SWODY2
SPC AC 051730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT SUN SEP 05 2010
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE UPPER MS
VALLEY...
...SYNOPSIS...
A VIGOROUS UPPER TROUGH WILL CONTINUE EWD ACROSS THE NRN
PLAINS...TAKING ON A NEGATIVE TILT AS IT APPROACHES THE UPPER MS
VALLEY BY EVENING. AT THE SURFACE...A LOW WILL MOVE FROM NEBRASKA
INTO MN...BECOMING OCCLUDED OVER CNTRL/SRN MN BY LATE IN THE DAY.
STRONG FORCING NEAR THE LOW...AND ALONG A TRAILING COLD FRONT WILL
BE THE PRIMARY FOCUS FOR SEVERE STORMS LATE MONDAY. OTHER ISOLATED
ACTIVITY WILL ALSO BE POSSIBLE FARTHER S ALONG THE FRONT FROM MO
INTO SRN KS/NRN OK. ELSEWHERE...WIND PROFILES MAY BECOME FAVORABLE
FOR ISOLATED TORNADOES ACROSS THE LOWER/MIDDLE TX COAST CONTINGENT
ON AT LEAST WEAK TROPICAL CYCLONE FORMATION.
...IA...SRN MN...WRN WI...
MAINLY ELEVATED CONVECTION WILL BE ONGOING ACROSS SD NEAR A
DEEPENING COLD FRONT...ALTHOUGH THIS ACTIVITY SHOULD REMAIN
SUB-SEVERE WITH ONLY SMALL HAIL POSSIBLE. ANOTHER AREA OF ONGOING
ACTIVITY IS LIKELY TO BE OVER SRN WI/NRN IL ALONG A WARM FRONT AND
NEAR THE MOST OF A SWLY LOW LEVEL JET. HERE...FORECAST SOUNDINGS
INDICATE STEEP MID TO UPPER LEVEL LAPSE RATES WILL BE IN PLACE WITH
ELEVATED PARCELS LIFTED NEAR 700 MB YIELDING AROUND 1000 J/KG
MUCAPE. THUS...SOME OF THIS ACTIVITY MAY CONTAIN HAIL EARLY.
BY LATE AFTERNOON...ATTENTION WILL SHIFT WWD TO THE COLD FRONT. THE
MAIN UNCERTAINTY IS IN REGARD TO THE QUALITY OF THE WARM SECTOR
INSTABILITY AND CAPPING. A STOUT EML WILL BE IN PLACE FOR MOST OF
THE DAY...WITH CIN DECREASING ONLY ONCE THE STRONG FORCING ARRIVES.
THUS...MOST OF THE SLIGHT RISK AREA WILL REMAIN STORM-FREE UNTIL
LATE AFTERNOON/EARLY EVENING...WHEN STRONG FORCING ERODES THE CAP.
THE MOST LIKELY AREA FOR SEVERE WILL BE NEAR THE SURFACE
LOW/OCCLUDED FRONTAL ZONE OVER CNTRL/SRN MN AND WRN WI. SRN PORTIONS
OF THE SLIGHT RISK AREA INCLUDING MUCH OF CNTRL IA IS MORE
CONDITIONAL AS STORM COVERAGE WILL BE IN QUESTION DUE TO CAPPING
CONCERNS. WIND PROFILES WILL BE QUITE STRONG ACROSS THE ENTIRE
REGION...AND SUPERCELLS...EITHER SINGLE CELL OR EMBEDDED WITHIN A
LINE...WILL BE POSSIBLE WITH LARGE HAIL...DAMAGING WINDS...AND
ISOLATED TORNADOES POSSIBLE. GIVEN THE STRENGTH OF THE SHEAR
PROFILES...A STRONG TORNADO CANNOT BE RULED OUT...BUT CONCERNS ABOUT
STORM COVERAGE AND QUALITY OF THE BOUNDARY LAYER MOISTURE WILL
PRECLUDE INTRODUCTION OF HIGHER PROBS AT THIS TIME.
...S TX...
WHILE SIGNIFICANT DIFFERENCES EXIST BETWEEN VARIOUS FORECAST
MODELS...THERE APPEARS TO BE A HIGH LIKELIHOOD OF TROPICAL CYCLONE
DEVELOPMENT OVER THE WRN GULF OF MEXICO OVER THE NEXT 48 HOURS /SEE
OFFICIAL NATIONAL HURRICANE CENTER FORECAST FOR MORE INFORMATION/.
ASSUMING THIS IS WHAT OCCURS...AND USING THE NAM SOLUTION AS AN
ENVIRONMENTAL PROXY...THERE WOULD BE A THREAT OF ISOLATED TORNADOES
ACROSS S TX AS FORECAST SOUNDINGS SHOW SIGNIFICANT LOW LEVEL VEERING
AND HODOGRAPHS FAVORABLE FOR SUPERCELLS. IN ADDITION...DEWPOINTS IN
THE UPPER 70S WOULD MAXIMIZE INSTABILITY IN OTHERWISE WARM PROFILES.
..JEWELL.. 09/05/2010
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