SPC AC 031716
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1216 PM CDT TUE OCT 03 2006
VALID 041200Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS WED AFTN/EVE ACROSS THE OHIO
VALLEY AND LOWER GREAT LAKES INTO PARTS OF THE NORTHEAST....
MODELS INDICATE THAT BROAD TROUGHING WILL GRADUALLY EVOLVE IN THE
NORTHERN BRANCH OF THE POLAR WESTERLIES...ACROSS THE EASTERN
CANADIAN PROVINCES DURING THIS FORECAST PERIOD. THIS IS FORECAST TO
OCCUR GENERALLY IN PHASE WITH THE SOUTHERN BRANCH...WITH A
SIGNIFICANT EMBEDDED SHORT WAVE TROUGH PROGRESSING EAST OF THE UPPER
GREAT LAKES/MISSISSIPPI VALLEY REGION...INTO/THROUGH THE LOWER GREAT
LAKES AND NORTHEAST BY 12Z THURSDAY.
UPSTREAM...SUBTROPICAL RIDGING IS PROGGED TO PERSIST ACROSS THE
SOUTH CENTRAL STATES AND GULF COAST. SOME AMPLIFICATION OF RIDGE
NORTHWARD THROUGH THE NORTHERN HIGH PLAINS WILL PROBABLY OCCUR...
AHEAD OF A CLOSED LOW DEVELOPING IN THE SOUTHERN STREAM...ALONG
PACIFIC COASTAL AREAS.
...EAST OF ROCKIES...
MODELS INDICATE THAT THE FAIRLY VIGOROUS MID-LEVEL IMPULSE
PROGRESSING EAST OF THE GREAT LAKES REGION WILL BE ACCOMPANIED BY A
DEEPENING SURFACE LOW ACROSS UPSTATE NEW YORK INTO NORTHERN NEW
ENGLAND MIDDAY THROUGH EARLY EVENING WEDNESDAY. THIS FEATURE... AND
TRAILING SURFACE FRONT ADVANCING SOUTH OF THE GREAT LAKES INTO THE
OHIO VALLEY...ARE EXPECTED TO PROVIDE FORCING/FOCUS FOR DEEP
CONVECTIVE DEVELOPMENT AS AIR MASS DESTABILIZES WITH DAYTIME
HEATING.
DESTABILIZATION IS EXPECTED TO BE STRONGEST WHERE BETTER LOW-LEVEL
MOISTURE RETURN OCCURS...THROUGH THE LOWER OHIO VALLEY...AROUND
RETREATING SOUTHEASTERN U.S./WESTERN ATLANTIC SURFACE RIDGE.
HOWEVER...STRONGER MID/UPPER FORCING FOR UPWARD VERTICAL MOTION IS
EXPECTED TO SHIFT WITH STRONGER WIND FIELDS ALONG THE CANADIAN/U.S.
BORDER...EAST OF THE LOWER GREAT LAKES INTO THE NORTHEAST BY
WEDNESDAY AFTERNOON.
THOUGH WEAK...INSTABILITY WILL PROBABLY BECOME SUFFICIENT TO SUPPORT
BROKEN CONVECTIVE LINE IN WARM SECTOR OF SURFACE LOW...WEST
SOUTHWESTWARD ALONG FRONTAL ZONE ADVANCING EAST/SOUTHEAST OF THE
LOWER GREAT LAKES REGION. EMBEDDED WITHIN A FAVORABLY SHEARED 30 TO
50 KT MEAN FLOW FIELD...POTENTIAL WILL EXIST FOR DAMAGING
WINDS...PERHAPS SOME MARGINALLY SEVERE HAIL AND AN ISOLATED TORNADO
OR TWO...ACROSS PENNSYLVANIA AND NEW YORK STATE INTO PARTS OF
NORTHERN NEW ENGLAND. THREAT MAY PERSIST INTO EARLY WEDNESDAY
EVENING BEFORE DIMINISHING.
BROKEN CONVECTIVE LINE MAY DEVELOP FARTHER UPSTREAM...THROUGH MUCH
OF THE REMAINDER OF THE NORTHERN HALF OF THE OHIO VALLEY...BY LATE
WEDNESDAY AFTERNOON. THOUGH SHEAR/FLOW FIELDS WILL BE SUBSTANTIALLY
WEAKER...MORE FAVORABLE THERMODYNAMIC ENVIRONMENT ...WITH STEEPER
LOW-LEVEL LAPSE RATES AND CAPE OF 1000 TO 2000 J/KG...MAY
COMPENSATE....PROVIDING A RISK FOR DAMAGING WINDS/HAIL IN STRONGER
CELLS.
...PACIFIC COAST INTO ROCKIES...
FAVORABLE LARGE-SCALE FORCING NORTHEAST OF DEVELOPING CLOSED LOW IS
EXPECTED TO FOCUS THE PRIMARY CONVECTIVE DEVELOPMENT IN A BROAD
ARC...ACROSS THE NORTHERN INTERMOUNTAIN REGION INTO THE FOUR CORNERS
REGION...WEDNESDAY. DUE TO LIMITED MOISTURE...CAPE WILL PROBABLY BE
RATHER WEAK. BUT...SIZABLE LOW-LEVEL TEMPERATURE/DEW POINT SPREADS
AND DOWNWARD TRANSFER OF MOMENTUM ASSOCIATED WITH A SEASONABLY
STRONG SOUTHWESTERLY MID/HIGH LEVEL JET COULD SUPPORT LOCALIZED
DOWNBURSTS.
..KERR.. 10/03/2006
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
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