SWODY1
SPC AC 060600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT TUE OCT 06 2009
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM SOUTH CENTRAL TX TO THE
MID-SOUTH/LOWER MS RIVER VALLEY...
...SYNOPSIS...
SPLIT LONGWAVE FLOW WILL CONTINUE TO PREVAIL OVER THE WESTERN
CONUS...AS AN UPPER TROUGH/ATTENDANT STRONG JET TRANSITIONS EASTWARD
OVER THE MIDWEST/WESTERN GREAT LAKES...WHILE AN INCREASINGLY CUT-OFF
UPPER LOW SHIFTS SOUTHWARD OVER CA. IN ASSOCIATION WITH THE CENTRAL
STATES UPPER TROUGH...A SURFACE LOW WILL CONTINUE TO STEADILY
DEEPEN/TRANSITION NORTHEASTWARD OVER THE UPPER MIDWEST/WESTERN GREAT
LAKES AS AN EASTWARD ACCELERATING COLD FRONT SPREADS EASTWARD ACROSS
THE MIDDLE MS VALLEY/OZARKS/OH VALLEY/MID-SOUTH. THE WEST-SOUTHWEST
PORTION OF THE COLD FRONT WILL SETTLE SOUTH-SOUTHEASTWARD ACROSS THE
ARKLATEX/TX/LOWER MS RIVER VALLEY THROUGH THE PERIOD.
...TX/ARKLATEX TO LOWER/MIDDLE MS RIVER VALLEY...
A BROAD CYCLONIC BELT OF INTENSIFYING DEEP LAYER TROPOSPHERIC
FLOW...WITH 130-150 KT AND 60-100 KT AT 250 MB/500 MB
RESPECTIVELY...IS EXPECTED OVER THE MIDWEST AND ADJACENT PORTIONS OF
THE MID-SOUTH ATTENDANT TO THE ADVANCING UPPER TROUGH OVER THE UPPER
MIDWEST. OWING TO A STRONG LOW LEVEL JET/ELEVATED MOISTURE TRANSPORT
REGIME...SHOWERS/TSTMS WILL LIKELY BE COMMON AT THE BEGINNING OF THE
PERIOD FROM PORTIONS OF THE SOUTH CENTRAL PLAINS/ARKLATEX TO THE
OZARKS/MIDDLE MS VALLEY. A FEW OF THESE STORMS COULD PRODUCE HAIL TO
SEVERE LEVELS EARLY IN THE DAY...BUT A POTENTIALLY MORE ORGANIZED
SEVERE RISK SHOULD EVOLVE LATER IN THE AFTERNOON/EARLY EVENING
ACROSS THE MID-SOUTH/TN VALLEY AND ARKLATEX/CENTRAL TX.
WITH A MOISTURE-RICH AIRMASS ESTABLISHED ACROSS THE SOUTHERN
PLAINS...ESPECIALLY GIVEN EARLY DAY PRECIPITATION/CLOUD COVER...THE
DETAILS OF THE EVENTUAL NORTHEASTWARD EXTENT OF THE TRUE WARM/MOIST
SECTOR AHEAD OF THE ACCELERATING COLD FRONT IS A BIT UNCERTAIN
ACROSS THE MID-SOUTH/TN VALLEY THIS AFTERNOON/EARLY EVENING.
NONETHELESS...STRENGTHENING WIND FIELDS ALOFT/MODEST HEIGHT FALLS
AND AN INCREASINGLY MOIST /PERHAPS NEARING 70F SURFACE DEWPOINTS/
AND DIURNALLY UNSTABLE AIRMASS IS SUGGESTIVE OF AN INCREASING SEVERE
RISK DURING THE AFTERNOON ACROSS THE ARKLATEX VICINITY INTO PORTIONS
OF MS/WESTERN TN ALONG/AHEAD OF THE COLD FRONT. MODERATE INSTABILITY
AND STRONG DEEP LAYER SHEAR WILL SUPPORT FAST MOVING STORMS/POSSIBLE
SMALL BOWS WITH DAMAGING WINDS AS THE PRIMARY HAZARD. RELATIVELY
STRONG 1-2 KM FLOW AND AMPLE LOW LEVEL SRH /150-300 M2 PER S2/ WILL
SUPPORT THE POSSIBILITY OF A FEW TORNADOES WITH ANY QUASI-DISCRETE
SUPERCELLS AND/OR LINE EMBEDDED CIRCULATIONS.
FARTHER SOUTHWEST...ADDITIONAL DEVELOPMENT WILL LIKELY OCCUR FROM
THE ARKLATEX INTO PORTIONS OF CENTRAL TX/HILL COUNTRY IN THE
IMMEDIATE VICINITY OF THE SOUTH-SOUTHEASTWARD ADVANCING COLD FRONT.
LIMITED FORCING ON THE LARGE SCALE...GRADUALLY RISING HEIGHT
FALLS/WEAK MID LEVEL LAPSE RATES...AND THE UNDERCUTTING NATURE OF
THE FRONT SUGGEST THE SEVERE RISK MAY NOT BE PARTICULARLY
LONG-LIVED/WELL-ORGANIZED THIS AFTERNOON/EARLY EVENING. BOUTS OF
WIND DAMAGE/SEVERE HAIL WILL BE POSSIBLE NONETHELESS.
...MIDWEST...
IN SPITE OF AMPLE LARGE SCALE FORCING FOR ASCENT AND STRENGTHENING
DEEP LAYER WIND FIELDS...AN APPRECIABLE LOW LEVEL MOIST
INFLUX/SURFACE BASED DESTABILIZATION SEEMS UNLIKELY INTO THE MIDWEST
/INCLUDING MUCH OF IL AND INDIANA/ AHEAD OF THE COLD FRONT.
NONETHELESS...WEAK ELEVATED BUOYANCY/STRONG WIND FIELDS COULD
SUPPORT SOME MARGINALLY SEVERE HAIL AND/OR CONVECTIVELY ENHANCED
WIND GUSTS MAINLY UNTIL AROUND SUNSET.
...SOUTHWEST TX...
TSTMS MAY INCREASE LATE IN THE PERIOD ACROSS SOUTHWEST TX AS
MOISTURE SURGES WESTWARD INTO THE REGION IN VICINITY OF LOW LEVEL
BAROCLINIC ZONE. WEAK HEIGHT FALLS/STRONG SHEAR AND AMPLE ELEVATED
INSTABILITY MAY SUPPORT STORMS CAPABLE OF SEVERE HAIL LATER TONIGHT.
..GUYER/GARNER.. 10/06/2009
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