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.