SWODY1
SPC AC 201613
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1113 AM CDT SUN JUN 20 2010
VALID 201630Z - 211200Z
...THERE IS A MDT RISK OF SVR TSTMS FROM NERN WY/SERN MT ACROSS SRN
AND WRN SD/MUCH OF NEB INTO WRN IA/FAR NRN MO...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...FROM THE NRN AND CNTRL HI PLNS TO THE MID MS VLY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF NEW ENGLAND AND
THE MID ATLANTIC CST...
...SYNOPSIS...
UPPER LOW OVER OREGON TO MOVE TO SWRN MT BY 12Z MON. OF MORE
IMPORTANCE TO SEVERE DEVELOPMENT TODAY IS THE MID LEVEL TROUGH/WIND
MAX ROTATING NEWD FROM UT/NV ACROSS CO/WY THIS AFTERNOON THEN EWD
INTO PLAINS TONIGHT. OUTFLOW FROM OVERNIGHT CONVECTION HAS PUSHED
LOW LEVEL MOISTURE WWD TO FRONT RANGE NRN CO AND AS FAR W AS E
SLOPES OF WIND RIVER AND BIG HORN MTNS IN WY.
SFC LOW WRN KS WILL DEEPEN THIS AFTERNOON SUPPORTING THE VERY
MOIST/UNSTABLE BOUNDARY LAYER IN CENTRAL PLAINS TO DEVELOP NWD INTO
SRN NEB.
...NRN/CENTRAL HIGH PLAINS...
MDT RISK HAS BEEN EXTENDED WWD TO E SLOPES OF NERN WY INTO SERN MT
AS THE MOIST UPSLOPE EXPECTED TO HOLD UNTIL STORM INITIATION BY MID
AFTERNOON. WITH MLCAPES AOA 2000 J/KG...40-50KT OF SHEAR AND VERY
STEEP MID LEVEL LAPSE RATES...CONDITIONS SUPPORT SUPERCELLS AND VERY
LARGE HAIL. IN ADDITION TORNADOES WILL BE POSSIBLE WITH ANY
SUPERCELL.
HAVE EXTENDED THE SLIGHT SWD TO DEN METRO GIVEN THE CURRENT
AVAILABLE LOW LEVEL MOISTURE AND POTENTIAL OF THE CAP ERODING. IF
CONVECTION IS ABLE TO INITIATE THE AMOUNT OF CAPE AND SHEAR WILL
SUPPORT SUPERCELLS INCLUDING LARGE HAIL.
SEVERE THUNDERSTORMS WILL MOVE/PROPAGATE EWD INTO NRN HIGH PLAINS BY
THIS EVENING...LIKELY DEVELOPING UPSCALE INTO ONE OR MORE MCS/S
ACCOMPANIED BY DAMAGING WINDS ALONG WITH THE LARGE HAIL AND ISOLATED
TORNADO POTENTIAL.
...SD/NEB/WRN IA...
BY LATER THIS AFTERNOON/EVENING SEVERE THUNDERSTORM DEVELOPMENT WILL
RESPOND TO THE VERY UNSTABLE WARM SECTOR SURGING NWD THRU CENTRAL
PLAINS WITH MLCAPES AOA 4000 J/KG BY MID AFTERNOON AND BEING LIFTED
BY RETREATING E/W SURFACE BOUNDARY VICINITY KS/NEB BORDER. VEERING
SHEAR PROFILES COUPLED WITH THE HIGH INSTABILITY...SUPPORT
SUPERCELLS INCLUDING TORNADO AND VERY LARGE HAIL THREAT. AGAIN SOON
AFTER INITIATION STORMS WILL DEVELOP UPSCALE TO FORWARD PROPAGATING
MCS/S AND AN INCREASING CONCERN FOR DAMAGING WINDS. OVERNIGHT THERE
IS CERTAINLY A POTENTIAL FOR A DERECHO TYPE WIND EVENT TRACKING FROM
NEB INTO IA...WITH DETAILS YET TO BE DETERMINED.
HAVE SHIFTED MDT RISK S AND W OUT OF PORTIONS OF SD AND IA GIVEN
THAT THE FOCUS OF CONVERGENCE WITH THE LOW LEVEL JET THIS EVENING IS
ACROSS NEB INTO WRN IA.
...NEW ENGLAND AND SERN NY/NJ TODAY...
COLD FRONT EXTENDS FROM WRN NY INTO SERN QUEBEC WITH A PRE-FRONTAL
TROUGH FROM SERN NY NEWD INTO THE NEW ENGLAND STATES. DIABATIC
WARMING OF THE MOIST BOUNDARY LAYER IS DESTABILIZING THE WARM
SECTOR...BUT MLCAPE SHOULD REMAIN BELOW 2000 J/KG DUE TO MODEST /6
C/KM 700-500 MB/ LAPSE RATES. WEAK CAP AND DEEPER FORCING FOR ASCENT
ASSOCIATED VORTICITY MAXIMUM MOVING THROUGH SRN QUEBEC IS
CONTRIBUTING TO THE DEVELOPMENT OF STORMS ACROSS NRN ME AS WELL AS
FARTHER SOUTHWEST ALONG THE FRONT AND IN PRE-FRONTAL WARM SECTOR. A
BELT OF 35-40 KT FLOW ALOFT ALONG SRN PERIPHERY OF UPPER TROUGH IS
CONTRIBUTING TO 30-35 KT UNIDIRECTIONAL WLY BULK SHEAR. THIS
ENVIRONMENT WILL SUPPORT MIXED CONVECTIVE MODES WITH MULTICELL LINE
SEGMENTS...A FEW SMALL CLUSTERS AS WELL AS SOME DISCRETE CELLS WITH
MODEST UPDRAFT ROTATION.
..HALES/STOPPKOTTE.. 06/20/2010
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