SWODY1
SPC AC 071218
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0718 AM CDT THU AUG 07 2008
VALID 071300Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF PA/NY/NJ/CT/MA...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY INTO
THE CAROLINAS...
...LOWER MS VALLEY...SOUTHEAST STATES...CAROLINAS...
A LARGE UPPER RIDGE WILL REMAIN IN PLACE TODAY OVER THE ROCKIES AND
GREAT BASIN...WHILE AN UPPER TROUGH AMPLIFIES OVER THE EASTERN
STATES. THE STRENGTHENING EASTERN TROUGH WILL RESULT IN A SURFACE
COLD FRONT SURGING SOUTHWARD INTO THE SOUTHEAST STATES...PROVIDING
THE FOCUS FOR NUMEROUS AFTERNOON THUNDERSTORMS. EARLY VISIBLE
SATELLITE IMAGERY SUGGEST THE POTENTIAL FOR STRONG DAYTIME
HEATING...WHICH COMBINED WITH DEWPOINTS NEAR 70F WILL CREATE A VERY
UNSTABLE AIRMASS /MLCAPE VALUES OF 2000-3000 J/KG/. INCREASING MID
LEVEL NORTHWESTERLY WINDS OF 25-40 KNOTS ACROSS THE REGION WILL
YIELD SUFFICIENT DEEP LAYER VERTICAL SHEAR FOR ORGANIZED MULTICELL
OR OCCASIONAL SUPERCELL STORMS CAPABLE OF DAMAGING WINDS AND HAIL.
STORMS WILL LIKELY MERGE INTO CLUSTERS FROM AR/LA INTO THE CAROLINAS
WITH A CONTINUING THREAT OF SCATTERED SEVERE ACTIVITY THROUGH THE
EARLY EVENING.
...NJ/PA/NY/MA/CT...
COLD MID LEVEL TEMPERATURES HAVE OVERSPREAD MUCH OF THE NORTHEAST
UNITED STATES THIS MORNING WITH 500MB TEMPS OF -12 TO -16 SHOWN ON
REGIONAL RAOB DATA. VISIBLE SATELLITE IMAGERY INDICATES THAT MOSTLY
CLEAR SKIES WILL OCCUR THIS MORNING OVER EASTERN NY/PA WHERE
TEMPERATURES SHOULD WARM INTO THE 70S AND LOWER 80S. RESIDUAL
DEWPOINTS IN THE LOWER 60S WILL YIELD MLCAPE VALUES OF 1500-2000
J/KG BY EARLY/MID AFTERNOON. MOST OPERATIONAL AND MESOSCALE MODEL
MEMBERS SUGGEST THAT A CLUSTER OF STRONG/SEVERE STORMS WILL DEVELOP
TODAY OVER SOUTHEAST NY/NORTHEAST PA/NORTHERN NJ AND SPREAD EASTWARD
INTO SOUTHWEST NEW ENGLAND. LOW LEVEL VERTICAL SHEAR IS RATHER
WEAK. HOWEVER...SUFFICIENT MID LEVEL FLOW AND STEEP LAPSE RATES
WILL PROMOTE A RISK OF HAIL AND DAMAGING WINDS IN STRONGER CELLS.
STORMS SHOULD DIMINISH QUICKLY AFTER SUNSET.
..AZ...
SCATTERED TSTMS MAY DEVELOP ACROSS THIS REGION DURING AFTERNOON
HOURS. ACTIVITY INITIALLY SHOULD FAVOR HIGHER TERRAIN...BUT SOME
TSTMS SHOULD MIGRATE OVER VALLEYS/DESERT AREAS LATE AFTERNOON. FCST
BUOYANCY APPEARS MRGL -- WITH WEAK MID-UPPER LAPSE RATES LIMITING
MLCAPES TO UNDER 1000 J/KG MOST AREAS. HOWEVER... DEEP/WELL-MIXED
SUBCLOUD LAYERS SHOULD SUPPORT POTENTIAL FOR STG/ISOLATED SVR
GUSTS...PARTICULARLY IF STORMS CAN CONCENTRATE SUFFICIENTLY TO
DEVELOP AMALGAMATED OUTFLOW.
...NWRN CONUS...
WIDELY SCATTERED TSTMS ARE EXPECTED TO FORM DURING AFTERNOON AS STG
HEATING CONTRIBUTES TO STEEPENING LOW-MIDLEVEL LAPSE RATES...IN
ENVIRONMENT OF FAVORABLE LOW LEVEL MOISTURE OVER CASCADES. STG SWLY
FLOW ALOFT AHEAD OF PACIFIC TROUGH SHOULD ENCOURAGE MOTION OF THIS
ACTIVITY ACROSS DRIER AND MORE WELL-MIXED AIR MASS FATHER E...WITH
POTENTIAL FOR HAIL AND ISOLATED GUSTS NEAR SVR LEVELS.
..HART/JEWELL/EDWARDS.. 08/07/2008
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