DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 211729
SWODY2
SPC AC 211728

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT THU JUN 21 2012

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF WRN SD/WRN
NEB AND VICINITY...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE
MID-ATLANTIC REGION...

...SYNOPSIS...
LARGE-SCALE RIDGING IS FORECAST TO PERSIST ACROSS THE CENTRAL U.S.
THIS PERIOD...WITH SOME EWD PROGRESSION OF THE OVERALL PATTERN AS A
STRONG NERN PACIFIC UPPER LOW CONTINUES DIGGING SLOWLY SEWD TOWARD
THE W COAST AND A SECOND TROUGH ADVANCES FROM THE UPPER GREAT LAKES
REGION INTO THE NORTHEAST U.S. THROUGH THE END OF THE PERIOD.

AT THE SURFACE...A COLD FRONT ACCOMPANYING THE NERN U.S. TROUGH IS
FORECAST TO LIE FROM NRN NEW ENGLAND SWWD ACROSS THE MID-ATLANTIC
REGION DURING THE AFTERNOON -- FOCUSING A ZONE OF CONVECTION ACROSS
THIS AREA. FARTHER W...A SURFACE TROUGH EXTENDING ESEWD ACROSS MT
AND THEN SWD ALONG THE NRN/CENTRAL HIGH PLAINS AREA SHOULD ALSO
PROVIDE SOME FOCUS FOR STORM INITIATION DURING THE AFTERNOON.

...WRN SD/WRN NEB AND VICINITY...
DESPITE PERSISTENT BACKGROUND RIDGING...MODELS CONTINUE TO SUGGEST
THAT A WEAK SHORT-WAVE TROUGH WILL EJECT NEWD ACROSS THE WY VICINITY
DURING THE DAY AND THEN ACROSS THE HIGH PLAINS INTO THE SD/NEB
REGION BY EVENING...WITHIN SWLY FLOW ALOFT AHEAD OF THE LARGE NERN
PACIFIC UPPER LOW.

EJECTION OF THIS FEATURE ATOP A STRENGTHENING LEE TROUGH SUGGEST
DEVELOPMENT OF ISOLATED AFTERNOON CONVECTION...WITH INCREASED STORM
COVERAGE/UPSCALE GROWTH LIKELY INTO THE EVENING AS A STRONG SLY/SELY
LOW-LEVEL JET DEVELOPS IN RESPONSE TO THE PASSING SHORT-WAVE
FEATURE.

WITH A MODEST INCREASE IN MID-LEVEL WLYS/SWLYS -- SPREADING ATOP THE
INCREASING LOW-LEVEL FLOW...SHEAR WILL BECOME SUPPORTIVE OF
ORGANIZED/SUPERCELL STORMS. THUS -- EXPECT POTENTIAL FOR LOCALLY
DAMAGING WINDS AND LARGE HAIL TO ACCOMPANY THE STRONGER STORMS.

...PORTIONS OF THE MID-ATLANTIC REGION...
AS HEIGHT FALLS OVERSPREAD THE MID-ATLANTIC REGION AHEAD OF THE
ADVANCING UPPER TROUGH...STORM DEVELOPMENT IS FORECAST NEAR/AHEAD OF
THE SURFACE COLD FRONT -- WHICH SHOULD BE LOCATED E OF THE MOUNTAINS
BY MIDDAY/EARLY AFTERNOON. HEATING/DESTABILIZATION OF THE
ENVIRONMENT SUGGEST POTENTIAL FOR A FEW STRONGER CELLS...THOUGH
MODEST SHEAR MAY LIMIT OVERALL SEVERE THREAT. STILL...WITH
CAPE/SHEAR COMBINATION LIKELY TO SUPPORT AT LEAST LOCAL
ORGANIZATION...EXPECT GUSTY WINDS AND POTENTIAL FOR ISOLATED WIND
DAMAGE WITH STRONGER CELLS/STORM CLUSTERS THROUGH EARLY EVENING.
WHILE LIMITED THREAT MAY EXTEND AS FAR N AS NRN NEW
ENGLAND...GREATEST POTENTIAL APPEARS TO EXIST WITHIN THE NEW YORK
CITY/PHILADELPHIA/WASHINGTON D.C. CORRIDOR FROM MID AFTERNOON TO
EARLY EVENING.

...NRN INTERMOUNTAIN REGION...
AS SHORT-WAVE RIDGING SHIFTS EWD WITH CONTINUED SEWD ADVANCE OF THE
PACIFIC UPPER LOW TOWARD THE PAC NW...A STRONGER/DIFFLUENT MID- AND
UPPER-LEVEL FLOW FIELD WILL OVERSPREAD ERN PORTIONS OF THE PAC NW
AND INTO THE NRN INTERMOUNTAIN REGION.

WITH DAYTIME HEATING/MIXING...EVENTUAL EVOLUTION OF A FAIRLY DEEP
MIXED LAYER BENEATH AMPLE MID-LEVEL CAPE SUGGEST THAT ISOLATED
SEVERE STORMS COULD EVOLVE FROM WITHIN THE ZONE OF SCATTERED
CONVECTIVE DEVELOPMENT...AIDED BY THE FAVORABLY SHEARED ENVIRONMENT.
THEREFORE...WILL MAINTAIN 5% SEVERE THREAT AREA FOR ISOLATED
WIND/HAIL POTENTIAL...THOUGH QUESTIONS REGARDING COVERAGE OF
STRONGER CONVECTION PRECLUDE ANY UPGRADE TO HIGHER SEVERE
PROBABILITY ATTM.

..GOSS.. 06/21/2012

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