DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 111711
SWODY2
SPC AC 111710

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1210 PM CDT TUE MAR 11 2014

VALID 121200Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR PORTIONS OF THE MIDDLE
ATLANTIC...

...SYNOPSIS...
WATER VAPOR LOOPS IMPLY A MID-LEVEL DISTURBANCE CURRENTLY EMERGING
OVER THE CNTRL PLAINS...AND THIS FEATURE IS FORECAST TO SHIFT EWD
AND REACH THE MID MS VALLEY BY THE BEGINNING OF D2/WED. AS IT DOES
SO...IT WILL PHASE WITH A NRN-STREAM SHORTWAVE IMPULSE DIGGING SSEWD
FROM ONTARIO AND MANITOBA. THE RESULTING PERTURBATION WILL BE A
POTENT...HIGH-AMPLITUDE SHORTWAVE TROUGH THAT WILL ADVANCE EWD
ACROSS THE ERN UNITED STATES. HIGH-MAGNITUDE...LARGE-SCALE UPWARD
MOTION PRECEDING THIS TROUGH WILL BE AUGMENTED BY STRONG UPPER
DIVERGENCE ATTENDANT TO A COUPLED UPPER JET STRUCTURE AND
INTENSIFYING LLJ OVER THE MID ATLANTIC AND NORTHEAST. THIS WILL
SUPPORT THE ENEWD/NEWD DEVELOPMENT AND INTENSIFICATION OF A FRONTAL
CYCLONE FROM THE UPPER OHIO VALLEY TO THE ATLANTIC WATERS OFF THE
SRN NEW ENGLAND COAST. A STRONG COLD FRONT TRAILING SSW OF THE
CYCLONE WILL SWEEP EWD ACROSS THE SERN STATES AND MID
ATLANTIC...WHILE STRONG POLEWARD MASS FLUXES PRECEDING THE CYCLONE
ALLOW A WARM SECTOR TO EXTEND INTO PORTIONS OF ERN PA AND NJ.

...THE MIDDLE ATLANTIC...
THE AIR MASS IN ADVANCE OF THE STRONG COLD FRONT WILL BECOME
MARGINALLY UNSTABLE -- E.G. MLCAPE AROUND 300-600 J/KG -- DURING THE
AFTERNOON. THIS WILL BE IN RESPONSE TO THE COMBINATION OF /1/ AT
LEAST PARTIAL INSOLATION IN SOME AREAS IN THE WAKE OF
EARLY-DAY...WARM-ADVECTION-ENCOURAGED CLOUDS/SHOWERS ASSOCIATED WITH
THE STRENGTHENING LLJ...AND /2/ STRONG NWD FLUXES OF RELATIVELY
HIGHER THETA-E AIR IN THE BOUNDARY LAYER WITH SFC DEWPOINTS IN THE
MIDDLE 50S. THE NRN EXTENT OF THE WARM/BUOYANT SECTOR WILL BE
MODULATED TO SOME EXTENT BY DOWNWARD-DIRECTED SENSIBLE HEAT FLUXES
WITHIN THE SFC LAYER ATOP THE ONGOING SNOW PACK IN NRN PA AND NRN
NJ. REGARDLESS...DIURNALLY ENHANCED BUOYANCY SHOULD ALLOW
THUNDERSTORMS TO INCREASE IN NUMBER AND INTENSITY ALONG THE COLD
FRONT AS IT ADVANCES FROM SERN OHIO/ERN KY INTO WRN WV AND WRN PA BY
MID-DAY...WITH THIS ACTIVITY QUICKLY SPREADING EWD/NEWD THROUGH THE
AFTERNOON.

WITH THE EXIT REGION OF A 70-90-KT H5 JET CORE OVERSPREADING THE
WARM SECTOR BUOYANCY ABOVE A SWLY LLJ INCREASING TO 50-60 KT...WIND
PROFILES WILL BE FAVORABLE FOR LOW-TOPPED...ORGANIZED CONVECTION.
THUNDERSTORMS ARE EXPECTED TO BECOME ORGANIZED INTO FAST MOVING
QUASI-LINEAR SEGMENTS WITH EMBEDDED LEWP STRUCTURES INVOF THE COLD
FRONT. STRONG CONVECTIVE MOMENTUM TRANSPORT WILL SUPPORT THE
POTENTIAL FOR DAMAGING WIND GUSTS...WITH THIS POTENTIAL BOLSTERED BY
THE STRONG CROSS-FRONTAL...SYNOPTIC PRESSURE RISE-FALL COUPLET.
STRONG LOW-LEVEL SHEAR -- E.G. AROUND 30-40 KT OF 0-1-KM BULK
SHEAR -- WILL SUPPORT SOME POTENTIAL FOR LINE-EMBEDDED MESOVORTICES
TO PRODUCE TORNADOES.

THE GREATEST SVR POTENTIAL WILL EXTEND ACROSS THE ERN PANHANDLE OF
WV INTO NRN VA...CNTRL/WRN MD...THE DISTRICT OF COLUMBIA...AND
S-CNTRL PA...WHICH MAY HAVE THE GREATEST OPPORTUNITY TO EXPERIENCE
PRE-FRONTAL INSOLATION. THERE WILL BE SOME POTENTIAL FOR A MORE
WIDESPREAD SVR-WIND EVENT TO TAKE PLACE IN THESE AREAS...POTENTIALLY
WARRANTING HIGHER SVR PROBABILITIES IN SUBSEQUENT OUTLOOKS.
HOWEVER...SUCH POTENTIAL WILL BE PREDICATED ON THE DEGREE OF
INSOLATION-ENHANCED STEEPENING OF LOW-LEVEL LAPSE RATES...FOR WHICH
SOME UNCERTAINTY EXISTS. STORMS ARE EXPECTED TO MOVE OFF THE COAST
AS THE FRONT MOVES OFFSHORE.

..COHEN.. 03/11/2014

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