Thursday, May 19, 2011

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 191733
SWODY2
SPC AC 191731

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT THU MAY 19 2011

VALID 201200Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE PLAINS...

...SYNOPSIS...
LARGE SCALE DEEP-LAYER CYCLONE SITUATED ACROSS THE WRN STATES WILL
MAKE ITS MOVE EAST THIS PERIOD AS A STRONG SHORT WAVE TROUGH...NOW
EVIDENT IN WV IMAGERY ACROSS THE LOWER COLORADO RIVER VALLEY...
PIVOTS THROUGH THE BASE OF THE LARGER TROUGH TODAY AND EMERGES OVER
THE SRN AND CNTRL HIGH PLAINS ON FRIDAY. DIFFLUENT/DIVERGENT MID AND
UPPER LEVEL FLOW AND MODEST DIURNAL DESTABILIZATION WELL AHEAD OF
THE STRONGER SHORT WAVE TROUGH WILL LIKELY AID TSTM DEVELOPMENT
ACROSS PARTS OF OK/KS TODAY AND TONIGHT. THE EVOLUTION OF THIS
CONVECTION INTO EARLY FRIDAY WILL IMPACT SEVERE WEATHER POTENTIAL
AND STORM MODE DURING THE DAY 2 PERIOD.

CUT-OFF LOW IN THE NORTHEAST WILL CONTRIBUTE TO ONE MORE DAY OF
DIABATICALLY-DRIVEN LOW-TOPPED TSTMS WITH MARGINAL SEVERE WEATHER
POTENTIAL ON FRIDAY BEFORE LARGE SCALE PATTERN CHANGES ACT TO SHUNT
THE UPPER LOW EWD INTO THE ATLANTIC.

...GREAT PLAINS...
A COUPLE OF CONVECTIVE COMPLEXES ARE EXPECTED TO BE UNDERWAY OVER
THE PLAINS BY FRIDAY MORNING DRIVEN BY WARM ADVECTION AND LIFT
WITHIN EXTENSIVE WARM CONVEYOR BELT AHEAD OF THE DEEP-LAYER UPPER
TROUGH FROM TX TO NEB. CONSENSUS ACROSS A VARIETY OF MODEL GUIDANCE
SUGGESTS THAT ONE AREA OF GREATER MORNING STORM POTENTIAL WILL
EXTEND FROM TX INTO CNTRL/ERN OK...AND ANOTHER MCS MAY BE SITUATED
FARTHER NORTH...ACROSS THE MIDDLE MISSOURI RIVER VALLEY. IT IS
POSSIBLE THAT THIS CONVECTION WILL BE MAINTAINED ACROSS AR/MO/IA AND
TOWARD THE MS RIVER VALLEY THROUGH THE DAY AS HEIGHT FALLS WITH THE
APPROACHING LARGE SCALE TROUGH AND MOISTURE TRANSPORT ACT TO
MAINTAIN A FAVORABLE DAYTIME REGIME FOR CONVECTION.

EXPECT THERE WILL BE SOME AIR MASS RECOVERY IN THE WAKE OF THE
MORNING STORMS...FROM TX TO KS...WHERE DIURNAL HEATING AMIDST MODEST
LOW LEVEL MOISTURE WILL CONTRIBUTE TO MLCAPE VALUES CLIMBING INTO
THE RANGE OF 1000 J PER KG NORTH TO AS HIGH AS 2000 J PER KG SOUTH.
COMBINATION OF SHORT WAVE/FRONTAL AND DRYLINE FORCING SPREADING EAST
ACROSS THE DESTABILIZING AIR MASS...ALONG WITH DEEP-LAYER AND
SOMEWHAT UNIDIRECTIONAL SHEAR...SHOULD PROMOTE THE DEVELOPMENT OF
FAIRLY WIDESPREAD ORGANIZED STORMS. RESIDUAL OUTFLOW AND
DIFFERENTIAL HEATING BOUNDARIES LEFT IN THE WAKE OF MORNING MCS
ACTIVITY COULD LOCALLY ENHANCE LOW LEVEL SHEAR TO SUPPORT SOME
TORNADO POTENTIAL WITHIN THE HIGHER PROBABILITY AREA DEPICTED ON THE
OUTLOOK. HOWEVER...MERIDIONAL COMPONENT OF THE DEEP-LAYER FLOW
SUGGESTS FAST-MOVING CLUSTERS AND LINES OF STORMS POSING A THREAT OF
BOTH HIGH WINDS AND LARGE HAIL.

ANOTHER MCS OR TWO SHOULD EVOLVE THROUGH THE LATE EVENING FROM AR
ACROSS MO AND AS FAR NORTH AS NEB/IA. THIS ACTIVITY WILL LIKELY
BECOME FURTHER REMOVED FROM SURFACE-BASED INSTABILITY WITH TIME BUT
COULD STILL POSE SOME CHANCE FOR HAIL WITHIN THE ERN ARC OF THE
LOWER PROBABILITY AREA THROUGH SATURDAY MORNING.

...NORTHEAST...
COLD CORE LOW AND AMBIENT VORTICITY WILL AGAIN SUPPORT A DIURNAL
INCREASE IN SCATTERED TSTMS IN THE NORTHEAST. SOME HAIL AND PERHAPS
A STRONG GUST OR TWO CANNOT BE RULED OUT IN THIS ENVIRONMENT.

..CARBIN.. 05/19/2011

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