DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 220457
SWODY1
SPC AC 220455

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1155 PM CDT THU JUN 21 2012

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE CNTRL AND
NRN HIGH PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE MID ATLANTIC REGION...

...SYNOPSIS...

OMEGA BLOCKING PATTERN IS IN PROCESS OF BECOMING ESTABLISHED AS AN
UPPER RIDGE BUILDS THROUGH THE SRN AND CNTRL PLAINS FLANKED BY A
TROUGH IN THE EAST AND WRN STATES. VORT MAX NOW OVER CA EMBEDDED
WITHIN LONGER WAVE TROUGH SHOULD REACH THE CNTRL/NRN HIGH PLAINS
LATER FRIDAY AFTERNOON. AT THE SFC A COLD FRONT WILL CONTINUE
THROUGH THE NERN U.S. AND MID ATLANTIC. SWRN PORTION OF THIS
BOUNDARY HAS STALLED OVER THE SRN PLAINS BUT WILL DEVELOP NWD
THROUGH THE CNTRL PLAINS AS LEE TROUGH STRENGTHENS.

...CNTRL AND NRN HIGH PLAINS...

A STRENGTHENING SLY LLJ ASSOCIATED WITH DEVELOPING LEE TROUGH WILL
TRANSPORT LOW 60S DEWPOINTS THROUGH THE CNTRL HIGH PLAINS BENEATH
PLUME OF 8-8.5 C/KM 700-500 MB LAPSE RATES. THIS PROCESS ALONG WITH
DIABATIC WARMING OF THE BOUNDARY LAYER SHOULD RESULT IN 2000-2500
J/KG MLCAPE DURING THE AFTERNOON. A CAPPING INVERSION WILL LIKELY
INHIBIT CONVECTIVE DEVELOPMENT MUCH OF THE DAY. HOWEVER...DEEPER
ASCENT ACCOMPANYING THE EJECTING SHORTWAVE TROUGH AND DIABATIC
WARMING SHOULD CONTRIBUTE TO STORM DEVELOPMENT INITIALLY OVER THE
HIGHER TERRAIN OF THE CNTRL ROCKIES AND BLACK HILLS OF SD THEN EWD
WITHIN THE WELL MIXED BOUNDARY LAYER OVER THE HIGH PLAINS. VERTICAL
SHEAR OF 40-45 KT WILL SUPPORT SUPERCELLS WITH LARGE HAIL THE MAIN
THREAT...BUT ISOLATED DAMAGING WIND AND A TORNADO OR TWO WILL ALSO
BE POSSIBLE. ACTIVITY WILL LIKELY EVENTUALLY CONSOLIDATE INTO AN MCS
SUPPORTED BY A STRENGTHENING NOCTURNAL LLJ WITH A CONTINUED THREAT
FOR ISOLATED LARGE HAIL AND DAMAGING WIND INTO MUCH OF THE EVENING.

...MID ATLANTIC AREA...

THE PRE-FRONTAL WARM SECTOR WILL ONCE AGAIN DESTABILIZE AS DIABATIC
WARMING COMMENCES FROM THE CAROLINAS INTO THE MID ATLANTIC. DESPITE
PRESENCE OF RICH LOW LEVEL MOISTURE...MLCAPE SHOULD REMAIN BELOW
1500 J/KG OWING TO WEAK MID LEVEL LAPSE RATES. A MODEST INCREASE IN
MID LEVEL FLOW WILL OCCUR AS THE UPPER TROUGH CONTINUES EWD...BUT
VERTICAL SHEAR WILL REMAIN WEAK AND SUPPORTIVE OF PULSE AND
MULTICELL STORM MODES. STORMS WILL LIKELY INCREASE IN COVERAGE IN
PRE-FRONTAL ZONE FROM THE CAROLINAS THROUGH THE MID ATLANTIC AND THE
NERN STATES BY LATE MORNING INTO THE AFTERNOON. STEEPENING LOW LEVEL
LAPSE RATES WILL SUPPORT ISOLATED STRONG WIND GUSTS WITH SOME
STORMS...BUT OVERALL THREAT APPEARS SOMEWHAT LIMITED BY THE MARGINAL
THERMODYNAMIC ENVIRONMENT AND WEAK VERTICAL SHEAR.

...MT...

A FEW STORMS MAY DEVELOP OVER THE HIGHER TERRAIN OF MT PROMOTED BY
DIABATIC WARMING/OROGRAPHIC FORCING AND INCREASINGLY DIVERGENT UPPER
FLOW EAST OF UPPER LOW CIRCULATION. A FEW OF THESE STORMS MAY
DEVELOP EWD WITH TIME WITHIN THE ELY UPSLOPE REGIME AND DEEPLY MIXED
BOUNDARY LAYERS ACROSS CNTRL MT. IT CURRENTLY APPEARS THE HIGHEST
CONCENTRATION OF STORMS WILL REMAIN OVER THE HIGHER TERRAIN WITH
COVERAGE FARTHER EAST LIMITED BY A CAPPING EML AND SHORTWAVE
RIDGING. STORMS THAT DEVELOP WILL HAVE POTENTIAL TO PRODUCE ISOLATED
STRONG WIND GUSTS AND HAIL.

..DIAL/HURLBUT.. 06/22/2012

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