SWODY2
SPC AC 251722
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1222 PM CDT SUN SEP 25 2011
VALID 261200Z - 271200Z
...NO SVR TSTM AREAS FORECAST...
...GREAT LAKES/UPPER OH VALLEY...
A WELL-DEVELOPED UPPER-LEVEL LOW OVER THE MID TO UPPER MS VALLEY
WILL MOVE VERY SLOWLY EWD ON MONDAY. AT THE SFC...A LOW PRESSURE
AREA IS FORECAST TO MOVE IN A CIRCULAR PATTERN AROUND THE
UPPER-LEVEL LOW CENTER ACROSS THE LOWER OH VALLEY AS A COLD FRONT
ADVANCES EWD ACROSS THE UPPER OH VALLEY AND TN VALLEY. THUNDERSTORMS
SHOULD BE ONGOING ALONG THE BOUNDARY MONDAY MORNING WITH THE
CONVECTION MOVING EWD AND INCREASING IN COVERAGE DURING THE DAY.
FORECAST SOUNDINGS ALONG THE BOUNDARY AT MIDDAY DEVELOP SOME
INSTABILITY IN A MODERATELY SHEARED ENVIRONMENT WITH 0-6 KM SHEAR IN
THE 45 TO 55 KT RANGE. THE WIND PROFILE SHOULD BE MOSTLY
UNIDIRECTIONAL BUT STILL COULD SUPPORT ROTATING STORMS IF SOME OF
THE STORMS REMAIN DISCRETE DUE TO THE STRONG MID-LEVEL FLOW. THIS
COULD RESULT IN A HAIL THREAT IN THE MID-AFTERNOON WHEN INSTABILITY
BECOMES MAXIMIZED. IN ADDITION...LOW-LEVEL FLOW OF 30 KT COMBINED
WITH THE UNIDIRECTIONAL WIND PROFILES MAY ALSO SUPPORT A MARGINAL
WIND DAMAGE THREAT ESPECIALLY IF THE STORMS TEND TO LINE OUT ALONG
THE BOUNDARY. THE MAIN CONCERN IS DESTABILIZATION WITH THE MODELS
KEEPING INSTABILITY WEAK. FOR THIS REASON...A SLIGHT RISK DOES NOT
APPEAR JUSTIFIED FOR THIS OUTLOOK.
...ARKLATEX...
AN UPPER-LEVEL LOW OVER THE MID TO UPPER MS VALLEY WILL MOVE SLOWLY
EWD AS A COLD FRONT ADVANCES SWD ACROSS THE TN VALLEY AND ARKLATEX.
A NARROW CORRIDOR OF ENHANCED LOW-LEVEL FLOW IS FORECAST ALONG AND
JUST TO THE NORTH OF THE FRONT WHERE ELEVATED THUNDERSTORMS SHOULD
DEVELOP LATER MONDAY NIGHT. THE GREATEST CONVECTIVE COVERAGE IS
FORECAST ACROSS THE ARKLATEX ON THE NOSE OF A DEVELOPING LOW-LEVEL
JET. HAVE CONTINUED A 5 PERCENT SEVERE PROBABILITY LINE IN THE
ARKLATEX BUT MOVED THE THREAT SWD TO ACCOUNT FOR MODEL TRENDS. AN
ISOLATED HAIL THREAT COULD OCCUR WITH THE STRONGER STORMS ACROSS NE
TX...SRN AR AND NRN LA IN THE 06Z TO 12Z TIMEFRAME.
..BROYLES.. 09/25/2011
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