DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 021936
SWODY1
SPC AC 021934

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0234 PM CDT MON SEP 02 2013

VALID 022000Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS NY/PA VICINITY...

HAVE MADE MINOR CHANGES TO 1630Z OUTLOOK...NAMELY TO SHIFT BACK EDGE
OF HIGHER SEVERE PROBS EAST ACROSS WESTERN NY. LATEST WV IMAGERY
CLEARLY DEPICTS SHORT-WAVE TROUGH PASSAGE AND RADAR DATA SUPPORTS
THIS WITH DEEP CONVECTION NOW APPROACHING 77W LONGITUDE. WHILE
THERE ARE TWO MAIN CLUSTERS OF SEVERE THAT HAVE DEVELOPED OVER
CURRENT WATCH...ERN LAKE ONTARIO AND OVER NWRN PA...A GRADUAL UPWARD
TREND IS EXPECTED WITH CONVECTION AHEAD OF SHORT-WAVE.

OTHERWISE...EARLIER THOUGHTS REGARDING CONVECTIVE EVOLUTION REMAIN
WITH MUCH OF TSTM ACTIVITY DIURNALLY DRIVEN ACROSS THE CONUS.

..DARROW.. 09/02/2013

.PREV DISCUSSION... /ISSUED 1130 AM CDT MON SEP 02 2013/

...SYNOPSIS...
A LARGE UPPER RIDGE IS FORECAST TO PERSIST ACROSS THE ROCKIES AND
ADJACENT PORTIONS OF THE PLAINS STATES THIS PERIOD...FLANKED BY TWO
TROUGHS -- ONE NEAR THE PAC COAST AND THE SECOND MOVING SLOWLY EWD
ACROSS THE GREAT LAKES/NORTHEAST. AT THE SURFACE...A COLD FRONT
WILL MOVE ACROSS THE PAC NW AHEAD OF THE WRN UPPER SYSTEM...WHILE A
SECOND FRONT CROSSES THE NORTHEAST/OH VALLEY REGION IN CONJUNCTION
WITH THE ADVANCE OF THE ERN UPPER TROUGH. THE ERN U.S. FRONT IN
PARTICULAR WILL FOCUS THE MAIN AREA OF SEVERE WEATHER RISK THIS
PERIOD.

...NY/PA VICINITY...
AS UPPER TROUGHING GRADUALLY INCREASES ACROSS THE REGION...WEAK
COOLING ALOFT AND SUSTAINED LARGE-SCALE ASCENT WILL REMAIN FAVORABLE
PRE-CONDITIONS FOR AN INCREASE IN CONVECTION THIS AFTERNOON. FAIRLY
WIDESPREAD CLOUDS WILL LIMIT HEATING TO SOME DEGREE ACROSS MOST OF
THE NORTHEAST...BUT RELATIVELY DIMINISHED CLOUD COVER FROM SRN NY
SWWD ACROSS PARTS OF PA SHOULD ALLOW MODERATE DESTABILIZATION OF THE
MOIST PRE-FRONTAL AIRMASS. AS SUCH...AN INCREASE IN STORMS
ALONG/AHEAD OF THE COLD FRONT IS EXPECTED THIS AFTERNOON.

FLOW ALOFT REMAINS MODEST...BUT AS THE UPPER LOW CENTERED OVER SRN
ONTARIO SLOWLY ADVANCES...SOME INCREASE IN WLY FLOW ALOFT IS
EXPECTED -- WHICH MAY AID IN POTENTIAL FOR STORMS TO LOCALLY
ORGANIZE. EVENTUALLY...A COUPLE OF STRONGER STORM CLUSTERS APPEAR
LIKELY TO EVOLVE...WITH ASSOCIATED/LOCALLY ENHANCED POTENTIAL FOR
MARGINALLY SEVERE WIND GUSTS. GIVEN THIS POTENTIAL...A SLIGHT
RISK/15% PROBABILITY WIND AREA IS BEING INTRODUCED FOR THIS
AFTERNOON AND EARLY EVENING. CONVECTION SHOULD DIMINISH INTO SUNSET
AND BEYOND IN CONJUNCTION WITH THE LOSS OF DIURNAL HEATING.

...MID OH/TN VALLEYS WSWWD INTO THE ARKLATEX REGION...
ONGOING CONVECTION ALONG A SLOWLY SAGGING COLD FRONT SHOULD INCREASE
IN COVERAGE WITH TIME...AS DIURNAL HEATING OF A MOIST PRE-FRONTAL
AIRMASS CONTINUES. WEAK SHEAR IS EVIDENT ACROSS THE AREA...WHICH
SHOULD LIMIT OVERALL ORGANIZATION/INTENSITY OF STORMS. LOCALLY
HOWEVER...A FEW STRONGER STORMS/STORM CLUSTERS CAPABLE OF PRODUCING
ISOLATED STRONGER WIND GUSTS WILL LIKELY OCCUR -- AND THUS A
BROAD/LOW-PROBABILITY RISK AREA REMAINS JUSTIFIED ACROSS THIS
REGION.

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