DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 141254
SWODY1
SPC AC 141253

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0753 AM CDT TUE AUG 14 2012

VALID 141300Z - 151200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MIDDLE ATLANTIC REGION
INTO THE SERN US...

...SYNOPSIS...
AN UPPER LEVEL LONG WAVE TROUGH IS FORECAST TO CONTINUE OVER THE ERN
US AS A SERIES OF SHORT WAVE TROUGHS ROTATE THROUGH THE MEAN TROUGH
POSITION...WHILE A VIGOROUS UPSTREAM VORTICITY MAX/TROUGH EVIDENT IN
WATER VAPOR IMAGERY OVER CENTRAL BC IS EXPECTED TO DIG SEWD TOWARD
THE SRN CANADIAN PRAIRIE PROVINCES/NRN MT BY THE END OF THE PERIOD.
THE SWRN US UPPER RIDGE IS FORECAST TO PERSIST THROUGH TONIGHT.

AT THE SURFACE...A WEAK COLD FRONT EXTENDS FROM LAKE ERIE SWWD
ACROSS THE TN VALLEY THEN WWD ACROSS NRN TX. THE NRN PART OF THE
FRONT IS EXPECTED TO MOVE EWD INTO THE MIDDLE ATLANTIC STATES AND
CENTRAL/SRN APPALACHIANS...WHILE THE WRN PORTION OF THE FRONT LIFTS
SLOWLY NWD OVER THE SRN PLAINS TONIGHT. A STRONGER CANADIAN COLD
FRONT IS FORECAST TO SURGE SEWD REACHING THE NRN MT BORDER THIS
EVENING CONTINUING TO A NERN ND/NWRN SD/NRN WY LINE BY 15/12Z.

...MIDDLE ATLANTIC STATES INTO THE CAROLINAS AND GA...
SCATTERED MORNING CONVECTION IS OCCURRING OVER THE MIDDLE ATLANTIC
REGION IN ASSOCIATION WITH A SHORT WAVE TROUGH LIFTING NEWD FROM
CENTRAL NY INTO NRN VA. THIS ACTIVITY IS EXPECTED TO CONTINUE NEWD
THIS MORNING WITH VISIBLE IMAGERY SHOWING A DECREASE IN CLOUD COVER
FROM SERN OH/WRN PA INTO WV IN THE WAKE OF THIS INITIAL CONVECTION.
THIS WILL PERMIT STRONGER DIABATIC HEATING AND DESTABILIZATION TO
SPREAD EWD THIS AFTERNOON...AND WHEN COUPLED WITH SURFACE DEW POINTS
GENERALLY IN THE 60S...WILL RESULT IN AN UNSTABLE ENVIRONMENT WITH
MLCAPE REACHING 1000-1500 J/KG.

ADDITIONAL STORMS ARE EXPECTED TO DEVELOP BY THIS AFTERNOON FROM
PARTS OF ERN OH/PA/NRN MD SWWD INTO WV AND NRN/WRN VA AS LARGE SCALE
ASCENT IN ADVANCE OF AN UPSTREAM SHORT WAVE TROUGH APPROACHING THE
AREA FROM THE WEST OVERSPREADS THE COLD FRONT. WSWLY MID LEVEL FLOW
OF 25-30 KT WILL CONTRIBUTE TO SUFFICIENT DEEP LAYER SHEAR TO
PROMOTE MAINLY ORGANIZED MULTICELL STORMS CAPABLE OF PRODUCING
STRONG/SEVERE WIND GUSTS AND HAIL AS THEY SPREAD EWD THROUGH THE
EVENING HOURS. THERE IS ALSO A THREAT FOR ISOLATED SUPERCELLS AND
ATTENDANT BRIEF TORNADO POTENTIAL OVER THE DELMARVA REGION WHERE
SELY LOW LEVEL WINDS WILL ENHANCE VERTICAL SHEAR.

FARTHER SOUTH...MORNING CONVECTION FROM ERN TN/EXTREME WRN NC INTO
ERN AL/WRN GA IS AHEAD OF A STRONGER SHORT WAVE TROUGH MOVING INTO
THE SERN STATES. THE NRN PART OF THE ACTIVITY HAS BEEN STEADILY
WEAKENING OVER THE LAST FEW HOURS BUT STORMS ARE PERSISTING IN A N/S
AXIS ENTERING WRN GA. WIDELY SCATTERED CONVECTION IS EXPECTED TO
INCREASE AGAIN THIS AFTERNOON AS SUSTAINED LARGE SCALE ASCENT
COUPLED WITH ZONES OF DIABATIC HEATING DIMINISH CIN. MID LEVEL 30
KT WESTERLY WINDS AND 20-30 KT DEEP LAYER SHEAR WILL SUPPORT
MULTICELL STORM STRUCTURES WITH A THREAT FOR STRONG DOWNBURST WINDS
AND ISOLATED HAIL TO OCCUR. ACTIVITY SHOULD SPREAD EWD INTO THE
EVENING BEFORE WEAKENING AFTER SUNSET AS BOUNDARY LAYER
COOLING/STABILIZATION OCCURS.

...NERN NM/TX PANHANDLE REGION ESEWD ACROSS SWRN OK/N TX...
AFTERNOON CONVECTIVE DEVELOPMENT IS FORECAST ALONG THE
QUASI-STATIONARY FRONT EXTENDING ACROSS THIS AREA...AS DIURNAL
HEATING RESULTS IN MODEST DESTABILIZATION ATOP A DEEP MIXED LAYER.
WHILE STRONGER FLOW ALOFT SHOULD REMAIN N OF THE RED RIVER ON THE
COOL SIDE OF THE BOUNDARY...A FEW MULTICELL CLUSTERS WILL BE
POSSIBLE. THIS -- COMBINED WITH THE DEEP SUB-CLOUD LAYER ENHANCING
DOWNDRAFT POTENTIAL AND STEEP LAPSE RATES -- SUGGESTS
LOW-PROBABILITY THREAT FOR ISOLATED DAMAGING GUSTS AND HAIL INTO THE
EVENING HOURS.

..WEISS/GARNER.. 08/14/2012

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