[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 201258
SWODY1
SPC AC 201256

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0656 AM CST MON MAR 20 2006

VALID 201300Z - 211200Z

...THERE IS A MDT RISK OF SVR TSTMS TODAY ACROSS CENTRAL MS AND
EXTREME W CENTRAL AL....

...THERE IS A SLGT RISK OF SVR TSTMS TODAY INTO EARLY TONIGHT FROM
OK ACROSS THE LOWER MS VALLEY TO WRN GA....

...SYNOPSIS...
COMPLEX SITUATION TODAY ACROSS THE SRN PLAINS AND LOWER MS VALLEY
WITH MULTIPLE CLUSTERS OF ONGOING CONVECTION IN ADVANCE OF THE DEEP
MID LEVEL TROUGH THAT IS BEGINNING TO EJECT ENEWD OVER THE SRN HIGH
PLAINS.  AN INITIAL BAND OF CONVECTION FROM SE AR INTO SE TX HAS
PRODUCED A SUBSTANTIAL COLD POOL THAT HAS REINFORCED THE COOL/STABLE
AIR MASS ACROSS E TX AND NW LA.  SHORT TERM MODEL FORECASTS
/ESPECIALLY THE 00Z AND 06Z NAM/ DO NOT REFLECT THE IMPACTS OF THIS
CONVECTION PARTICULARLY WELL...WHICH AFFECTS THE TRACK OF THE
INITIAL SURFACE LOW ACROSS THE LOWER MS VALLEY...AS WELL AS THE
DEGREE OF INSTABILITY LATER TODAY ACROSS NRN LA/NE TX/AR.

...CENTRAL LA/MS AREA TODAY...
WELL IN ADVANCE OF THE DEEP MID LEVEL TROUGH OVER THE SRN HIGH
PLAINS...A CONVECTIVELY INDUCED VORT MAX OVER SE TX WILL MOVE ENEWD
ACROSS CENTRAL LA THIS MORNING...AND CENTRAL MS THIS AFTERNOON IF IT
SURVIVES.  OUTFLOW FROM OVERNIGHT STORMS WILL TEND TO LIMIT THE NWD
RETURN OF THE WARM FRONT ACROSS LA/MS THE FIRST HALF OF THE
DAY...WITH THE HIGHEST CONFIDENCE IN ESTABLISHING THE SURFACE WARM
SECTOR NEAR AND S OF I-20 BY AFTERNOON.  BOUNDARY LAYER DEWPOINTS IN
THE MID-UPPER 60S AND TEMPERATURES IN THE 70S WILL SUPPORT MODERATE
INSTABILITY IN THE WARM SECTOR /MLCAPE OF 1000-1500 J/KG/. 
ADDITIONALLY...VERTICAL SHEAR WILL BE FAVORABLE FOR SUPERCELLS INVOF
THE SURFACE WARM FRONT...WHERE RICH L0W-LEVEL MOISTURE AND ENHANCED
LOW-LEVEL SHEAR SHOULD PROVIDE A FOCUS FOR THE TORNADO THREAT TODAY.
 THE SEVERE THREAT SHOULD PEAK THIS AFTERNOON...AND THEN GRADUALLY
DIMINISH ACROSS AL BY EARLY TONIGHT.

...OK AREA THIS AFTERNOON/EARLY EVENING...
THE MID LEVEL COLD CORE LOW OVER ERN NM WILL ROTATE EWD TO WRN OK BY
MID-LATE AFTERNOON.  STEEP L0W-MID LEVEL LAPSE RATES AND 500 MB
TEMPERATURES NEAR -25 C WILL SUPPORT SURFACE-BASED INSTABILITY
DESPITE RESIDUAL BOUNDARY LAYER DEWPOINTS IN THE 40S AND
TEMPERATURES MAINLY IN THE 50S.  GIVEN THE COLD MID LEVEL
TEMPERATURES AND MODEST VERTICAL SHEAR ON THE CYCLONIC SIDE OF THE
MID-UPPER JET...LOW-TOPPED SUPERCELLS WITH MARGINALLY SEVERE HAIL
CAN BE EXPECTED THIS AFTERNOON NEAR THE TRACK OF THE OCCLUDED
SURFACE LOW. 

...ARKLATEX REGION TODAY INTO EARLY TONIGHT...
SUBSTANTIAL UNCERTAINTY EXISTS REGARDING THE DEGREE OF
DESTABILIZATION IN THE WAKE OF OVERNIGHT AND MORNING CONVECTION. 
PRESENT INDICATIONS ARE THAT WHAT DESTABILIZATION OCCURS ACROSS NE
TX/SE OK/SW AR WILL LIKELY BE ABOVE THE SURFACE...ORIGINATING FROM
THE STEEP LAPSE RATE PLUME OVER S TX.  THE STRONGER STORMS THIS AREA
COULD PRODUCE MARGINALLY SEVERE HAIL THROUGH EARLY TONIGHT...THOUGH
SEVERE STORM COVERAGE SHOULD REMAIN ISOLATED AT BEST.

..THOMPSON/GUYER.. 03/20/2006