SWODY1
SPC AC 122000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT SUN JUN 12 2011
VALID 122000Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID-ATLANTIC
STATES/CAROLINAS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF KS AND THE
ADJACENT LOWER MO VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTH-CENTRAL HIGH
PLAINS...
...MID-ATLANTIC STATES/DELMARVA/CAROLINAS...
FEW CHANGES...SEE PRIOR DISCUSSION AS BELOW AND SUBSEQUENT MESOSCALE
DISCUSSIONS INCLUDING SPC MD 1195.
...KS AND THE ADJACENT MO VALLEY...
THE LIKELIHOOD/EXTENT OF SURFACE BASED DEEP CONVECTIVE DEVELOPMENT
STILL REMAINS QUESTIONABLE THIS AFTERNOON/EARLY EVENING IN VICINITY
OF MULTIPLE NORTHWARD RETURNING WEAK OUTFLOW BOUNDARIES ACROSS
OK/SOUTHERN KS AND/OR THE FRONTAL ZONE THAT A RESIDES A BIT FARTHER
NORTH ACROSS KS. AS PREVIOUSLY DISCUSSED...THE MORE CERTAIN SCENARIO
IS FOR TSTMS WITH A RISK OF SEVERE TO INCREASE LATER TONIGHT.
...NORTHERN-CENTRAL HIGH PLAINS...
ONE CHANGE AT 20Z WAS TO EXTEND THE SLIGHT RISK SOUTHWARD INTO
NORTHERN CO...WHERE CONCERN FOR AT LEAST ISOLATED SEVERE TSTMS
EXISTS ACROSS THE CENTRAL HIGH PLAINS INCLUDING A FEW SUPERCELLS.
THIS IS GENERALLY ATTRIBUTABLE TO A RELATIVELY MOIST HIGH PLAINS AIR
MASS/WEAK UPSLOPE AND A SPEED MAX CROSSING CO AS NOTED IN SATELLITE
IMAGERY/DERIVED WIND DATA. OTHERWISE...SEE PRIOR REASONING BELOW AND
TORNADO WATCH 468.
..GUYER.. 06/12/2011
.PREV DISCUSSION... /ISSUED 1130 AM CDT SUN JUN 12 2011/
...KS/OK/MO/AR THIS AFTERNOON INTO TONIGHT...
A COMPLICATED FORECAST SCENARIO CENTERED ON KS THIS
AFTERNOON/EVENING. AN INITIAL OUTFLOW BOUNDARY EXTENDS FROM CENTRAL
AR WWD INTO SRN/CENTRAL OK...WHILE A REINFORCING OUTFLOW IS SLOWING
ITS SWD/SWWD MOTION ACROSS SRN KS/NRN OK. THE SYNOPTIC FRONT IS
LOCATED FARTHER TO THE N ACROSS SRN MO AND NE KS. THE SRN OUTFLOW
BOUNDARY WILL LIKELY LOSE DEFINITION AND DRIFT NWD THIS
AFTERNOON...WHILE THE REINFORCING OUTFLOW STALLS ACROSS CENTRAL
KS/NRN OK AS THE DRIVING CONVECTION DIMINISHES IN CONJUNCTION WITH
WEAKENING LOW-LEVEL WAA...AND AS THE REMNANT MCV MOVES EWD OVER MO.
