DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 150832
SWODY3
SPC AC 150830

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CST FRI NOV 15 2013

VALID 171200Z - 181200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE TN AND OH
VALLEYS AND GREAT LAKES AREAS...

...SYNOPSIS...

A SHORTWAVE TROUGH WITH ATTENDANT STRONG UPPER JET EMBEDDED WITHIN
BASE OF THE SYNOPTIC TROUGH WILL EJECT NEGATIVELY TILTED THROUGH THE
MID MS AND OH VALLEYS SUNDAY...REACHING A PORTION OF THE NERN U.S.
TOWARD THE END OF THE PERIOD. THIS FEATURE WILL INDUCE A SFC CYCLONE
THAT IS FORECAST TO UNDERGO SIGNIFICANT DEEPENING AS IT MOVES NEWD
FROM THE UPPER MS VALLEY INTO THE GREAT LAKES SUNDAY AFTERNOON. COLD
FRONT TRAILING FROM THE LOW WILL SWEEP THROUGH THE MID MS...OH AND
TN VALLEYS...WHILE A WARM FRONT LIFTS NWD THROUGH THE OH VALLEY AND
GREAT LAKES.

...OH AND TN VALLEY REGIONS...

A STRONG 50+ KT SWLY LLJ WILL ADVECT PARTIALLY MODIFIED GULF AIR
WITH DEWPOINTS IN THE UPPER 50S TO LOW 60S INTO THE OH VALLEY AND
GREAT LAKES REGION WITH MID 60S LIKELY FARTHER SOUTH ACROSS THE TN
VALLEY AREA. THE MOISTURE RETURN WILL BE ACCOMPANIED BY WIDESPREAD
CLOUDS THAT WILL LIMIT DIABATIC HEATING OF THE BOUNDARY LAYER IN
MUCH OF PRE-FRONTAL WARM SECTOR. MOREOVER...AREAS OF SHOWERS AND A
FEW THUNDERSTORMS WILL PROBABLY BE ONGOING OVER A PORTION OF THE OH
VALLEY WARM SECTOR. THUS THE PRIMARY DESTABILIZATION MECHANISM WILL
PROBABLY BE MOISTURE ADVECTION...BUT SFC BASED INSTABILITY WILL
LIKELY REMAIN SOMEWHAT MARGINAL /MLCAPE AOB 500 J/KG/...ESPECIALLY
WITH NWD AND EWD EXTENT INTO THE OH VALLEY AND GREAT LAKES.

NEVERTHELESS...THE DEEPENING CYCLONE WILL BE ACCOMPANIED BY AN
INCREASE IN FRONTOGENETIC FORCING ALONG THE COLD FRONT SWEEPING EWD
THROUGH THE OH VALLEY. STORMS MAY INCREASE DURING THE DAY ALONG
PRE-FRONTAL WARM CONVEYOR BELT BENEATH DIFFLUENT UPPER JET EXIT
REGION. OTHER STORMS WILL INITIATE ALONG STRENGTHENING COLD FRONT.
POTENTIAL WILL EXIST FOR PRE-FRONTAL STORMS TO DEVELOP SUPERCELL
STRUCTURES GIVEN STRENGTH OF VERTICAL SHEAR AND SIZE OF HODOGRAPHS
ALONG LLJ...BUT EXTENT OF ANY TORNADO THREAT WILL DEPEND ON DEGREE
OF BOUNDARY LAYER DESTABILIZATION. OTHERWISE...STORMS WILL LIKELY
EVOLVE INTO LINES ALONG THE COLD FRONT WITH A THREAT FOR WIDESPREAD
DAMAGING WIND AS THE ACTIVITY DEVELOPS EWD THROUGH THE OH AND TN
VALLEY REGIONS.

...NY AND PA...
STORMS WILL EVENTUALLY OUTPACE THE MOIST AXIS SUNDAY NIGHT AND
ENCOUNTER MUCH WEAKER INSTABILITY AS THEY APPROACH THE NERN STATES.
HOWEVER...AT LEAST A MODEST THREAT FOR ISOLATED DAMAGING WIND WITH
REMAINING LOW TOPPED CONVECTION CANNOT BE RULED OUT LATE THIS
PERIOD.

..DIAL.. 11/15/2013

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