[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 300538
SWODY2
SPC AC 300536

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1136 PM CST WED NOV 29 2006

VALID 011200Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER OH VALLEY EWD
THROUGH THE MIDDLE ATLANTIC STATES AND NEW ENGLAND...

...SYNOPSIS...

INTENSE...NEGATIVELY-TILTED SHORT WAVE TROUGH INITIALLY OVER THE
LOWER OH VALLEY WILL RAPIDLY TRANSLATE NEWD THROUGH THE ST. LAWRENCE
VALLEY WITH 250-300M HEIGHT FALLS SPREADING NEWD THROUGH THE
MIDDLE/UPPER OH VALLEY AND NERN STATES.  IN THE LOW-LEVELS...
DEEPENING SURFACE LOW WILL DEVELOP FROM THE MIDDLE OH VALLEY NEWD
THROUGH THE UPPER GREAT LAKES INTO THE GULF OF ST. LAWRENCE WITH
TRAILING COLD FRONT SWEEPING EWD THROUGH THE APPALACHIANS...PIEDMONT
AND COASTAL PLAIN.

...UPPER OH VALLEY EWD THROUGH THE MIDDLE ATLANTIC STATES AND NEW
ENGLAND...

LARGE-SCALE PATTERN APPEARS SUPPORTIVE OF A LOW INSTABILITY/HIGH
SHEAR SERIAL-TYPE DERECHO EVENT OVER PARTS OF THE REGION FRIDAY INTO
FRIDAY NIGHT.

STRONGLY FORCED...LOW-TOPPED CONVECTIVE LINE IS EXPECTED TO BE
ONGOING FRIDAY MORNING FROM VICINITY OF SURFACE LOW OVER IND/WRN OH
SWD ALONG COLD FRONT INTO MIDDLE TN...DRIVEN BY INTENSE LARGE-SCALE
FORCING ASSOCIATED WITH EJECTING UPPER WAVE.  SSWLY 50-60KT LLJ
INITIALLY FROM AL/GA INTO THE UPPER OH VALLEY WILL SHIFT EWD THROUGH
THE DAY...TRANSPORTING AN INCREASINGLY MOIST BOUNDARY LAYER NWD INTO
THE REGION.  THIS INCREASE IN MOISTURE COUPLED WITH STEEPENING
MID-LEVEL LAPSE RATES ARE EXPECTED TO CONTRIBUTE TO DESTABILIZATION
OF PRE-FRONTAL AIR MASS WITH STRONGEST INSTABILITY /MUCAPES
APPROACHING 500-900 J PER KG/ DEVELOPING ACROSS PA AND NY FRIDAY
AFTERNOON.

100-120KT MID-LEVEL JET STREAK ALONG IMMEDIATE DOWNSTREAM POSITION
OF TROUGH BASE AND 60-70KT WINDS AS LOW AS 1-2 KM AGL /PER FORECAST
SOUNDINGS/ INDICATE THAT EVEN WEAK CONVECTIVE DOWNDRAFTS WILL BE
CAPABLE OF DAMAGING WINDS.  AS SUCH...EXPECT THAT THE WIND DAMAGING
THREAT WILL EXIST FROM THE ONSET OF THE FORECAST OVER OH SWD INTO
KY/WV...WITH THIS THREAT LIKELY INCREASING CONSIDERABLY BY AFTERNOON
OVER NY/PA AS CONVECTIVE LINE ENCOUNTERS AN INCREASINGLY UNSTABLE
AIR MASS.  EMBEDDED BOWING/LEWP STRUCTURES WILL BE CAPABLE OF
CORRIDORS OF DAMAGING WINDS...ESPECIALLY GIVEN THE FORECAST 50-60+KT
STORM MOTIONS. THE STRONGER INSTABILITY OVER NY/PA MAY EVEN SUPPORT
EMBEDDED SUPERCELLS WITH A THREAT OF ISOLATED TORNADOES GIVEN THE
STRONG LOW-LEVEL SHEAR AND LOW LCL HEIGHTS.

EXPECT THIS STRONGLY FORCED...FAST MOVING CONVECTIVE LINE TO SWEEP
THROUGH THE HUDSON VALLEY AND DE RIVER VALLEY LATE FRIDAY AFTERNOON
OR EARLY EVENING...AND MUCH OF NEW ENGLAND FRIDAY NIGHT.  WIDESPREAD
DAMAGING WINDS WILL REMAIN POSSIBLE THROUGH AT LEAST THE EVENING
HOURS AS BOUNDARY LAYER REMAINS SOMEWHAT TURBULENTLY MIXED.

SHOULD FUTURE OBSERVATIONS AND/OR MODEL GUIDANCE INDICATE MORE
INSTABILITY THAN IS CURRENTLY FORECAST...AN UPGRADE TO MODERATE RISK
MAY BECOME NECESSARY.

..MEAD.. 11/30/2006