High risk today NE TX & S AR
Posted by JAC on 4/26/2011, 8:51 am


DAY 1 CONVECTIVE OUTLOOK  
  NWS STORM PREDICTION CENTER NORMAN OK
  0734 AM CDT TUE APR 26 2011
 
  VALID 261300Z - 271200Z
 
  ...THERE IS A HIGH RISK OF SVR TSTMS LATE THIS AFTERNOON INTO
  TONIGHT FOR NE TX...FAR SE OK...EXTREME NW LA...AND THE SRN HALF OF
  AR...
 
  ...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK...FROM
  NE TX/SE OK TO THE CONFLUENCE OF THE MS/OH RIVERS...
 
  ...THERE IS A SLGT RISK OF SVR TSTMS IN A BROAD SWATH FROM THE SRN
  PLAINS EWD/NEWD TO THE MS/OH VALLEYS AND THE LOWER GREAT LAKES...
 
  ...DANGEROUS TORNADO AND SEVERE THUNDERSTORM OUTBREAK EXPECTED LATE
  THIS AFTERNOON INTO TONIGHT FROM NE TX ENEWD TO THE MS RIVER...
 
  ...SYNOPSIS...
  AN INITIAL SHORTWAVE TROUGH OVER MO/IL WILL EJECT NEWD TOWARD LOWER
  MI TODAY...WHILE AN INTENSE UPSTREAM JET STREAK PROGRESSES ESEWD TO
  THE SRN PLAINS BY TONIGHT.  MORNING SUBSIDENCE OVER AR /IN THE WAKE
  OF THE DEPARTING WAVE/ WILL BE REPLACED BY ASCENT BEGINNING ALONG
  THE RED RIVER VALLEY OF N TX/SRN OK LATER THIS AFTERNOON...SPREADING
  EWD THIS EVENING INTO SE OK/NE TX AND SRN AR OVERNIGHT.  A STRONG
  SURFACE CYCLONE WILL DEVELOP EWD ALONG THIS SAME CORRIDOR IN
  RESPONSE TO STRONG UPPER DIVERGENCE IN THE LEFT EXIT REGION OF THE
  90-100 KT MIDLEVEL JET.  THE CYCLOGENESIS WILL ALSO PROMOTE THE
  DEVELOPMENT OF A STRENGTHENING SLY/SSWLY LLJ FROM THE ARKLATEX TO
  THE LOWER MS VALLEY OVERNIGHT.  MEANWHILE...RICH BOUNDARY LAYER
  MOISTURE ACROSS E TX...BENEATH A PLUME OF STEEP MIDLEVEL LAPSE RATES
  ORIGINATING TO THE W...WILL PROVIDE MODERATE-STRONG WARM SECTOR
  INSTABILITY IN ADVANCE OF THE DEVELOPING CYCLONE.  THE NET RESULT
  WILL BE A STRONGLY SHEARED AND UNSTABLE WARM SECTOR LATE THIS
  AFTERNOON INTO TONIGHT...WHICH APPEARS SUPPORTIVE OF A DANGEROUS
  TORNADO AND SEVERE THUNDERSTORM OUTBREAK.
 
  ...S/SE AR INTO NW MS TODAY...
  INITIAL WARM ADVECTION STORMS WILL FORM DURING THE DAY ALONG AND N
  OF THE OUTFLOW/WARM FRONT ACROSS S/SE AR AND NW MS...AS LOW-LEVEL
  WAA INCREASES WITH A DEVELOPING LLJ.  A FEW SUPERCELLS ARE EXPECTED
  ALONG THE WARM FRONT...WHERE MODERATE INSTABILITY AND EFFECTIVE SRH
  AOA 200 M2/S2 WILL BE SUPPORTIVE OF A FEW TORNADOES...IN ADDITION TO
  LARGE HAIL AND DAMAGING WINDS.
 