A WEAK MIDLEVEL VORTICITY MAXIMUM OVER ERN CO WILL MOVE EWD/NEWD
OVER KS/NEB...BUT GENERAL HEIGHT RISES ARE EXPECTED OVER THE
SRN/CENTRAL PLAINS. THE RISING HEIGHTS AND SWWD DISPLACEMENT OF THE
MORNING OUTFLOW BOUNDARIES FROM THE SYNOPTIC FRONT...AND BENEATH AN
INCREASINGLY WARM EML...ALL INTRODUCE UNCERTAINTY REGARDING NEW
STORM FORMATION IN KS THIS AFTERNOON. IF STORMS WERE TO
FORM...SUPERCELLS WOULD BE LIKELY WITH A RISK OF LARGE HAIL AND
PERHAPS TORNADOES...THUS WILL MAINTAIN A HIGHLY CONDITIONAL SLIGHT
RISK AREA FOR THIS AFTERNOON/EVENING. A GREATER RISK FOR STORMS
WITH LARGE HAIL IS EXPECTED TONIGHT AS THE RESIDUAL OUTFLOWS AND
SYNOPTIC FRONT CONSOLIDATE ACROSS KS...AND LOW-LEVEL WAA INCREASES
WITH THE NOCTURNAL LLJ. MUCAPE AOA 2000 J/KG AND EFFECTIVE BULK
SHEAR IN EXCESS OF 40 KT COULD SUPPORT ELEVATED SUPERCELLS CAPABLE
OF PRODUCING LARGE HAIL...AS WELL AS ISOLATED DAMAGING WINDS GIVEN
THE RELATIVELY STEEP MIDLEVEL LAPSE RATES AND DCAPE IN EXCESS OF
1000 J/KG.
...WRN SD AND VICINITY THIS AFTERNOON INTO EARLY TONIGHT...
A MIDLEVEL SHORTWAVE TROUGH OVER ERN ID WILL EJECT ENEWD TO THE NRN
HIGH PLAINS BY THIS EVENING...AND HELP MAINTAIN AN INVERTED TROUGH
ACROSS ERN WY/SE MT. E OF THE TROUGH...BOUNDARY LAYER DEWPOINTS OF
55-60 F AND SURFACE HEATING IN CLOUD BREAKS WILL ALLOW MLCAPE TO
INCREASE TO 1500-2500 J/KG AND CONVECTIVE INHIBITION TO WEAKEN. THE
MODERATE INSTABILITY WILL BE COMPLEMENTED BY WIND PROFILES WITH
SUFFICIENT BULK SHEAR AND HODOGRAPH CURVATURE TO PROMOTE SUPERCELL
DEVELOPMENT.
EXPECT INITIAL CONVECTIVE DEVELOPMENT BY MID AFTERNOON ACROSS NE WY
AND SE MT...WITH CONVECTION SUBSEQUENTLY SPREADING NEWD ACROSS WRN
SD AND SW ND. THE INITIAL STORMS WILL BE MORE DISCRETE AND CAPABLE
OF PRODUCING LARGE HAIL AND A COUPLE OF TORNADOES. UPSCALE GROWTH
INTO A CLUSTER/MCS IS EXPECTED THIS EVENING...WITH THE SEVERE
THREATS SHIFTING TO PRIMARILY DAMAGING WINDS AND HAIL.
...ERN PA SWD TO NC THIS AFTERNOON...
A SURFACE COLD FRONT IS MOVING SEWD INTO CENTRAL PA AND NRN
WV/KY...WHILE A BACKDOOR FRONT HAS STALLED ACROSS SRN NJ AND ERN PA.
THE COLD FRONT IS ASSOCIATED WITH A MIDLEVEL TROUGH MOVING EWD
TOWARD THE SAINT LAWRENCE VALLEY...WITH A SWD EXTENDING LOBE TOWARD
WRN PA. AN ACCOMPANYING BELT OF 30-50 KT WLY FLOW IN THE 500-300 MB
LAYER WILL EXTEND AS FAR S AS NRN VA/MD/PA THIS AFTERNOON IN THE
PRE-FRONTAL WARM SECTOR.
INITIAL CONVECTIVE DEVELOPMENT IS OCCURRING ALONG THE COLD FRONT
ACROSS SW/CENTRAL/NE PA...AND SOME INTENSIFICATION OF THIS
CONVECTION IS EXPECTED THIS AFTERNOON AS IT ENCOUNTERS A REGION OF
STRONGER SURFACE HEATING AND RICHER BOUNDARY LAYER MOISTURE W OF THE
BACKDOOR FRONT. LAPSE RATE PROFILES WILL NOT BE PARTICULARLY STEEP
AND ARE SUGGESTIVE OF ONLY A MARGINAL HAIL THREAT...BUT EFFECTIVE
BULK SHEAR OF 30-40 KT WILL SUPPORT A FEW ORGANIZED STORMS CAPABLE
OF PRODUCING AT LEAST ISOLATED DAMAGING WINDS THIS AFTERNOON.
DEEP-LAYER FLOW AND VERTICAL WEAKEN BOTH WEAKEN WITH SWD EXTENT
ACROSS VA/NC. HERE...THE ENVIRONMENT WITH MLCAPE OF 1500-2000 J/KG
AND STEEP LOW-LEVEL LAPSE RATES WILL BE CONDUCIVE TO THE FORMATION
OF MULTICELL CLUSTERS CAPABLE OF PRODUCING A FEW DAMAGING DOWNBURSTS
AND SOME HAIL.
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