[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 180521
SWODY2
SPC AC 180520

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1220 AM CDT TUE APR 18 2006

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE SRN OH AND TN
VALLEYS INTO AL AND GA...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE TX HILL
COUNTRY AND EDWARDS PLATEAU...

...SYNOPSIS...

OMEGA BLOCK FROM THE NRN PLAINS INTO THE WRN ATLANTIC WILL GRADUALLY
SHIFT EWD THROUGH THE DAY TWO PERIOD WITH MORE OF A REX BLOCK
PATTERN BECOMING BETTER DEFINED FROM THE NRN PLAINS/UPPER MS VALLEY
INTO HUDSON BAY.  A SLIGHTLY MORE PROGRESSIVE SRN BRANCH OF
WESTERLIES WILL PERSIST FROM THE SWRN DESERTS EWD THROUGH THE GULF
COAST STATES WITH A VORTICITY MAXIMUM TRANSLATING FROM THE SRN CA
COAST EWD INTO AZ.

IN THE LOW-LEVELS...LOW PRESSURE OVER WRN TN WILL SLOWLY DEVELOP EWD
THROUGH THE TN VALLEY BEFORE WEAKENING WITH COLD FRONTAL SURGE ALSO
SLOWING OVER THE TN VALLEY SWWD THROUGH THE LOWER MS VALLEY INTO
CNTRL TX.  MEANWHILE...WEAK BACK DOOR FRONT INITIALLY FROM ERN KY/TN
SEWD TO OFF THE NERN FL COAST WILL SLOWLY RETREAT EWD THROUGH THE
PERIOD.

...OH AND TN VALLEYS INTO THE SERN STATES...

CLUSTERS OF TSTMS ARE EXPECTED TO BE ONGOING AT THE ONSET OF THE
FORECAST PERIOD OVER THE TN AND SRN OH VALLEYS WEDNESDAY MORNING
DRIVEN LARGELY BY WAA ALONG WSWLY LLJ AXIS.  THIS ACTIVITY WILL
LIKELY CONTINUE EWD OR SEWD WEDNESDAY WITH SOME THREAT OF MARGINALLY
SEVERE HAIL INTO THE CNTRL/SRN APPALACHIANS.  A MODERATELY UNSTABLE
AIR MASS /MLCAPES OF 1000-2000 J/KG/ IS EXPECTED TO DEVELOP BY
AFTERNOON IN THE WAKE OF THIS ACTIVITY AHEAD OF COLD FRONT OWING TO
MOIST BOUNDARY-LAYER CONDITIONS AND DIABATIC HEATING.

WHILE LARGE-SCALE FORCING IS FORECAST TO REMAIN LARGELY NEUTRAL
ACROSS REGION...A RELATIVELY WEAK CAP AND SUSTAINED FRONTAL
CONVERGENCE SHOULD BE SUFFICIENT TO INITIATE MORE VIGOROUS
SURFACE-BASED DEVELOPMENT BY AFTERNOON OVER MIDDLE TN AND SRN KY. 
ADDITIONAL STORMS WILL ALSO BE POSSIBLE SEWD ALONG RETREATING
BOUNDARY OVER GA.  30-40 KTS OF WLY DEEP-LAYER SHEAR COUPLED WITH
THE MODERATE INSTABILITY SHOULD SUPPORT SEVERE STORMS CAPABLE OF
LARGE HAIL..DAMAGING WINDS AND PERHAPS A COUPLE OF TORNADOES.

...TX HILL COUNTRY AND EDWARDS PLATEAU...

ENVIRONMENT IS EXPECTED TO BECOME INCREASINGLY SUPPORTIVE OF FEW
DIURNAL SEVERE STORMS ALONG WRN EXTENSION OF STALLED FRONTAL
BOUNDARY.  HERE...DIABATIC HEATING AND MODEST BOUNDARY-LAYER
MOISTURE WILL CONTRIBUTE TO A MODERATELY UNSTABLE AIR MASS WITH
MLCAPES OF 1000-1500 J/KG.  THE STRONG DAYTIME HEATING ALONG WITH
FRONTAL CONVERGENCE AND PERHAPS SOME WEAK OROGRAPHIC FORCING SHOULD
BE SUFFICIENT TO INITIATE DEEP MOIST CONVECTION BY LATE AFTERNOON OR
EARLY EVENING. LARGELY UNIDIRECTIONAL 30-40 KT DEEP-LAYER SHEAR
SUGGESTS THE POTENTIAL FOR ROTATING STORMS CAPABLE OF LARGE HAIL AND
LOCALLY DAMAGING WINDS.

MORE ELEVATED TSTM DEVELOPMENT WILL BECOME INCREASINGLY LIKELY N OF
SURFACE FRONT WEDNESDAY NIGHT OVER THE CONCHO VALLEY/ERN PERMIAN
BASIN EWD INTO CNTRL TX AS WAA AND ISENTROPIC ASCENT INCREASE ALONG
STRENGTHENING SLY LLJ. SOME MARGINALLY SEVERE HAIL WILL BE POSSIBLE
WITH THE STRONGEST STORMS.

...MS INTO ERN TX...

DEWPOINTS IN THE 60S AND DAYTIME HEATING WILL SUPPORT MODERATE
INSTABILITY S OF FRONT WEDNESDAY AFTERNOON WITH MLCAPES OF 1000-2000
J/KG.  WEAK CAPPING AND FRONTAL CONVERGENCE SHOULD SUPPORT SCATTERED
TSTM DEVELOPMENT BY MID AFTERNOON WITH SOME POTENTIAL FOR ISOLATED
STRONG WIND GUSTS AND MARGINAL HAIL.  THE PRIMARY FACTOR LIMITING A
MORE ORGANIZED SEVERE THREAT APPEARS TO BE THE RATHER WEAK VERTICAL
SHEAR.

..MEAD.. 04/18/2006