  ...ARKLATEX/SE OK LATE THIS AFTERNOON INTO EARLY TONIGHT...
  OVERNIGHT CONVECTION THAT MOVED OVER AR/NW MS LEFT AN E-W OUTFLOW
  BOUNDARY THAT WILL BECOME THE EFFECTIVE WARM FRONT TODAY.  FARTHER
  S...A WEAKENING MCS OVER SRN LA/MS HAS GENERATED A COLD POOL ACROSS
  CENTRAL LA/E TX...BUT AN UNIMPEDED FEED OF LOW 70S BOUNDARY LAYER
  DEWPOINTS REMAINS TO THE W OF THIS CONVECTION ACROSS SE TX.  THE SE
  TX MOISTURE WILL SURGE NWD TODAY AS THE SRN LA STORMS
  DISSIPATE...WHILE STEEP MIDLEVEL LAPSE RATES WILL CONTINUE TO
  OVERSPREAD THE WARM SECTOR FROM THE W.  THESE PROCESSES...COMBINED
  WITH DAYTIME HEATING...WILL CONTRIBUTE TO AFTERNOON MLCAPE VALUES OF
  2500-3500 J/KG IN THE NE TX WARM SECTOR...WITH SOMEWHAT LESSER
  INSTABILITY FARTHER E ACROSS NRN LA/SRN AR...AND FARTHER N INTO SE
  OK.
 
  SUPERCELLS ARE EXPECTED TO INITIATE BY MID-LATE AFTERNOON ACROSS
  N/NE TX...ALONG THE WARM FRONT AND DRYLINE TO THE IMMEDIATE E/SE OF
  THE SURFACE LOW...AND SPREAD EWD TOWARD SW AR/NW LA THROUGH TONIGHT.
  THE STRONG INSTABILITY...EFFECTIVE BULK SHEAR IN EXCESS OF 60
  KT...EFFECTIVE SRH OF 300-500 M2/S2...AND A SUFFICIENTLY MOIST
  BOUNDARY LAYER WILL BE FAVORABLE FOR LONG-TRACK/DAMAGING TORNADOES
  WITH DISCRETE AND CLUSTER SUPERCELLS INTO THE LATE EVENING/EARLY
  NIGHTTIME HOURS.  VERY LARGE HAIL AND DAMAGING WINDS WILL ALSO BE
  LIKELY WITH THE INITIAL SUPERCELLS.
 
  ...NRN LA/SE AR/NW MS/WRN TN TONIGHT...
  AS THE STRONG SYNOPTIC CYCLONE PROGRESSES EWD AND INTERACTS WITH THE
  UNSTABLE WARM SECTOR...INTENSE CONVECTION IS LIKELY THROUGH THE
  OVERNIGHT HOURS.  INITIAL TORNADIC SUPERCELLS IN NE TX/SW AR AREA
  SHOULD EVENTUALLY GROW UPSCALE INTO ONE OR MORE INTENSE
  MCS/S...WHICH COULD EVOLVE INTO BOW ECHOES WITH THE POTENTIAL FOR
  WIDESPREAD/INTENSE DAMAGING WINDS...AS WELL AS TORNADOES.  THIS
  ACTIVITY SHOULD PROGRESS QUICKLY EWD/NEWD TO THE MS RIVER LATE
  TONIGHT AS THE SYNOPTIC WAVE BEGINS TO EJECT ENEWD.
 
  ...OH VALLEY REGION THROUGH EARLY TONIGHT...
  THE EJECTING LEAD SHORTWAVE TROUGH WILL PROVIDE A BROAD SWATH OF
  MODERATE-STRONG SWLY MIDLEVEL FLOW...ABOVE RESIDUAL BOUNDARY LAYER
  DEWPOINTS IN THE UPPER 50S TO LOWER 60S.  THE LINGERING CLOUDS AND
  RESIDUAL OUTFLOW FROM PRIOR CONVECTION MAKE THE CONVECTIVE EVOLUTION
  SOMEWHAT UNCERTAIN TODAY ACROSS THE OH VALLEY REGION...THOUGH
  SURFACE-BASED INSTABILITY WILL BE SUFFICIENT FOR A FEW SUPERCELLS
  AND/OR BOWING SEGMENTS WITH A RISK FOR A COUPLE OF
  TORNADOES...DAMAGING WINDS...AND ISOLATED LARGE HAIL.
 
  ..THOMPSON/COHEN.. 04/26/2011
 
50
In this thread:
Potential for Big Outbreak Wednesday TN, KY, N AL & N GA - JAC, 4/26/2011, 6:48 am
< Return to the front page of the: message board | monthly archive this page is in
Post A Reply
This thread has been archived and can no longer receive replies.