SWODY1
SPC AC 290031
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0631 PM CST FRI NOV 28 2008
VALID 290100Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS TONIGHT INLAND OF THE GULF
COAST...ACROSS PARTS OF THE LWR MS VALLEY....
...CENTRAL GULF COAST/LOWER MISSISSIPPI VALLEY...
A STRONG SOUTHERN BRANCH OF SPLIT POLAR WESTERLIES IS PRESENT
SOUTHEAST OF A REMNANT UPPER TROUGH AXIS EMANATING FROM THE SOUTHERN
PLATEAU...THROUGH TEXAS AND MUCH OF THE GULF STATES. NEAR AN
ASSOCIATED FRONTAL ZONE INLAND OF THE TEXAS COASTAL PLAIN THROUGH
PARTS OF CENTRAL LOUISIANA/MISSISSIPPI AND ALABAMA...FLOW ALOFT
STILL APPEARS BROADLY ANTICYCLONIC. BUT...THIS IS EXPECTED TO
TRANSITION TOWARD A BROADLY CYCLONIC REGIME WITH THE ONSET OF
GRADUAL MID-LEVEL HEIGHT FALLS TONIGHT...AS A SHORT WAVE IMPULSE
ACCELERATES EAST NORTHEAST OF THE SOUTH CENTRAL PLAINS THROUGH THE
OZARK PLATEAU. WHILE STRONGEST UPPER FORCING LIKELY WILL REMAIN
WELL TO THE NORTHWEST OF THE FRONTAL ZONE...MODELS INDICATE THAT A
WEAK FRONTAL WAVE MAY BEGIN TO SLOWLY DEEPEN LATER TONIGHT ACROSS
CENTRAL LOUISIANA INTO SOUTH CENTRAL MISSISSIPPI. THIS IS FORECAST
TO BE ACCOMPANIED BY AT LEAST MODEST STRENGTHENING OF SOUTHWESTERLY
850 MB FLOW...PERHAPS IN EXCESS OF 40 KT...WHICH WOULD ENHANCE THE
RISK FOR LOW-LEVEL MESOCYCLONE FORMATION WITHIN AN ENVIRONMENT WITH
STRONG DEEP LAYER SHEAR SUPPORTIVE OF SUPERCELLS.
THE THERMODYNAMIC ENVIRONMENT CONTINUES TO BE A LIMITING FACTOR WITH
REGARD TO THE SEVERE POTENTIAL. BUT...THE AIR MASS ALONG/SOUTH OF
THE FRONTAL ZONE HAS BECOME SEASONABLY MOIST...WITH AT LEAST WEAK
CONDITIONAL INSTABILITY BASED NEAR THE SURFACE...OR JUST ABOVE A
SHALLOW NEUTRAL TO STABLE SURFACE LAYER. THUS...THE RISK FOR
ISOLATED TORNADOES REMAINS NON NEGLIGIBLE THIS EVENING IN ONGOING
STORMS NEAR AN OUTFLOW BOUNDARY ACROSS EAST CENTRAL LOUISIANA INTO
SOUTHERN MISSISSIPPI. AND...THIS POTENTIAL COULD INCREASE AT LEAST
A BIT FURTHER LATER TONIGHT...AS THE SURFACE LOW EVOLVES...PROBABLY
NEAR THE OUTFLOW BOUNDARY/SURFACE FRONT INTERSECTION SHIFTING EAST
NORTHEASTWARD OUT OF CENTRAL LOUISIANA.
..KERR.. 11/29/2008
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