SWODY2
SPC AC 121731
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT MON SEP 12 2011
VALID 131200Z - 141200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF NY AND PA...
...SYNOPSIS...
PROGRESSIVE SHORTWAVE TROUGH CURRENTLY MOVING INTO WRN ONTARIO WILL
ADVANCE THROUGH THE LONGWAVE TROUGH PATTERN AND EJECT NEWD INTO SRN
QUEBEC EARLY TUESDAY. ASSOCIATED SURFACE LOW WILL DEEPEN IN QUEBEC
WHILE TRAILING FRONT ADVANCES THROUGH THE GREAT LAKES AND INTO THE
NERN STATES AND OH VALLEY.
...NY THROUGH THE OH VALLEY...
MODIFIED CP AIR WITH UPPER 50S TO LOW 60S DEWPOINTS WILL PERSIST IN
PRE-FRONTAL WARM SECTOR FROM THE OH VALLEY INTO THE NERN STATES. THE
BOUNDARY LAYER WILL DESTABILIZE AS DIABATIC WARMING COMMENCES...BUT
MODEST LOW LEVEL MOISTURE AND WEAK MID LEVEL LAPSE RATES SHOULD
LIMIT MLCAPE TO AOB 1200 J/KG. STRONGER FLOW ALOFT AND VERTICAL
SHEAR WILL REMAIN IN SERN CANADA IN ASSOCIATION WITH THE PROGRESSIVE
IMPULSE. HOWEVER...WINDS ARE FORECAST TO INCREASE TO BETWEEN 30 AND
40 KT IN THE 850-500 MB LAYER...BUT WITH WEAK EFFECTIVE SHEAR. THIS
ENVIRONMENT WILL SUPPORT MULTICELL CONVECTION AS STORMS DEVELOP
ALONG SEWD ADVANCING FRONT WITH A THREAT FOR MAINLY ISOLATED
DAMAGING WIND AND SMALL HAIL INTO AFTERNOON. SOME SEVERE THREAT MAY
EXTEND SWWD INTO THE OH VALLEY AREA...BUT FLOW ALOFT WILL BE WEAKER
AND STORM COVERAGE COULD BE MORE LIMITED DURING THE DAY.
...AZ...
UPPER LOW CENTERED OVER CA SHOULD BECOME A BIT MORE EASTWARD-
PROGRESSIVE BY TUESDAY...WITH ISOLATED TO SCATTERED TSTMS REMAINING
COMMON FROM THE LOWER CO RIVER VALLEY IN VICINITY TO FOUR CORNERS
AREA. AHEAD OF THE UPPER LOW...A MOIST MID LEVEL ENVIRONMENT IN
CONJUNCTION WITH STEEP LAPSE RATES AND INVERTED-V BOUNDARY LAYERS
MAY YIELD A FEW TSTMS CAPABLE OF ISOLATED DOWNBURSTS ACROSS PORTIONS
OF AZ.
..DIAL.. 09/12/2011
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