[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 190607
SWODY1
SPC AC 190605

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0105 AM CDT WED APR 19 2006

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE TX HILL
COUNTRY/EDWARDS PLATEAU EWD TO THE UPPER TN VALLEY/SERN STATES...

...SYNOPSIS...
LARGE CUT-OFF MID/UPPER LEVEL LOW INITIALLY LOCATED OVER THE NRN
PLAINS WILL WEAKEN SLIGHTLY TODAY AS OMEGA BLOCK SHIFTS SLIGHTLY
EWD.  BY THE END OF THE PERIOD...MODELS CONTINUE TO INDICATE LARGE
SCALE PATTERN EVOLVING INTO MORE OF A REX BLOCK FROM THE NRN
PLAINS/UPPER MS VALLEY CLOSED LOW NNEWD INTO HUDSON BAY REGION. 
MEANWHILE...WATER VAPOR IMAGERY INDICATED A SERIES OF MAINLY WEAK
MID-LEVEL IMPULSES TRAVERSING SRN STREAM FLOW FROM SRN BAJA/NRN
MEXICO ENEWD TO THE LOWER MS VALLEY...AND THEN TURNING E/SELY ACROSS
MS/AL INTO SERN STATES.  FARTHER W...A SHORT WAVE TROUGH CURRENTLY
MOVING INTO SRN CA WILL MOVE EWD REACHING AZ/NM BY 12Z THURSDAY.

IN THE LOW-LEVELS...SURFACE LOW IS EXPECTED SLOWLY FILL AS IT MOVES
EWD ACROSS KY THIS FORECAST PERIOD.  COLD FRONTAL SURGE IS EXPECTED
TO SLOW TODAY AS THIS BOUNDARY BECOMES ORIENTED PARALLEL TO THE SRN
BRANCH OF THE WESTERLIES.

...OH/TN VALLEYS INTO THE SERN STATES...
CLUSTER OF THUNDERSTORMS/MCS IS EXPECTED TO BE ONGOING AT START OF
PERIOD ACROSS PARTS OF LOWER OH/UPPER TN VALLEYS AND SRN
APPALACHIANS.  WAA REGIME PER WLY LLJ VEERING TO WNWLY ACROSS THE
SERN STATES IS EXPECTED TO SUPPORT DOWNSTREAM DESTABILIZATION TO
MAINTAIN THIS ACTIVITY ACROSS WRN NC/SC/GA THIS MORNING AND
AFTERNOON...WITH ATTENDANT THREATS OF DAMAGING WINDS AND HAIL.
POTENTIAL OUTFLOW BOUNDARY FROM THIS COMPLEX AND/OR ZONE OF
DIFFERENTIAL HEATING EXPECTED ACROSS GA ALONG WRN PERIPHERY OF CLOUD
SHIELD SHOULD RE-ENFORCE RESIDUAL BOUNDARY DRAPED SEWD ACROSS THIS
AREA INTO FL.

SURFACE HEATING EXPECTED IN THE WAKE OF THIS INITIAL ACTIVITY
COMBINED WITH SURFACE DEWPOINTS IN THE MID 60S AND STEEP MID-LEVEL
LAPSE RATES SHOULD RESULT IN MUCAPES OF 2000-3000 J/KG EXTENDING
FROM THE SURFACE LOW INTO ERN AL/GA.  LARGE SCALE ASCENT WITH A
MID-LEVEL IMPULSE...CURRENTLY MOVING THROUGH THE ARKLATEX
REGION...IS EXPECTED TO TRANSLATE SEWD ACROSS ERN GULF COAST STATES
AIDING IN THUNDERSTORM DEVELOPMENT ALONG THE SE-NW ORIENTED SURFACE
BOUNDARY THIS AFTERNOON.  STRONG DEEP LAYER SHEAR WILL SUPPORT
ORGANIZED STORMS/SUPERCELLS WITH ATTENDANT THREAT OF HAIL/ DAMAGING
WINDS AND PERHAPS A COUPLE OF TORNADOES.

...TX HILL COUNTRY/EDWARDS PLATEAU TO NERN TX/LOWER MS VALLEY...
40 KT OF SWLY MID-LEVEL FLOW IS EXPECTED TO EXTEND FROM SWRN TX AND
THE TX HILL COUNTRY TO AR/LOWER TN VALLEY.  BY EARLY
AFTERNOON...COLD FRONT SHOULD EXTEND FROM MIDDLE TN/NRN MS WSWWD
INTO NERN TX AND THEN TO THE RIO GRANDE VALLEY NEAR DRT.  MODERATE
INSTABILITY IS EXPECTED ALONG/S OF THIS BOUNDARY...GIVEN STRONG
SURFACE HEATING WITHIN A MOIST AIR MASS AND BENEATH STEEP MID-LEVEL
LAPSE RATES.

MUCH OF THE STRONGER FLOW ALOFT IS PROGGED TO BE OVER THE
POST-FRONTAL AIR MASS RESULTING IN RATHER WEAK DEEP LAYER SHEAR
ACROSS PARTS OF THE LOWER MS VALLEY THIS AFTERNOON...LIMITING STORM
ORGANIZATION.  AN EXCEPTION SHOULD BE FARTHER SW ACROSS THE TX HILL
COUNTRY WHERE THE STRONG FLOW ALOFT WILL SUPPORT FAVORABLE DEEP
LAYER SHEAR FOR ORGANIZED STORMS.  ANY STORMS THAT DEVELOP OVER THIS
REGION WILL BE CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WINDS.

THUNDERSTORM COVERAGE IS EXPECTED TO INCREASE N/NEWD FROM THE TX
HILL COUNTRY INTO PARTS OF CENTRAL TO NERN TX AND PERHAPS INTO SRN
AR/NRN LA AS ISENTROPIC ASCENT INCREASES N OF SURFACE BOUNDARY LATER
THIS EVENING/TONIGHT.  STRENGTHENING SWLY MID-LEVEL WINDS AHEAD OF
SWRN STATES SHORT WAVE TROUGH ARE EXPECTED TO RESULT IN SUFFICIENT
EFFECTIVE DEEP LAYER SHEAR FOR SOME STORM ORGANIZATION GIVEN
MODERATE INSTABILITY.  HAIL WOULD BE THE PRIMARY THREAT WITH THE
OVERNIGHT ACTIVITY.

..PETERS/JEWELL.. 04/19/2006