELY
  STEEP MIDLEVEL LAPSE RATES SHOULD RESULT IN MODERATE INSTABILITY
  FROM E TX TO CENTRAL GULF COAST STATES AND INTO PARTS OF THE TN
  VALLEY.  INCREASING DEEP LAYER SHEAR VECTORS BECOMING LESS PARALLEL
  TO THE COLD FRONT ACROSS THIS REGION SUGGESTS SUPERCELLS WILL BE
  MORE LIKELY.  GIVEN THE STRENGTH OF THE LOW LEVEL SHEAR...TORNADOES
  WILL BE POSSIBLE IN ADDITION TO DAMAGING WINDS AND HAIL /SOME VERY
  LARGE/.  SEVERE WEATHER THREAT SHOULD PERSIST ACROSS THE CENTRAL
  GULF COAST STATES MONDAY NIGHT AS THE COLD FRONT SPREADS EWD INTO A
  MODERATELY UNSTABLE AND STRONGLY SHEARED ENVIRONMENT.
 
  FARTHER N INTO THE OH VALLEY INSTABILITY WILL BE WEAKER.  HOWEVER...
  FORCING FOR ASCENT WITH THE UPPER TROUGH AND POSSIBLY ASSOCIATED
  WITH A LEAD IMPULSE WILL SUPPORT TSTM DEVELOPMENT AS THE COLD FRONT
  ADVANCES EWD.  BULK SHEAR VECTORS ORIENTED MORE PARALLEL TO THE
  FRONT SUGGEST A LINEAR MODE WITH THE STRENGTH OF LOW LEVEL WINDS
  /50-60 KT/ SUGGEST DAMAGING WINDS WILL BE THE PRIMARY THREAT.
 
  ..PETERS.. 04/03/2011
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Sunday: possible severe outbreak. Strong tornadoes OK & N TX - JAC, 4/2/2011, 8:47 am
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