SWODY2
SPC AC 131728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT FRI APR 13 2007
VALID 141200Z - 151200Z
..THERE IS A MDT RISK OF SVR TSTMS ACROSS SERN LA...SERN
MS...CENTRAL AND SRN AL...PARTS OF WRN AND SWRN GA...AND THE FL
PANHANDLE...
..THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY EWD TO
SRN ATLANTIC STATES...
..SYNOPSIS...
AMPLIFIED UPPER PATTEN ACROSS THE CONTINENTAL U.S. WILL REMAIN
PROGRESSIVE ON SATURDAY AS A PACIFIC TROUGH MOVES INLAND OVER THE
WRN STATES. DOWNSTREAM TROUGH...INITIALLY EXTENDING FROM THE GREAT
LAKES SWWD TO THE SRN HIGH PLAINS...WILL BECOME MORE NEUTRALLY
ORIENTED AS IT TRACKS EWD THROUGH THE OH VALLEY AND GULF COAST
STATES. THIS LATTER TROUGH WILL BE THE MAIN UPPER FEATURE
SUPPORTING A SEVERE WEATHER THREAT FROM THE LOWER MS VALLEY EWD TO
THE SRN ATLANTIC COAST DURING DAY 2.
IN THE LOW LEVELS...SURFACE LOW SHOULD BE OVER THE ARKLATEX REGION
AT 12Z SATURDAY WITH COLD FRONT TRAILING SWWD INTO DEEP S TX. THESE
SURFACE FEATURES WILL SPREAD EWD ATTENDANT WITH PROGRESSIVE UPPER
TROUGH. SURFACE LOW IS EXPECTED TO DEEPEN SATURDAY AS IT TRACKS E
TOWARD AL BY 15/00Z...WITH STRONGEST DEEPENING OCCURRING THROUGH
SECOND HALF OF PERIOD...AS STRONG HEIGHT FALLS /120-180 METERS/
DEVELOP EWD ACROSS GULF COAST STATES. SURFACE LOW SHOULD REACH THE
ERN CAROLINAS BY 12Z SUNDAY.
..LOWER MS VALLEY EWD TO SRN ATLANTIC STATES...
STRONG UPPER TROUGH...NOW LOCATED OVER NM...IS FORECAST TO
DE-AMPLIFY SATURDAY AS IT MOVES NEWD INTO MID LEVEL CONFLUENT FLOW
REGIME OVER THE MIDWEST/SRN GREAT LAKES REGION. MEANWHILE...AN
UPSTREAM SHORT WAVE TROUGH...NOW LOCATED OVER LOWER CO RIVER
VALLEY...IS EXPECTED TO STRENGTHEN DURING DAY 2 WITHIN BASE OF ERN
LONGWAVE TROUGH AS IT PHASES WITH A NRN STREAM TROUGH. THIS PHASING
IS EXPECTED TO STRENGTHEN WIND FIELDS FROM THE LOWER MS VALLEY EWD
THROUGH THE GULF COAST STATES.
LOW LEVEL SLY WINDS IN ADVANCE OF COLD FRONT ARE EXPECTED TO PROVIDE
INFLUX OF GULF MOISTURE FROM THE LOWER MS VALLEY EWD TO NERN GULF
COAST STATES. ALTHOUGH LAPSE RATES ARE EXPECTED TO BE SOMEWHAT
WEAK...SURFACE DEWPOINTS IN THE MID-UPPER 60S WITH VALUES AROUND 70
ALONG THE GULF COAST COMBINED WITH SURFACE HEATING SHOULD RESULT IN
MUCAPE VALUES 1000-1500 J/KG. STRONGEST INSTABILITY SHOULD DEVELOP
ALONG THE COAST AND INLAND OVER THE SRN HALF OF THE GULF STATES.
AT 12Z SATURDAY...STRONG TO SEVERE STORMS ARE EXPECTED TO BE ONGOING
ALONG THE COLD FRONT...WITH DEEP LAYER SHEAR VECTORS PARALLEL TO
FRONT SUGGESTING A DAMAGING WIND AND HAIL THREAT WITH THIS EARLY
ACTIVITY. DIFFLUENT FLOW DOWNSTREAM ATOP DESTABILIZING WARM SECTOR
SUGGESTS THE POTENTIAL FOR ISOLATED TSTMS TO DEVELOP IN ADVANCE OF
STORMS ALONG THE COLD FRONT. SHEAR VECTORS OVER THE WARM SECTOR
SHOULD BE MORE CONDUCIVE FOR DISCRETE SUPERCELLS WITH THREAT FOR
TORNADOES...DAMAGING WINDS AND HAIL.
STRONGER HEIGHT FALLS AND STRENGTHENING WIND FIELDS EXPECTED FROM
LATE AFTERNOON INTO SATURDAY NIGHT SHOULD COMPENSATE FOR THE WEAKER
LAPSE RATES/INSTABILITY AND SUPPORT AN INCREASE IN SEVERE STORMS...
SOME STRONG TO SIGNIFICANT...FROM THE MS DELTA REGION INTO AL AND
EWD. ALL SEVERE TYPES SHOULD BE EXPECTED THROUGH LATE IN THE PERIOD
AS ACTIVITY SPREADS E TOWARD NRN FL TO THE CAROLINAS BY 12Z SUNDAY.
.PETERS.. 04/13/2007
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