DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 110602
SWODY1
SPC AC 110600

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT WED SEP 11 2013

VALID 111200Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE GREAT LAKES
REGION/NORTHEAST STATES/NORTHERN NEW ENGLAND...

...SYNOPSIS...
A BLOCKING PATTERN WILL PERSIST OVER THE EASTERN PACIFIC INTO THE
WESTERN STATES...WHILE CONSIDERABLE TROUGH AMPLIFICATION OCCURS OVER
SOUTHEAST CANADA AND THE GREAT LAKES THROUGH EARLY THURSDAY.

...NORTHEAST STATES/NEW ENGLAND/LOWER GREAT LAKES...
AHEAD OF THE PRIMARY AMPLIFYING UPPER TROUGH OVER THE GREAT LAKES
REGION...GRADUAL HEIGHT FALLS WILL OVERSPREAD THE MAJORITY OF THE
LOWER LAKES/NORTHEAST STATES AND NEW ENGLAND ESPECIALLY INTO THIS
AFTERNOON AND MORE SO TONIGHT. WIDELY SCATTERED TSTMS ARE LIKELY TO
BE ONGOING EARLY TODAY ESPECIALLY NORTH OF THE INTERNATIONAL
BORDER...BUT POTENTIALLY ALSO INTO PARTS OF NORTHERN NEW ENGLAND AND
NEAR LAKE MI/ACROSS LOWER MI. A PERSISTENT/STRONG WESTERLY FEED OF
MOIST/POTENTIALLY UNSTABLE AIR WILL OTHERWISE CONTINUE TO SPREAD
INTO THE REGION AHEAD OF A SLOW SOUTHEASTWARD MOVING COLD FRONT. AN
INTENSIFICATION OF SURFACE BASED STORMS ARE LIKELY TO OCCUR
ALONG/SOUTHEAST OF THE COLD FRONT /AND PERHAPS NEAR A NORTHEAST
STATES SURFACE TROUGH/ THIS AFTERNOON AND EARLY EVENING...INITIALLY
ACROSS SOUTHERN ONTARIO/QUEBEC AND A NEAR-BORDER CORRIDOR FROM
SOUTHERN LOWER MI TO THE LOWER GREAT LAKES AND NORTHERN NEW ENGLAND.


AHEAD OF THE FRONT...STRONG HEATING...A PLUME OF RELATIVELY STEEP
MID-LEVEL LAPSE RATES...AND THE GENERAL PREVALENCE OF AT LEAST
MIDDLE/UPPER 60S F SURFACE DEWPOINTS WILL LIKELY SUPPORT A BROAD
CORRIDOR OF MODERATE/STRONG DESTABILIZATION WITH AS MUCH AS
2000-3500 J/KG MLCAPE. AS STORMS INTENSIFY WITHIN THE UNSTABLE
AIRMASS...MODERATELY STRONG DEEP LAYER WESTERLIES NEAR/JUST SOUTH OF
THE FRONT MAY AT LEAST INITIALLY SUPPORT SPLITTING SUPERCELLS
ESPECIALLY ACROSS FAR NORTHERN PORTIONS OF NY AND NORTHERN NEW
ENGLAND. THIS WILL BE ASIDE FROM A PREVALENT/PROBABLE EVOLUTION OF
MULTICELLS/LINE SEGMENTS...WITH DAMAGING WINDS/SOME SEVERE HAIL
CONTINUING/SPREADING SOUTHEASTWARD THROUGH THIS EVENING.

...UPPER GREAT LAKES...
RELATIVELY LOW-TOPPED TSTMS MAY DEVELOP/INTENSIFY ALONG A SECONDARY
COLD FRONT IN THE PRESENCE OF AMPLE DPVA IN ASSOCIATION WITH THE
AMPLIFYING UPPER TROUGH. SUCH DEVELOPMENT POTENTIALLY INCLUDES UPPER
MI/NORTHERN LOWER MI AND PERHAPS PARTS OF WI. THE BOUNDARY LAYER
WILL NOT BE PARTICULARLY MOIST OR UNSTABLE IN THE WAKE OF THE
PRIOR/INITIAL COLD FRONT...BUT STEEPENING LOW-LEVEL LAPSE
RATES/STRONG DEEP LAYER WESTERLIES MAY ALLOW FOR SOME STRONGER
LOW-TOPPED STORMS AND POTENTIAL CLUSTERS CAPABLE OF LOCALLY DAMAGING
WINDS AND ISOLATED HAIL DURING THE AFTERNOON/EARLY EVENING HOURS.

...MIDDLE-LOWER MO VALLEY TO CENTRAL HIGH PLAINS...
SCATTERED TSTMS WILL PERSIST/DIURNALLY RE-INTENSIFY THIS AFTERNOON
ALONG A SOUTHWARD SAGGING COLD FRONT. A TENDENCY FOR WEAK HEIGHT
RISES/SLIGHT WARMING ALOFT AND WEAK VERTICAL SHEAR WILL ACCOMPANY
THE MAJORITY OF THE FRONTAL ZONE /SOUTHWEST OF THE MIDWEST REGION/.
NONETHELESS...SUFFICIENT HEATING/DESTABILIZATION WILL ALLOW FOR A
FEW STRONGER STORMS CAPABLE OF DOWNBURSTS.

..GUYER/COHEN.. 09/11/2013

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