SWODY1
SPC AC 130554
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1254 AM CDT MON SEP 13 2010
VALID 131200Z - 141200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER FAR NRN KS...CNTRL AND ERN
NEB...FAR SERN SD AND WRN IA...
...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF CNTRL AND ERN NY
AS WELL AS SWRN NEW ENGLAND...
...SYNOPSIS...
A POTENT UPPER TROUGH WITH VERY COOL MID LEVEL TEMPERATURES WILL
OVERSPREAD THE NERN U.S. WHILE A 70+ KT MID LEVEL JET MAX NOSES INTO
PA/NJ BY 00Z. STRONG FORCING ASSOCIATED WITH THE SFC AND UPPER LEVEL
TROUGHS WILL ALLOW FOR A FEW SEVERE STORMS ACROSS PORTIONS OF NY AND
SRN NEW ENGLAND THIS AFTERNOON. TO THE W...RICH BOUNDARY LAYER
MOISTURE IS IN PLACE ACROSS THE SRN PLAINS...ON THE W SIDE OF A
SURFACE HIGH CENTERED OVER THE TN VALLEY. THIS AIR MASS WILL SPREAD
NWD BENEATH A STEEP MID LEVEL LAPSE RATE PROFILE AS WEAK LOW
PRESSURE DEVELOPS ACROSS THE CNTRL HIGH PLAINS. STRONG HEATING AND
DESTABILIZATION IS EXPECTED TO LEAD TO SCATTERED SEVERE STORMS BY
LATE AFTERNOON OVER PORTIONS OF KS AND NEB.
...KS/NEB/SD/IA...
WEAK CONVECTION MAY BE ONGOING ACROSS SRN KS AND OK EARLY MON
MORNING...BUT THIS ACTIVITY IS NOT EXPECTED TO BE SEVERE. DURING THE
DAY...MID/UPPER 60S F DEWPOINTS WILL SPREAD NWD INTO KS AND
NEB...WITH STRONG HEATING. LOW LEVEL WINDS WILL BACK WITH TIME AS
WEAK LOW PRESSURE DEVELOPS ACROSS THE HIGH PLAINS. ALTHOUGH
CONVERGENCE WILL LIKELY BE WEAK...VERY STEEP LOW TO MID LEVEL LAPSE
RATES WILL EXIST...AS WILL STRONG INSTABILITY WITH NO CIN BY LATE
AFTERNOON. AS A RESULT...SEVERE STORMS MAY ERUPT ANYWHERE FROM
CNTRL/NWRN KS INTO SWRN AND CNTRL NEB ONCE CIN IS ERODED. LONG
HODOGRAPHS AND STEEP LAPSE RATES WILL LIKELY RESULT IN SUPERCELLS
WITH HAIL...SOME POSSIBLY VERY LARGE...AS WELL AS DAMAGING WIND
GUSTS. AFTER 00Z...THE LOW LEVEL JET WILL INCREASE OUT OF THE S TO
25-35 KT...AND WILL SUPPORT ONGOING ACTIVITY AS WELL AS NEW ACTIVITY
FARTHER N WHERE ISENTROPIC LIFT WILL BE ON THE INCREASE. THE SRN
ACTIVITY MAY MERGE INTO A SEVERE MCS WITH ENHANCED WIND
THREAT...WITH MAINLY A HAIL THREAT WITH THE NRN ACTIVITY.
...NY INTO SWRN NEW ENGLAND...
CONVECTION IS LIKELY TO BE ONGOING ACROSS FAR WRN NY/NEAR LAKE
ONTARIO AT 12Z IN ASSOCIATION WITH A DEVELOPING LOW PRESSURE TROUGH
AND UPPER VORT. THIS ACTIVITY MAY STRENGTHEN AS IT DEVELOPS EWD AND
AS THE ATMOSPHERE DESTABILIZES FURTHER. VERY COOL MID LEVEL
TEMPERATURES WILL COMBINE WITH AREAS OF HEATING TO PRODUCE A STEEP
LOW TO MID LEVEL LAPSE RATE ENVIRONMENT BY MID AFTERNOON. THIS WILL
HELP MAXIMIZE CONVECTIVE INSTABILITY DESPITE RELATIVELY LOW BOUNDARY
LAYER DEWPOINTS IN THE LOWER 50S F. LONG HODOGRAPHS AND COOL
TEMPERATURES ALOFT WILL FAVOR HAIL PRODUCTION...WHILE FAST STORM
MOTIONS AND A RELATIVELY DRY BOUNDARY LAYER STRUCTURE FAVORS STRONG
TO SEVERE WIND GUSTS.
..JEWELL/SMITH.. 09/13/2010
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