DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 171732
SWODY2
SPC AC 171731

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT MON SEP 17 2012

VALID 181200Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE SERN
STATES THROUGH THE MID ATLANTIC AND NERN U.S....

...SYNOPSIS...

SYNOPTIC UPPER PATTERN IS IN THE PROCESS OF AMPLIFICATION...AND THIS
TREND WILL CONTINUE INTO EARLY TUESDAY. A NRN STREAM UPPER TROUGH
FROM SCNTRL CANADA INTO THE NRN PLAINS/UPPER MS VALLEY WILL AMPLIFY
ACROSS THE OH VALLEY AND GREAT LAKES. THIS FEATURE WILL SUBSEQUENTLY
EJECT NEWD THROUGH THE NERN STATES AND SERN CANADA TUESDAY NIGHT. AS
NRN BRANCH TROUGH AMPLIFIES...THE SRN STREAM UPPER LOW OVER TX /AS
WELL AS THE LEAD IMPULSE OVER LA/ WILL SHEAR NEWD AND DEAMPLIFY
WHILE ACCELERATING INTO THE SRN APPALACHIANS AND THE MID ATLANTIC
REGION. PRIMARY SFC LOW WILL DEEPEN OVER THE LOWER GREAT LAKES AND
LIFT NWD INTO QUEBEC WHILE TRAILING COLD FRONT ADVANCES THROUGH THE
ERN STATES...REACHING THE ATLANTIC SEABOARD LATER TUESDAY NIGHT. A
WARM FRONT SHOULD LIFT NWD THROUGH THE MID ATLANTIC...REACHING SRN
NEW ENGLAND BY TUESDAY EVENING.


...MID ATLANTIC THROUGH PORTIONS OF THE NERN STATES...

IN WAKE OF NWD ADVANCING WARM FRONT...RICH GULF MOISTURE WITH UPPER
60S TO NEAR 70F DEWPOINTS WILL ADVECT THROUGH WARM SECTOR ALONG
STRENGTHENING 50+ KT LLJ. WIDESPREAD CLOUDS WITH AREAS OF RAIN AND
THUNDERSTORMS WILL LIKELY BE ONGOING ALONG WARM CONVEYOR BELT AND
WITHIN PLUME OF DEEPER SUBTROPICAL MOISTURE...ESPECIALLY IN WRN
PORTION OF WARM SECTOR. SOME OF THIS ACTIVITY COULD POSE A THREAT OF
MAINLY ISOLATED DAMAGING WIND FROM THE WRN CAROLINAS INTO WRN VA.
CLOUDS AND AREAS OF RAIN WILL CONTRIBUTE TO WEAK MID LEVEL LAPSE
RATES AND INSTABILITY...POSSIBLY SERVING AS A LIMITING FACTOR. THE
MOST FAVORABLE SHEAR/INSTABILITY PARAMETER SPACE FOR SEVERE STORMS
IS EXPECTED EVOLVE OVER THE MID ATLANTIC REGION ALONG STRENGTHENING
LLJ AND WHERE A FEW CLOUD BREAKS WILL PROMOTE AT LEAST MODEST
BOUNDARY LAYER DESTABILIZATION WITH 500-1000 J/KG MLCAPE POSSIBLE.

STORMS ARE EXPECTED TO INTENSIFY AS THEY DEVELOP EWD THROUGH THE
DESTABILIZING WARM SECTOR. MIXED CONVECTIVE MODES ARE LIKELY
INCLUDING LINES WITH EMBEDDED SUPERCELLS/BOWING SEGMENTS. A FEW
DISCRETE SUPERCELLS MAY ALSO OCCUR IF SUFFICIENT BOUNDARY LAYER
WARMING OCCURS. DAMAGING WIND AND A FEW TORNADOES WILL BE THE
PRIMARY THREATS. THIS REGION WILL CONTINUE TO BE MONITORED FOR A
POSSIBLE MODERATE RISK IF IT BEGINS TO APPEAR THAT MORE INSTABILITY
WILL DEVELOP THAN CURRENTLY ANTICIPATED.

...SERN STATES...

OTHER STORMS WILL LIKELY CONTINUE DEVELOPING IN PRE-FRONTAL WARM
SECTOR WHERE DEEP SHEAR WILL REMAIN AT LEAST MARGINALLY SUFFICIENT
FOR ORGANIZED STORMS...BUT LOW LEVEL FLOW/SHEAR WILL BE MUCH WEAKER
THAN FARTHER NE AS THE LLJ LIFTS INTO THE MID ATLANTIC AREA.
DEPENDING ON AMOUNT OF CLOUD BREAKS AND DIABATIC WARMING...SOME OF
THIS ACTIVITY MAY INTENSIFY AND POSE A THREAT OF ISOLATED STRONG TO
DAMAGING WIND GUSTS.

..DIAL.. 09/17/2012

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