Possible Significant Tornado Risk along MS River this Evening
Posted by JAC on 4/23/2010, 7:38 am
RUC showing Cap will be in place most of the day with a high CAPE in feed.

Need to watch if the cap breaks.  If so, could see some heavy-duty cells pop up quickly.

Helicity looks good for torando formation with a strong jet on its tail.

Stay tuned.











DAY 1 CONVECTIVE OUTLOOK  
  NWS STORM PREDICTION CENTER NORMAN OK
  1258 AM CDT FRI APR 23 2010
 
  VALID 231200Z - 241200Z
 
  ...THERE IS A MDT RISK OF SVR TSTMS PORTIONS AR...WRN
  MS...CENTRAL/NRN LA...ERN TX...EXTREME SERN OK...
 
  ...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM NEB TO CENTRAL
  IL...THEN SWD TO S-CENTRAL/SE TX...LA GULF COAST AND WRN AL...
 
  ...SYNOPSIS...
  IN MID-UPPER LEVELS...SPLIT-FLOW PATTERN PREDOMINATES ACROSS
  WRN/CENTRAL NORTH AMERICA...FEATURING LARGE CYCLONIC GYRE CENTERED
  OVER AZ AND COVERING AREA FROM WY-BAJA AND SRN CA TO CENTRAL HIGH
  PLAINS.  LEADING SHORTWAVE TROUGH -- LOCATED OVER SWRN NM AS OF
  23/04Z...IS FCST TO LIFT NEWD TO ERN CO BY BEGINNING OF PERIOD AND
  BECOME PRIMARY LOW WITHIN BROADER CYCLONIC VORTEX ALOFT.  THIS LOW
  THEN SHOULD MOVE EWD ACROSS CENTRAL PLAINS...WITH RELATED 500 MB
  CYCLONE COVERING MOST OF KS/NEB.  MEANWHILE...TRAILING SHORTWAVE AND
  SPEED MAX OVER SRN CA SHOULD PIVOT SEWD THEN EWD ACROSS NERN
  MEX...NM/MEX BORDERLANDS...TO W-CENTRAL TX BY 24/12Z.  INITIAL/NET
  POSITIVE TILTING TO CENTRAL CONUS TROUGHING WILL BECOME NEARLY
  NEUTRAL BY END OF PERIOD.
 
  AT SFC...CYCLONE INITIALLY OVER SERN CO IS EXPECTED TO MIGRATE
  SLOWLY NEWD ACROSS WRN/NRN KS THROUGH PERIOD...OCCLUDING WHILE
  COLD/WARM FRONTAL TRIPLE POINT MOVES AWAY TO ITS NE OVER SERN NEB.
  COLD FRONT SHOULD MOVE SEWD ACROSS MOST OF TX/OK.  MOST
  DETERMINISTIC AND ENSEMBLE PROGS INDICATE TEMPORARY STALLING OR WEAK
  WAVE DEVELOPMENT ALONG FRONT OVERNIGHT OVER E TX...KEEPING SOME
  PARTS OF E TX IN WARM SECTOR UNTIL END OF PERIOD.  WARM FRONT NOW
  OVER SRN/CENTRAL KS WILL MOVE NEWD...PERHAPS RE-FORMING BY MIDDAY
  LOCAL TIME FROM SERN NEB ACROSS ERN KS TO OZARKS...THEN CROSSING
  PORTIONS WRN/CENTRAL IA AND CENTRAL IL BY END OF PERIOD.
 
  ...S-CENTRAL/ERN TX AND ARKLATEX REGION TO LOWER MS VALLEY...
  CONFIDENCE IS INCREASING IN POTENTIAL FOR MULTIPLE TORNADOES  OVER
  CATEGORICAL MDT-RISK AREA...SOME POSSIBLY STG-VIOLENT.  ATTM MOST
  PROBABLE SCENARIO IS FOR AT LEAST TWO TEMPORALLY SEPARATED SVR
  EPISODES WITH SOME SPATIAL OVERLAP...
  1. AFTERNOON/EVENING FROM S-CENTRAL/ERN TX THROUGH ARKLATEX
  REGION...AND
  2. OVERNIGHT AND CONTINUING INTO DAY-2 PERIOD...ESPECIALLY OVER
  PORTIONS LA/MS.
  ONE OR TWO CORRIDORS OF RELATIVELY CONCENTRATED/STRONG-VIOLENT
  TORNADO THREAT MAY DEVELOP WITHIN BROADER OUTLOOK AREAS NOW
  DELINEATED.  CONCERNS ABOUT COVERAGE/DURATION OF FAVORABLE SUPERCELL
  MODES PRECLUDES GREATER CATEGORICAL OUTLOOK THIS SOON.
 
