SWODY1
SPC AC 101238
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0738 AM CDT WED SEP 10 2008
VALID 101300Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE
CENTRAL/NORTHERN PLAINS...
...NEB/SD...
A WEAK POSITIVELY TILTED UPPER TROUGH WILL BE PRESENT TODAY OVER THE
MOUNTAINOUS WEST...WHILE WEAK LEAD SHORTWAVE TROUGH NOW OVER WY
TRACKS EASTWARD INTO THE PLAINS. MORNING SATELLITE LOOPS SUGGEST
THAT RELATIVELY CLEAR SKIES WILL OCCUR OVER PARTS OF
SD/NEB...ALLOWING AIRMASS TO HEAT/DESTABILIZE. SOUTHERLY LOW LEVEL
WINDS AHEAD OF APPROACHING UPPER TROUGH WILL ALSO HELP TO TRANSPORT
MOIST AIR INTO REGION WITH 60S DEWPOINTS EXPECTED BY LATE AFTERNOON.
STEEP MID LEVEL LAPSE RATES SHOWN ON 12Z LBF SOUNDING SUGGEST THAT
MODERATE INSTABILITY WILL DEVELOP THIS AFTERNOON ALONG AN AXIS FROM
SOUTHWEST NEB INTO SOUTH CENTRAL SD.
FORECAST SOUNDINGS SUGGEST THAT A STRONG CAPPING INVERSION WILL BE
MAINTAINED THROUGH MUCH OF THE DAY...UNTIL STRONGER FORCING EMERGES
FROM CENTRAL ROCKIES LATE IN THE DAY. SCATTERED HIGH-BASED
THUNDERSTORMS ARE THEN LIKELY TO DEVELOP ALONG WEST EDGE OF
INSTABILITY AXIS AND SPREAD EAST-NORTHEASTWARD DURING THE EVENING.
EFFECTIVE SHEAR VALUES OF 25-30 KNOTS SUGGEST THAT ORGANIZED
MULTICELL STORMS WILL OCCUR...CAPABLE OF LARGE HAIL AND DAMAGING
WINDS. SEVERE THREAT MAY PERSIST THROUGH THE EVENING AND DEVELOP
INTO PARTS OF EASTERN SD.
...FL...
HURRICANE IKE CONTINUES TO MOVE SLOWLY WESTWARD AND AWAY FROM FL. A
FEW ISOLATED SUPERCELLS AFFECTED EXTREME SOUTHWEST FL EARLY THIS
MORNING...BUT THIS OUTER BAND HAS WEAKENED AND MOVED OFFSHORE.
UPSTREAM TRENDS AND MOVEMENT OF IKE SUGGEST THAT TORNADO THREAT IS
DIMINISHING OVER SOUTH FL AND THE KEYS.
...AZ...
A RATHER COLD UPPER TROUGH WILL TRACK SOUTHWARD ACROSS
CENTRAL/SOUTHERN CA TODAY...WITH HEIGHT FALLS AND INCREASING
SOUTHWEST FLOW ALOFT OVER MUCH OF AZ. MUCH OF THIS REGION WILL SEE
STRONG HEATING AND THE DEVELOPMENT OF AT LEAST MODERATE INSTABILITY.
A FEW INTENSE STORMS MAY DEVELOP DURING THE AFTERNOON AND EVENING
CAPABLE OF HAIL AND GUSTY WINDS. ORGANIZED SEVERE STORMS ARE NOT
CURRENTLY ANTICIPATED.
..HART.. 09/10/2008
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