SWODY1
SPC AC 310557
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT SAT MAY 31 2008
VALID 311200Z - 011200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF SERN NY...WRN
MA...NWRN CT...WRN NJ...ERN PA...DE...CNTRL/ERN MD...NRN VA...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PART OF THE
CNTRL/SRN PLAINS EWD ACROSS THE MID-SOUTH AND ALONG THE ERN
SEABOARD...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A SMALL PART OF THE UPR MS
VLY...
...SYNOPSIS...
COMPLEX UPR TROUGH OVER THE UPR GRTLKS/MIDWEST EARLY SATURDAY WILL
MOVE TO NEW ENGLAND AND MID-ATLANTIC REGIONS BY SATURDAY NIGHT.
UPSTREAM...UPR LOW OFF THE WA CST WILL EDGE CLOSER TO SHORE WHILE A
WEAKER DISTURBANCE GLANCES OFF THE SUBTROPICAL RIDGE OVER THE SRN
U.S. AND EJECTS NEWD ACROSS THE NRN INTERMOUNTAIN WEST.
IN THE LWR LVLS...PRIMARY SFC LOW ASSOCD WITH THE GRTLKS UPR SYSTEM
WILL MOVE INTO WRN QUEBEC WITH THE COLD FRONT ADVANCING SEWD THROUGH
THE GRTLKS AND THE OH VLY. PARTS OF THE FRONT WILL BE AUGMENTED BY
OUTFLOW FROM NOCTURNAL MCS OVER THE OH VLY. MEANWHILE...A LEE
TROUGH WILL BECOME ESTABLISHED FROM ERN NY SWD INTO THE CAROLINAS.
TO THE WEST...TRAILING PORTION OF THE AFOREMENTIONED COLD
FRONT/PRE-FRONTAL BOUNDARY WILL EXTEND WWD ACROSS THE MID-SOUTH AND
INTO THE SRN HIGH PLAINS. THIS FEATURE WILL MOVE LITTLE AS IT
BECOMES ALIGNED WITH LARGELY ZONAL FLOW REGIME.
...NEW ENGLAND TO THE CAROLINAS...
WEAKENING MCS WILL BE LOCATED W OF THE APLCN CHAIN AT 12Z SATURDAY.
DOWNSTREAM CLOUDS SHOULD GRADUALLY THIN DURING THE MORNING AND ALLOW
FOR MODEST HEATING TO OCCUR INVOF LEE-TROUGH FROM SERN NY SWD INTO
THE CAROLINAS. THOUGH SHORT TERM MODELS ARE AGGRESSIVE IN LOW-LEVEL
MOISTURE RETURN...AT LEAST MID 60S SFC DEW POINTS SHOULD ADVECT NWD
INTO ERN PA/SERN NY WITH UPR 60S SOUTH OF THE MASON DIXON LINE.
SUFFICIENT DESTABILIZATION WILL BE FAVORABLE FOR TSTMS TO
DEVELOP...WITH THE LEE TROUGH LIKELY BEING THE PRIMARY INITIATING
ZONE...PARTICULARLY FROM ERN NY SWD INTO CNTRL VA.
A 60-65 KT WLY H5 JET ATOP WSWLY LOW-LEVEL FLOW WILL BOOST BULK
SHEAR SUFFICIENT FOR SUPERCELLS AND BOW ECHOES. PRIMARY THREATS
WILL BE DMGG WIND GUSTS AND LARGE HAIL. HOWEVER...CHANNELED SLY
FLOW ACROSS SERN NY...EXTREME WRN MA...NWRN CT MAY CONTRIBUTE TO AN
ENHANCED RISK OF A FEW TORNADOES.
TSTMS SHOULD PEAK AND MOVE OFFSHORE BY EARLY EVENING IN ALL EXCEPT
PARTS OF SRN VA/CNTRL-ERN CAROLINAS WHERE LINGERING STORMS MAY
REMAIN STG-SVR WELL INTO THE EVENING.
FARTHER N...ACROSS UPSTATE NY...TSTMS WILL PROBABLY FORM ALONG THE
PRIMARY COLD FRONT OVER SRN ONTARIO DURING THE LATE MORNING AND
ROTATE INTO UPSTATE NY. HERE...VERTICAL SHEAR WILL BE COMPARATIVELY
WEAKER...BUT COLDER TEMPERATURES ALOFT MAY FOSTER STG-SVR STORMS
WITH HAIL/GUSTY WINDS.
...SRN PLAINS...
ESE LOW-LEVEL FLOW WILL MAINTAIN RESERVOIR OF MID-UPR 60S DEW POINTS
BENEATH STEEP MID-LEVEL LAPSE RATES. STRONG HEATING WILL CONTRIBUTE
TO VERY UNSTABLE CONDITIONS WITH MLCAPES APPROACHING 3000 J/KG
ACROSS SRN KS/NRN OK BY MID-AFTN. TSTMS WILL LIKELY DEVELOP INVOF A
SFC TROUGH OVER SRN KS DURING THE MID-AFTN. REGION WILL RESIDE
ALONG SRN FRINGE OF 50-55 KTS OF WLY FLOW ALOFT AND SUPERCELLS WITH
VERY LARGE HAIL AND ISOLD TORNADOES WILL BE LIKELY. ACTIVITY IS
EXPECTED TO GROW UPSCALE INTO AN MCS WITH DMGG WIND GUSTS/HAIL
SATURDAY NIGHT ACROSS NRN/CNTRL OK INTO SWRN MO/NWRN AR.
...UPR MS VLY...
A WEAK DISTURBANCE DROPPING DOWN THE BACKSIDE OF THE DEPARTING
LARGER SCALE TROUGH WILL CONTRIBUTE TO DIURNALLY ENHANCED TSTMS OVER
PARTS OF MN SEWD INTO NWRN IL/ERN IA SATURDAY AFTN/EARLY EVE. COLD
MID-LEVEL TEMPERATURES COMBINED WITH ROUGHLY 35-40 KTS OF NWLY
MID-LEVEL FLOW WILL BE SUFFICIENT FOR A FEW SVR STORMS WITH LARGE
HAIL AND DMGG WINDS GUSTS.
..RACY/HURLBUT.. 05/31/2008
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