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Mar 11, 2014 1730 UTC Day 2 Convective Outlook

March 11, 2014

Mar 11, 2014 1730 UTC Day 2 Convective Outlook

day2otlk

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.

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