DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 121732
SWODY2
SPC AC 121730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT WED JUN 12 2013

VALID 131200Z - 141200Z

...THERE IS A MDT RISK OF SVR TSTMS FROM ERN VA...MD...DEL...SRN
NJ...SERN PA...

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE MID
ATLANTIC...

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE NRN HIGH
PLAINS...

...SYNOPSIS...

A SHORTWAVE TROUGH OVER THE NRN PLAINS IS CRESTING CNTRL U.S. UPPER
RIDGE...AND WILL RESULT IN AMPLIFICATION OF DOWNSTREAM MEAN TROUGH
ACROSS THE MID ATLANTIC AND NERN U.S. THURSDAY. MEANWHILE...THE
UPPER TROUGH OVER THE PACIFIC NW WILL MOVE SLOWLY EWD INTO THE NRN
INTERMOUNTAIN REGION.

SFC CYCLONE WILL SHIFT EWD THROUGH THE MID ATLANTIC IN ASSOCIATION
WITH DEEPER FORCING ATTENDING THE ERN U.S. SHORTWAVE TROUGH. BY 12Z
THURSDAY A COLD FRONT SHOULD EXTEND FROM THE SFC LOW OVER PA...SWWD
INTO THE OH AND LOWER MS VALLEY REGION. THIS BOUNDARY WILL ADVANCE
SEWD DURING THE DAY...REACHING THE ATLANTIC SEABOARD LATER THURSDAY
EVENING WITH TRAILING PORTION EXTENDING INTO THE SERN STATES. WARM
FRONT EXTENDING EWD FROM THE LOW WILL LIFT SLOWLY NWD THROUGH THE
MID ATLANTIC STATES...LIKELY AS FAR NORTH AS NJ.

...MID ATLANTIC REGION...

SWLY WINDS AHEAD OF THE DEVELOPING CYCLONE WILL TRANSPORT UPPER 60S
DEWPOINTS THROUGH PRE-FRONTAL WARM SECTOR BENEATH RESIDUAL PLUME OF
7 C/KM MID LEVEL LAPSE RATES. THE ATMOSPHERE IS EXPECTED TO BECOME
MODERATELY UNSTABLE AS DIABATIC WARMING COMMENCES WITH MLCAPE FROM
2000-3000 J/KG POSSIBLE. MEANWHILE...STRONGER WINDS IN THE 700-500
MB LAYER ROUNDING BASE OF AMPLIFYING SHORTWAVE TROUGH WILL SPREAD
OVER THE WARM SECTOR DURING THE AFTERNOON. STRENGTHENING DEEP LAYER
WLY WINDS SHOULD RESULT IN A DOWNSLOPING REGIME IMMEDIATELY EAST OF
SRN/CNTRL APPALACHIANS...SUGGESTING IT MIGHT BE DIFFICULT FOR ANY
ONGOING STORMS SURVIVE CROSSING THE MOUNTAINS. HOWEVER...PRE FRONTAL
TROUGH/CONVERGENCE AXIS WILL LIKELY EVOLVE FARTHER EAST FROM THE
CNTRL CAROLINAS INTO CNTRL/ERN VA. ADDITIONAL STORMS WILL LIKELY
DEVELOP ALONG THIS CONVERGENCE ZONE OR AS COLD FRONT OVERTAKES THE
DESTABILIZING WARM SECTOR. DEEP LAYER WIND PROFILES WILL BE LARGELY
UNIDIRECTIONAL WITH SWLY FLOW IN THE SFC-3 KM LAYER SOUTH OF SFC
LOW. THE 0-6 KM VERTICAL SHEAR OF 30-40 KT WILL SUPPORT POTENTIAL
FOR A FEW SUPERCELLS ESPECIALLY WITHIN 2-3 HOURS OF INITIATION.
HOWEVER...TENDENCY MAY BE FOR SOME OF THIS ACTIVITY TO EVOLVE INTO
LINE SEGMENTS WITH LEWP/BOW STRUCTURES. WIDESPREAD DAMAGING WIND AND
LARGE HAIL ARE EXPECTED TO BE THE MAIN THREATS...THOUGH A FEW
TORNADOES CANNOT BE RULED OUT.

...SERN STATES...

LOW 70S BOUNDARY LAYER DEWPOINTS ARE IN PLACE AND WILL SUPPORT
MODERATE INSTABILITY /2000-2500 J/KG MLCAPE/ AS THE SFC LAYER WARMS
AND DESTABILIZES DURING THE AFTERNOON. A BELT OF STRONGER MID-UPPER
WINDS WILL DROP SEWD OVER THE WARM SECTOR AS THE UPPER TROUGH
AMPLIFIES THE EAST OF THIS REGION. THIS WILL RESULT IN NWLY DEEP
LAYER WINDS AND EFFECTIVE SHEAR OF 30-35 KT THAT WILL BECOME AT
LEAST MARGINALLY SUPPORTIVE OF ORGANIZED STORMS. CURRENT INDICATIONS
ARE THAT A FEW STORMS MAY BE ONGOING OVER THE TN VALLEY REGION...AND
ADDITIONAL ACTIVITY MAY DEVELOP/INTENSIFY ALONG THE SWD MOVING
OUTFLOW BOUNDARIES. DAMAGING WIND AND LARGE HAIL WILL BE THE MAIN
THREATS.

..ERN MT AND THE NRN HIGH PLAINS REGION...

COLD FRONT AND ASSOCIATED UPPER TROUGH WILL ADVANCE EWD INTO A
DESTABILIZING AFTERNOON AIRMASS. EXPECT ISOLATED THUNDERSTORMS TO
DEVELOP -- INITIALLY OVER CENTRAL AND ERN MT AND ADJACENT NERN WY.
WHILE STRONG CAPPING -- OWING TO THE PRECEDING INFLUENCE OF UPPER
RIDGE -- SUGGESTS THAT COVERAGE WILL BE LIMITED...STORMS WHICH DO
DEVELOP WILL LIKELY BECOME SEVERE/SUPERCELLULAR GIVEN MODERATE
INSTABILITY AND AMPLE VEERING/SHEAR. HAIL AND DAMAGING WINDS WILL
BE THE PRIMARY SEVERE THREATS THROUGH THE AFTERNOON. STORMS SHOULD
SPREAD EWD ACROSS ERN MT TOWARD WRN SD INTO THE EVENING...AS A SELY
LOW-LEVEL JET INCREASES ACROSS THE HIGH PLAINS. SHEAR WILL CONTINUE
TO FAVOR SEVERE POTENTIAL...WITH CONTINUED THREAT FOR DAMAGING WINDS
AND HAIL AND POSSIBLY AN ISOLATED TORNADO.

..DIAL.. 06/12/2013

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