SWODY2
SPC AC 071728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT SUN SEP 07 2008
VALID 081200Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL
PLAINS AND MID TO UPPER MS VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN AND CNTRL
FL...
...CNTRL PLAINS/MID TO UPPER MS VALLEY...
ZONAL FLOW FROM THE UPPER MS VALLEY EWD INTO THE GREAT LAKES TONIGHT
WILL BECOME WSWLY MONDAY AHEAD OF AN APPROACHING UPPER-LEVEL TROUGH
IN THE PLAINS STATES. THIS FEATURE WILL GRADUALLY AMPLIFY AS A
LOW-LEVEL JET MOVES QUICKLY NEWD FROM THE CNTRL PLAINS INTO THE
LOWER OH VALLEY. MODEL FORECASTS ARE IN AGREEMENT WITH AN ELEVATED
STORM CLUSTER ON THE NORTH SIDE OF THE LOW-LEVEL JET MOVING EWD
ACROSS THE CNTRL PLAINS INTO THE MID MO VALLEY MONDAY MORNING.
STRONG VERTICAL SHEAR AND RELATIVELY STEEP MID-LEVEL LAPSE RATES
EVIDENT ON FORECAST SOUNDINGS SHOULD SUPPORT A MARGINAL HAIL THREAT
WITH THIS THUNDERSTORM CLUSTER.
THE ELEVATED STORM CLUSTER OVER THE CNTRL PLAINS MAY CONTINUE EWD
ACROSS NRN MO AND SRN IA MONDAY AFTERNOON WITH SFC-BASED
THUNDERSTORMS INITIATING AS SFC TEMPS HEAT UP ON THE NRN EDGE OF AN
AXIS OF MODERATE INSTABILITY FROM ERN KS INTO NCNTRL MO. A
WELL-DEFINED 60 TO 75 KT MID-LEVEL JET OVER THE UPPER MIDWEST SHOULD
CREATE A STRONG GRADIENT IN VERTICAL SHEAR SWD ACROSS IA AND MO WITH
FORECAST SOUNDINGS SHOWING ABOUT 50 KT OF 0-6 KM SHEAR OVER SRN IA
DROPPING TO ABOUT 30 KT OVER CNTRL MO. THIS AMOUNT OF VERTICAL SHEAR
SHOULD BE SUPPORTIVE OF SUPERCELLS AND BOWING LINE SEGMENTS LATE
MONDAY AFTERNOON INTO THE EARLY EVENING.
MODEL FORECASTS SUGGEST THE UPPER-LEVEL TROUGH WILL BE QUITE FOCUSED
AND THE POTENTIAL FOR A SEVERE MCS APPEARS FAIRLY CERTAIN. LOW-LEVEL
SHEAR EVIDENT ON FORECAST SOUNDINGS SHOULD BE ADEQUATE FOR A FEW
TORNADOES WITH SUPERCELLS AND THE MORE ORGANIZED BOW ECHOS. THE
MODELS ALSO SHOW A WARM FRONT FROM NRN MO EXTENDING EWD INTO WRN MO
WHERE STRONG LOW-LEVEL SHEAR...LOW LCL-HEIGHTS AND ABUNDANT MOISTURE
IS FORECAST. THIS SHOULD BE SUFFICIENT FOR AN ISOLATED TORNADO
THREAT ESPECIALLY WITH SUPERCELLS THAT TRACK EWD ALONG OR NEAR THE
BOUNDARY. THE SHEAR AND INSTABILITY ALSO SHOULD SUPPORT LARGE HAIL
WITH THE MORE DOMINANT SUPERCELLS. WIND DAMAGE APPEARS MOST LIKELY
WITH LINE SEGMENTS THAT DEVELOP IN THE MODERATELY UNSTABLE AIR SOUTH
OF THE FRONT WHERE LOW-LEVEL LAPSE RATES SHOULD BE QUITE STEEP IN
THE LATE AFTERNOON AND EARLY EVENING. MODEL FORECASTS MOVE AN MCS
INTO THE NRN OH VALLEY DURING THE LATE EVENING AND OVERNIGHT PERIOD.
INSTABILITY AND VERTICAL SHEAR ON FORECAST SOUNDINGS MAY SUPPORT A
MARGINAL SEVERE THREAT WITH THIS CONVECTIVE CLUSTER.
...SRN AND CNTRL FLORIDA...
HURRICANE IKE IS FORECAST BY THE NATIONAL HURRICANE CENTER TO MOVE
WWD ACROSS THE ISLAND OF CUBA MONDAY AND MONDAY NIGHT WITH THE NRN
RAINBANDS SPREADING ACROSS SRN AND CNTRL FLORIDA. LOW-LEVEL SHEAR
PROFILES ARE FORECAST TO GRADUALLY INCREASE ACROSS SRN FL DURING THE
AFTERNOON AND EVENING AS THE STRONGER WINDS APPROACH AND THE CENTER
OF IKE PASSES BY TO THE SOUTH. INITIALLY...A MARGINAL TORNADO THREAT
SHOULD EXIST WITH THE FIRST RAINBANDS THAT MOVE INLAND ACROSS FL
MONDAY MORNING. HOWEVER...THE TORNADO THREAT MAY BECOME GREATER
DURING THE AFTERNOON AS INSTABILITY STRENGTHENS...LCL HEIGHTS DROP
AND LOW-LEVEL SHEAR INCREASES. THE TORNADO THREAT MONDAY AFTERNOON
AND EVENING SHOULD PERSIST INTO THE OVERNIGHT PERIOD.
..BROYLES.. 09/07/2008
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