DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1202 AM CDT MON OCT 07 2013 VALID 071200Z - 081200Z ...THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF THE UPPER CHESAPEAKE BAY NORTHWARD INTO ERN NY AND WRN NEW ENGLAND... ...SYNOPSIS... A VIGOROUS NEGATIVELY TILTED MID-LEVEL TROUGH IS FORECAST TO PIVOT ACROSS THE LOWER GREAT LAKES THROUGH THE NORTHEAST U.S. THROUGH DAYBREAK TUESDAY. SHOWERS AND ISOLATED THUNDERSTORMS ONGOING AT THE START OF THE PERIOD INVOF A COLD FRONT WILL SPREAD EWD ACROSS THE APPALACHIANS AND A LARGE PORTION OF THE NORTHEAST BY MONDAY EVENING. A FRONTAL LINE OF LOWER-TOPPED CONVECTION IS EXPECTED TO INTENSIFY AND BECOME THE PRIMARY FOCUS FOR STRONG TO SEVERE THUNDERSTORMS AS IT SWEEPS EWD ACROSS THE MID-ATLANTIC STATES NORTHWARD INTO PORTIONS OF NEW ENGLAND DURING THE DAY. ...MID-ATLANTIC STATES NORTHWARD INTO NEW ENGLAND... AS THE UPPER TROUGH ACCELERATES EASTWARD...TROPOSPHERIC WIND FIELDS WILL MARKEDLY STRENGTHEN OVER THE AREA AS LOW LEVEL MOISTURE --DUE IN PART TO A SLY 50-65 KT H85 JET-- INCREASES FROM SOUTH TO NORTH ACROSS THE AREA. SURFACE DEWPOINTS RANGING FROM NEAR 70 DEG AROUND THE MASON-DIXON LINE TO THE MID 60S IN THE ADIRONDACKS WILL CONTRIBUTE TO MARGINAL BUOYANCY DESPITE EXPECTED WIDESPREAD CLOUD COVER AHEAD OF THE FRONT. THE TRANSITION FROM A WEAK CONVECTIVE LINE ALONG THE FRONT TO A SURFACE-BASED SQUALL LINE IS EXPECTED BY MID-LATE MORNING AS STRONG FORCING FOR ASCENT AIDS IN ORGANIZING AN EXTENSIVE FRONTAL BAND OF SHOWERS/STORMS. FORECAST SOUNDINGS SHOW 0-1 KM SHEAR AROUND 40 KT WHICH WILL SUPPORT BOTH A WIND DAMAGE THREAT AND PERHAPS AN ISOLATED TORNADO THREAT WITH ANY LONGER-LIVED MESOVORTEX CIRCULATIONS THAT MAY DEVELOP. THE ACTIVITY IS FORECAST TO GRADUALLY WEAKEN BY EVENING OWING IN PART TO LOSS OF DAYTIME HEATING AND INCREASINGLY MARGINAL THERMODYNAMIC PROFILES TOWARDS THE NEW ENGLAND COAST. ...CAROLINAS AND VA TIDEWATER... LOW LEVEL SHEAR IS FORECAST TO WEAKEN DURING THE MORNING AS THE UPPER TROUGH MOVES AWAY FROM THE REGION THROUGH MIDDAY...CONCURRENT WITH WANING LARGE-SCALE ASCENT/WEAKENING DEEP SHEAR. DESPITE THESE LIMITING FACTORS...RICH LOW LEVEL MOISTURE MAY COMPENSATE FOR MODEST LAPSE RATE PROFILES FORECAST OVER THE REGION AND LEND THE POSSIBILITY FOR AN ISOLATED WIND DAMAGE THREAT WITH THE STRONGER STORMS.
Posted on: Mon, 07 Oct 2013 11:19:54 +0000
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