DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 311657
SWODY2
SPC AC 311656

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1156 AM CDT THU MAY 31 2012

VALID 011200Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE ERN U.S....

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE TX PANHANDLE...

...ERN U.S...

AN AREA OF STRONG HEIGHT FALLS...ON THE ORDER OF 60-90M...WILL
OVERSPREAD THE OH VALLEY DURING THE DAY FRIDAY AS SLIGHTLY NEGATIVE
TILTED UPPER TROUGH AXIS PROGRESSES TO A POSITION FROM LOWER
MI...ARCING SEWD TO SC BY 02/00Z. AN EXPANSIVE AREA OF LARGE SCALE
ASCENT IS EXPECTED TO OVERSPREAD THE REGION AHEAD OF THIS UPPER
DIFFLUENT TROUGH AND SHOULD PROVE SUPPORTIVE OF WIDESPREAD
CONVECTION ALONG ADVANCING COLD FRONT AS IT SURGES EWD.

THUNDERSTORMS SHOULD BE ONGOING EARLY IN THE PERIOD ALONG THE COLD
FRONT FROM OH...SWD INTO NRN GA. WHILE STRONG SHEAR WILL COINCIDE
WITH THIS ACTIVITY IN ALL LIKELIHOOD BROKEN LINEAR TSTM SEGMENTS
SHOULD BE MOSTLY NON-SEVERE...OR PERHAPS MARGINALLY SEVERE AT
DAYBREAK. MAIN LIMITING FACTOR FOR SEVERE EARLY IN THE PERIOD WILL
BE DUE TO MEAGER INSTABILITY. HOWEVER...BOUNDARY LAYER HEATING
SHOULD AID IN AIR MASS DESTABILIZATION BY 18Z AND SUFFICIENT
BUOYANCY WILL DEVELOP FOR ROBUST UPDRAFTS WITHIN AN ENVIRONMENT MORE
THAN SUFFICIENTLY SHEARED FOR ORGANIZATION. IN FACT...FORECAST
SOUNDINGS SUGGEST ROTATING UPDRAFTS/SUPERCELL STRUCTURES ARE
POSSIBLE. GIVEN THE AFOREMENTIONED LARGE SCALE SUPPORT...IT APPEARS
A STRONGLY FORCED SQUALL LINE SHOULD BE NOTED WITH ADVANCING COLD
FRONT AND GRADUAL INTENSIFICATION IS EXPECTED AS AIR MASS
DESTABILIZES...PRIMARILY EAST OF THE APPALACHIANS AND WITH TIME
ACROSS PORTIONS OF PA. DAMAGING WINDS MAY BE COMMON WITH THE SQUALL
LINE...ESPECIALLY IF MUCAPE CAN EXCEED 1500 J/KG AS NAM SUGGESTS.
AT THIS TIME WILL MAINTAIN 30% SEVERE PROBS TO ACCOUNT FOR THE
EXPECTED STRONG WINDS WITH THE FRONTAL CONVECTION AND FOR ISOLATED
TORNADOES THAT COULD BE NOTED IF PRE-FRONTAL DISCRETE SUPERCELLS
DEVELOP. HOWEVER...THERE IS SOME CONCERN THAT A MORE WIDESPREAD
EVENT MAY EVOLVE IF LOW LEVEL LAPSE RATES/INSTABILITY RESPOND PRIOR
TO FRONTAL PASSAGE AND SEVERE PROBS MAY BE INCREASED TO ACCOUNT FOR
THIS SCENARIO IN LATER OUTLOOKS.

...TX PANHANDLE...

STRONG BOUNDARY LAYER HEATING IS EXPECTED BY MID DAY ACROSS THE HIGH
PLAINS FROM NERN NM INTO THE TX PANHANDLE. MODELS SUGGEST RAPID SFC
HEATING WILL CONTRIBUTE TO VERY STEEP LAPSE RATES ALONG BACK SIDE OF
SFC ANTICYCLONE AND AHEAD OF WEAK LEE CYCLONE. RESIDUAL LOW LEVEL
MOISTURE SHOULD PROVE ADEQUATE FOR THUNDERSTORM DEVELOPMENT AS
SBCAPE VALUES WILL LIKELY APPROACH 2000 J/KG ACROSS THE TX PANHANDLE
WHERE MID 50S DEW POINTS ARE ABLE TO BE MAINTAINED. WITH PRONOUNCED
DIRECTIONAL TURNING THROUGH A DEEP LAYER AND MID LEVEL FLOW ON THE
ORDER OF 30KT IT WOULD SEEM POSSIBLE THAT SCATTERED SUPERCELLS WILL
DEVELOP BY 21Z. SUBSEQUENT SSEWD PROPAGATION IS EXPECTED INTO THE
EARLY EVENING HOURS AIDED IN PART BY LLJ. LARGE HAIL IS THE MOST
LIKELY SEVERE THREAT.

...DAKOTAS...

HAVE OPTED TO LOWER THE SEVERE PROBS ACROSS PORTIONS OF THE DAKOTAS
FRIDAY AS LOW LEVEL MOISTURE/INSTABILITY ARE LIKELY FORECAST TOO
HIGH ACROSS THIS REGION IN LATEST MODEL GUIDANCE. THERE IS LITTLE
INDICATION...BASED ON LATEST OBSERVATIONAL DATA...THAT 50S SFC DEW
POINTS WILL RETURN TO THIS REGION AND BUOYANCY WILL THUS BE LESS
THAN FORECAST.

..DARROW.. 05/31/2012

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