[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 201251
SWODY1
SPC AC 201250

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT THU APR 20 2006

VALID 201300Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM WRN AND SRN TX NE THROUGH
THE ARKLATEX INTO THE TN VLY...

...SYNOPSIS...
DEEP CLOSED LOW OVER THE UPR MS VLY WILL EDGE ONLY SLOWLY E THIS
PERIOD AND WILL DOMINATE THE FLOW FIELD ACROSS MUCH OF THE U.S. 
FARTHER S...SHORTWAVE TROUGH NOW ALONG THE AZ/NM BORDER EXPECTED TO
CONTINUE E AT A SOMEWHAT GREATER CLIP...REACHING E TX/SE OK BY 12Z
SATURDAY.  DOWNSTREAM FROM THE AZ/NM SYSTEM...A WEAKER
CONVECTIVELY-ENHANCED DISTURBANCE NOW APPARENT IN SATELLITE AND
RADAR DATA OVER THE ARKLATEX REGION SHOULD CONTINUE ENE INTO THE TN
VLY LATER TODAY...BEFORE TURNING MORE NE TOWARD THE CNTRL
APPALACHIANS TONIGHT.

THE TWO SRN SHORTWAVES WILL ENHANCE ASCENT ALONG QUASI-STATIONARY
FRONT FROM S TX INTO THE TN VLY AND...ALONG WITH DIURNAL HEATING
...WILL BE THE PRIME FACTORS MODULATING CONVECTIVE DEVELOPMENT THIS
PERIOD.

...SW TX TO THE ARKLATEX...
VERY MOIST AIR /DEWPOINTS IN THE MID 60S TO LOWER 70S/ IS IN PLACE
ALONG AND S OF STALLED FRONTAL ZONE ORIENTED ROUGHLY NEWD FROM S
CNTRL TX.  CLOUD DEBRIS FROM OVERNIGHT STORMS AND ADDITIONAL STRATUS
DEVELOPMENT LIKELY WILL LIMIT SURFACE HEATING IN WARM SECTOR TO SOME
EXTENT.  BUT FAIRLY SUBSTANTIAL SURFACE-BASED DESTABILIZATION
/MLCAPE TO 2000 J PER KG/ SHOULD NEVERTHELESS OCCUR FROM THE BIG
BEND REGION ENE ALONG FRONT INTO CNTRL TX.

INCREASING LARGE SCALE ASCENT ASSOCIATED WITH APPROACHING AZ/NM
TROUGH...ALREADY RESPONSIBLE FOR RECENT DEVELOPMENT OF ELEVATED
STORMS IN W CNTRL TX...SHOULD FURTHER ENHANCE DESTABILIZATION AND
SUPPORT SCATTERED AREAS OF STORM DEVELOPMENT BY MID AFTERNOON. 40
KT WSWLY MID LEVEL FLOW DOWNSTREAM FROM TROUGH WILL CONTRIBUTE
SUFFICIENT SHEAR FOR SUPERCELLS WITH VERY LARGE HAIL.  POTENTIAL
WILL ALSO EXIST FOR A FEW STORMS TO MOVE ALONG FRONT AND/OR OUTFLOW
BOUNDARY SEGMENTS THAT SHOULD BE FAVORABLY ORIENTED TO ENHANCE LOW
LEVEL SRH/TORNADO DEVELOPMENT. COMBINATION OF INCREASING
INSTABILITY CONCURRENT WITH DIURNAL HEATING...AND PRESENCE OF
FRONT/OUTFLOW BOUNDARIES...SUGGEST THAT SOME OF THE STORMS WILL
FAIRLY QUICKLY ORGANIZE INTO BANDS AND/OR CLUSTERS.  THESE SYSTEMS
SHOULD MOVE/DEVELOP GENERALLY E TOWARD THE TX CSTL PLN LATER
TODAY/TONIGHT...WHERE THERE WILL EXIST A THREAT FOR BOWING SEGMENTS
WITH HIGH WIND/HAIL AND PERHAPS A COUPLE  TORNADOES.

FARTHER N...EXPECT INCREASING COVERAGE OF SLIGHTLY ELEVATED STORMS
WITH HAIL AND POSSIBLY DAMAGING WIND FROM W CNTRL TX ENE THROUGH THE
ARKLATEX LATER TODAY/TONIGHT AS WARM/MOISTURE ADVECTION STRENGTHEN
AHEAD OF PROGRESSIVE AZ/NM TROUGH.

...LWR MS/TN VLY TO SRN/CNTRL APLCNS...
POCKET OF STRONG SURFACE-BASED INSTABILITY /SBCAPE TO 2500 J PER KG/
LIKELY WILL DEVELOP OVER NRN MS/SRN MIDDLE TN AND NRN/CNTRL AL WITH
HEATING TODAY. THIS REGION WILL BE GLANCED BY ENHANCED WSWLY FLOW
ASSOCIATED WITH ARKLATEX MCV.  WHILE LOW LEVEL WIND FIELD LIKELY
WILL REMAIN WEAK...COMBINATION OF STEEP LOW TO MID LEVEL LAPSE RATES
AND 40-50 KT WSWLY MID LEVEL FLOW /PER SHV 12Z RAOB/ MAY PROVE
FAVORABLE FOR CLUSTERS OF STORMS/POSSIBLE SUPERCELLS WITH VERY LARGE
HAIL AND POSSIBLY HIGH WIND.  THIS ACTIVITY SHOULD DEVELOP ACROSS
NRN MS/SRN MIDDLE TN BY MID TO LATE MORNING...AND MAY TEND TO SPREAD
MORE W TO E THAN WAS THE CASE YESTERDAY AS UPPER FLOW HAS BACKED
CONSIDERABLY RELATIVE TO WEDNESDAY.  

FARTHER N...MORE WIDELY SCATTERED PULSE STORMS WITH MARGINALLY
SEVERE HAIL MAY OCCUR EPISODICALLY NWD INTO PARTS OF KY
AND...ESPECIALLY LATER IN THE PERIOD...NEWD INTO THE CNTRL
APPALACHIANS.

..CORFIDI/JEWELL.. 04/20/2006