DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 111247
SWODY1
SPC AC 111245

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0745 AM CDT TUE SEP 11 2007

VALID 111300Z - 121200Z

..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF UPSTATE NY AND
VT...

..SYNOPSIS...
AN ACTIVE...CHANGEABLE PATTERN WILL PREVAIL FROM THE GRT LKS TO NEW
ENGLAND THIS PERIOD...WHILE LOW AMPLITUDE RIDGING PERSISTS ACROSS
MUCH OF THE WEST. POTENT SHORTWAVE TROUGH NOW AMPLIFYING SE ACROSS
THE UPR GRT LKS WILL PHASE WITH MORE SLOWLY-MOVING IMPULSE NOW OVER
THE OH VLY...RESULTING IN A DEEP BUT PROGRESSIVE CLOSED LOW OVER
CNTRL QUEBEC WEDNESDAY MORNING.

AT LWR LVLS...SFC WAVE LOW NOW OVER LK ONTARIO SHOULD SLOWLY DEEPEN
AS IT MOVES NE INTO QUEBEC LATER TODAY. MORE SUBSTANTIAL DEEPENING
SHOULD OCCUR TONIGHT AS UPR LVL CIRCULATION AMPLIFIES OVER REGION.
WEAK COLD FRONT TRAILING SW FROM THE WAVE EXPECTED TO MOVE ONLY
SLOWLY E ACROSS UPSTATE NY AND PA TODAY...BEFORE ACCELERATING ESE
INTO NEW ENGLAND AND THE MID ATLANTIC STATES TONIGHT.

..UPSTATE NY/VT...
APPROACH OF AMPLIFYING UPR TROUGH WILL SUBSTANTIALLY ENHANCE LARGE
SCALE ASCENT/DEEP WIND FIELD ACROSS UPSTATE NY LATER TODAY/ TONIGHT.
CLOUDS/PRECIP ASSOCIATED WITH LEAD UPR IMPULSE WILL STRONGLY LIMIT
LOW LVL DESTABILIZATION. BUT FOCUSED LOW LVL ASCENT ALONG
STRENGTHENING COLD FRONT AND MID LVL COOL ADVECTION SHOULD BE
SUFFICIENT FOR DEVELOPMENT OF A LINE OF LOW-TOPPED STORMS FROM LK
ONTARIO S INTO THE FINGER LKS REGION AND PERHAPS NRN PA AS SBCAPE
INCREASES TO NEAR 500 J/KG. 50 KT UNIDIRECTIONAL SWLY MID LVL FLOW
ROUGHLY PARALLEL TO BOUNDARY AND FAIRLY MOIST PROFILES /PW AOA 1.25
INCHES/ MAY YIELD SMALL SCALE BOWING SEGMENTS WITH HIGH WIND AND
POSSIBLY A BRIEF TORNADO. ACTIVITY SHOULD WEAKEN AS IT OUT-RUNS
LOW-LVL INSTABILITY AXIS FARTHER E INTO WRN NEW ENGLAND.

..MID ATLANTIC CST...
A FEW STRONG TO LOCALLY SVR STORMS MAY FORM THIS AFTERNOON THROUGH
EARLY THIS EVENING OVER THE CHESAPEAKE BAY/ DELMARVA PENINSULA AS
REGION IS GLANCED BY TAIL END OF LEAD UPR IMPULSE NOW IN THE OH VLY.
STRENGTHENING UNIDIRECTIONAL WSW FLOW AND RESIDUAL AXIS OF RICH LOW
LVL MOISTURE INVOF OLD FRONT MAY SUPPORT DEVELOPMENT OF A FEW BOWING
SEGMENTS WITH HIGH WIND.

..NRN MI...
AMPLIFYING UPR TROUGH WILL YIELD STRENGTHENING DEEP CYCLONIC FLOW
ACROSS THE UPR GRT LKS TODAY. ASSOCIATED ONSET OF MID LVL COLD
ADVECTION WILL BE FAVORABLY-TIMED WITH LOW LVL DIURNAL
DESTABILIZATION AND POSSIBLE LAKE-ENHANCED FLUXES TO FOSTER
LOW-TOPPED STORM DEVELOPMENT OVER NRN MI. THE STRONGEST ACTIVITY
SHOULD FOCUS ALONG SHALLOW COLD FRONT ON LEADING EDGE OF UPR SYSTEM
THIS AFTERNOON...AND COULD YIELD MARGINALLY SVR HAIL AND/OR STRONG
WIND GUSTS.

..AZ/NM...
SCTD AFTERNOON TSTMS ARE EXPECTED OVER THE HIGHER TERRAIN OF
CNTRL/NRN AZ INTO PARTS OF NM AND SRN UT...ON SRN FRINGE OF
ELONGATING UPR DISTURBANCE. WHILE VERTICAL SHEAR WILL BE WEAK...
STEEP LAPSE RATES WITH SBCAPE TO AROUND 800 J/KG MAY SUPPORT A FEW
STRONG UPDRAFTS CAPABLE OF HAIL AND/OR LOCALLY WIND THROUGH THIS
EVENING.

.CORFIDI/JEWELL.. 09/11/2007

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