Major Severe Weather Outbreak for the Mid-Atlantic/NE US on Saturday

Published on Friday, 07 September 2012 12:50

David Reimer

0 Comments

The Storm Prediction Center has issued a significant risk of severe weather for much of the Northeast United States and portions of the Mid-Atlantic for Saturday. Honestly, model data is pretty concerning regarding the potential for a high-impact severe weather event. Wind fields and instability support a derecho with widespread 75-90 MPH winds and the possibility of strong, fast moving tornadoes. You expect this kind of system to occur over the Southern Plains, yet it is going to happen over the northeast United States. This is expected to be a dangerous severe weather event. If you have family of friends in the affected areas, you need to let them know to watch the weather tomorrow. This is not going to be something folks up there are accustomed to seeing.

Right now, the highest risk zone is highlighted by the red shading on the left half of the graphic and the purple shading on the right. Notice several metropolitan areas are included or very close to this highest risk area. Here is the severe weather outlook from the Storm Prediction Center.

   ...DAMAGING SEVERE THUNDERSTORMS ARE EXPECTED ACROSS THE NORTHEASTERN U.S. SATURDAY...

   POTENTIALLY SIGNIFICANT DAMAGING WIND EVENT IS EXPECTED ACROSS MUCH
   OF THE NERN U.S. SATURDAY.  LATEST MODEL GUIDANCE...ESPECIALLY THE
   NAM/ECMWF...SUGGEST SHORT-WAVE TROUGH OVER THE UPPER GREAT LAKES
   WILL DIG INTO LOWER MI BY 08/12 BEFORE EJECTING NEWD IN A NEGATIVELY
   TILTED FASHION AND DEEPENING OVER SERN ONTARIO/WRN QUEBEC.  90-120M
   12HR HEIGHT FALLS WILL SPREAD ACROSS WRN/UPSTATE NY DURING THE DAY
   ENSURING A STRONGLY FORCED AND CONVECTIVELY-ACTIVE COLD FRONT.  THIS
   EVOLUTION SUGGESTS A FRONTAL INTRUSION THAT WILL INDUCE A BAND OF
   SEVERE THUNDERSTORMS AS IT SURGES ACROSS THE NRN MIDDLE ATLANTIC
   REGION INTO NEW ENGLAND.

   ALL INDICATIONS FAVOR A SQUALL ALONG THE WIND SHIFT AT SUNRISE FROM
   SRN ONTARIO SWD ACROSS OH...TRAILING INTO THE TN VALLEY.  THIS
   ACTIVITY IS EXPECTED TO INTENSIFY AS IT MOVES INTO WRN
   NY/PA...ESPECIALLY BY 18Z AS BOUNDARY LAYER BEGINS TO WARM. 
   ALTHOUGH FORECAST LAPSE RATES ARE NOT PARTICULARLY STEEP BOUNDARY
   LAYER AIRMASS IS FAIRLY MOIST ATTM WITH UPPER 60S-70F SFC DEW POINTS
   IN PLACE ACROSS THE MIDDLE ATLANTIC REGION.  THERE IS LITTLE REASON
   TO BELIEVE THIS AIRMASS WILL NOT SPREAD NWD ACROSS PA/NJ INTO
   UPSTATE NY AHEAD OF THE COLD FRONT AND AMPLE MOISTURE/INSTABILITY
   WILL SPREAD NWD TOWARD THE CANADIAN BORDER TO SUPPORT ROBUST
   UPDRAFTS WITHIN A STRONGLY SHEARED ENVIRONMENT.

   OF PARTICULAR CONCERN IS THE EXPECTED MID LEVEL JET THAT SHOULD
   INTENSIFY AS IT EJECTS ACROSS WRN PA TO SPEEDS IN EXCESS OF 70KT
   OVER UPSTATE NY BY 09/00Z.  WITH DEEPENING SFC LOW OVER SERN ONTARIO
   FORECAST SHEAR PROFILES BECOME QUITE FAVORABLE FOR SUSTAINING
   ORGANIZED UPDRAFTS.  WHILE A DAMAGING SQUALL LINE IS EXPECTED ALONG THE ADVANCING COLD FRONT...ENVIRONMENTAL SHEAR WILL BECOME QUITE
   FAVORABLE FOR PRE-FRONTAL SUPERCELLS AND EMBEDDED SUPERCELLS WITHIN
   THE MAIN SQUALL LINE.  FORECAST SOUNDINGS FROM NRN NJ NWD THROUGH THE HUDSON VALLEY SUGGEST TORNADOES ARE POSSIBLE IF DISCRETE
   SUPERCELLS CAN EVOLVE AHEAD OF THE MAIN LINE AND WITH CIRCULATIONS
   WITHIN THE LINE.  LATEST MODEL GUIDANCE SUGGESTS THE BACK EDGE OF
   THE PRIMARY SQUALL LINE WILL ADVANCE INTO THE HUDSON VALLEY BY LATE
   AFTERNOON TRAILING SWWD INTO CNTRL VA BY 09/00Z WITH SUBSEQUENT
   MOVEMENT ACROSS MUCH OF NEW ENGLAND BY 06Z.