  AHEAD OF COLD FRONT...LOW-LEVEL MOISTURE FCST TO INCREASE THROUGHOUT
  MOST OF PERIOD ACROSS LOWER MS VALLEY REGION.  THIS WILL LEAD TO
  BROADENING OF FAVORABLE WARM SECTOR FOR SFC-BASED EFFECTIVE
  PARCELS...BENEATH STRENGTHENING DEEP-LAYER WIND PROFILES QUITE
  FAVORABLE FOR DISCRETE SUPERCELLS TO PRODUCE TORNADOES.  FORECAST
  SHEAR/MOISTURE/BUOYANCY COMBINATION OVERNIGHT...IN PARTICULAR...IS
  AN ESPECIALLY PRONOUNCED MOISTURE SURGE IS REASONABLY EVIDENT IN
  PROGS AFTER 00Z AS SECOND SHORTWAVE TROUGH APCHS...FRONTAL-WAVE LOW
  FORMS...AND LOW-LEVEL FLOW BACKS IN RESPONSE TO RELATED
  HEIGHT/PRESSURE FALLS.  850 MB WINDS ARE PROGGED TO BACK AND
  STRENGTHEN MARKEDLY ACROSS LA BETWEEN 24/06Z-24/12Z...LENGTHENING
  HODOGRAPHS ENOUGH TO JUXTAPOSE 300-400 J/KG OF 0-1 KM SRH WITH
  1500-2000 J/KG MLCAPE AND NEARLY 60 KT EFFECTIVE SHEAR
  MAGNITUDE...ALL IN LAST FEW HOURS OF PERIOD.
 
  SEPARATE AREA OF SCATTERED TSTMS ALSO MAY DEVELOP THIS AFTERNOON
  ACROSS PORTIONS CENTRAL/SRN LA AND SWRN MS...WITH POTENTIAL FOR SOME
  TORNADIC SUPERCELLS AS WELL.  AIR MASS WILL BE CHARACTERIZED BY
  ENOUGH CINH THAT TSTMS MAY REMAIN DISCRETE...WITH LARGE LOW-LEVEL
  HODOGRAPHS NEAR LEADING/NERN EDGE OF DEEP/MOIST BOUNDARY LAYER
  CHARACTERIZING RETURN FLOW REGIME.  MLCAPE 2000-2500 J/KG AND 0-1 KM
  SRH OVER 300 J/KG ARE POSSIBLE IN THAT TRANSITION ZONE.
 
  ...CENTRAL PLAINS...LOWER MO VALLEY REGION...
  SCATTERED-NUMEROUS TSTMS ARE EXPECTED IN NEAR-FRONTAL ARC
  ACCOMPANYING NRN SEMICIRCLE OF OCCLUDED LOW-LEVEL CYCLONE.
  CORRESPONDING CORRIDOR OF SFC-BASED DESTABILIZATION IS EXPECTED TO
  ARC ACROSS CENTRAL/SRN NEB TO NWRN MO...AND POSSIBLY AS FAR WSW AS
  EXTREME NERN CO.  STEEP MIDLEVEL LAPSE RATES WILL SUPPORT MLCAPE
  POTENTIALLY REACHING NEAR 1500 J/KG...WITH AROUND 50 KT EFFECTIVE
  SHEAR AND 0-1 KM SRH 150-300 J/KG IN SEVERAL MODIFIED FCST
  SOUNDINGS.  ABUNDANT LOW-LEVEL VORTICITY AND NARROW RIBBON OF
  ENHANCED SRH WILL SUPPORT POTENTIAL FOR SUPERCELLS...LARGE/DAMAGING
  HAIL...OCCASIONAL DAMAGING GUSTS...AND AT LEAST A FEW TORNADOES.
  THREAT SHOULD WANE CONSIDERABLY AFTER DARK AS SUPPORTIVE LOW-LEVEL
  INSTABILITY DECREASES...DUE TO COMBINATION OF CONVECTIVE OUTFLOW AND
  DIABATIC SFC COOLING.
 
  ..EDWARDS/GARNER.. 04/23/2010
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Setting up for some weather this weekend......... - Tiny, 4/22/2010, 12:02 pm
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