SWODY1
SPC AC 071935
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0235 PM CDT TUE OCT 07 2008
VALID 072000Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS THRU MID EVE ACROSS UPPER
PORTIONS OF THE LOWER MISSISSIPPI VALLEY....
...LOWER MISSISSIPPI VALLEY/EASTERN GULF STATES...
LOW-LEVEL COOLING ASSOCIATED WITH THE NORTHERN BRANCH SHORT WAVE
IMPULSE IS NOW SURGING INTO THE OZARK PLATEAU REGION...MERGING WITH
THE WEAK LEAD FRONT/WIND SHIFT ASSOCIATED WITH THE SOUTHERN STREAM.
AND...AN AMPLIFICATION OF THE SOUTHERN STREAM IMPULSE IS WELL
UNDERWAY ACROSS EASTERN KANSAS/OKLAHOMA INTO NORTHEAST TEXAS. THIS
FEATURE IS PROGGED TO GRADUALLY TURN EASTWARD TOWARD THE LOWER
MISSISSIPPI VALLEY THROUGH EARLY EVENING...AND MAY SUPPORT A FURTHER
INCREASE IN UPWARD VERTICAL MOTIONS AND STRENGTHENING OF SOUTHERLY
LOW-LEVEL FLOW FIELDS FROM NEAR THE ARKANSAS/MISSISSIPPI BORDER AREA
INTO THE CONFLUENCE OF THE OHIO/MISSISSIPPI RIVERS.
VIGOROUS CONVECTIVE DEVELOPMENT IS ONGOING NEAR THIS CORRIDOR...
WHERE AN AXIS OF STRONGER HEATING HAS BECOME COINCIDENT WITH A LOW
LEVEL MOIST AXIS...SOUTH/SOUTHEAST OF ELONGATED SURFACE LOW CENTER
OVER CENTRAL MISSOURI. RUC GUIDANCE INDICATES MIXED LAYER COULD
STILL INCREASE TO IN EXCESS OF 1000 J/KG...AND IT IS BECOMING MORE
CERTAIN THAT A WINDOW OF OPPORTUNITY MAY EXIST FOR A FOCUSED ZONE OF
STRONG/SEVERE THUNDERSTORM DEVELOPMENT THROUGH THE 02-03Z TIME
FRAME.
THIS HAS BEEN A POINT OF UNCERTAINTY DUE TO THE WEAKNESS OF THE
SURFACE CYCLOGENESIS...AND THE SLOW RATE AT WHICH LOW/MID-LEVEL
RIDGING...EXTENDING FROM THE EASTERN STATES THROUGH HUDSON
BAY...BREAKS DOWN/RETREATS IN ADVANCE OF A STRONG MID/UPPER JET
STREAK NOW NOSING SOUTH OF THE INTERNATIONAL BORDER AREA TOWARD THE
UPPER MISSISSIPPI VALLEY. THIS STILL APPEARS LIKELY TO CONFINE WARM
SECTOR BOUNDARY LAYER BASED INSTABILITY TO A NARROWING WEDGE ACROSS
THE EAST CENTRAL GULF COAST STATES AND LOWER MISSISSIPPI VALLEY.
AND...A CONSOLIDATING STORM CLUSTER NEAR THE INTERSECTION OF THE
SOUTHERN STREAM FRONT AND A NORTHERN GULF OF MEXICO LOW-LEVEL
CONFLUENCE ZONE PROBABLY WILL INHIBIT A CONTINUING INLAND RETURN
FLOW OF MOISTURE. COUPLED WITH THE ONSET OF WARM SECTOR BOUNDARY
LAYER COOLING/STABILIZATION AFTER SUNSET...THE SEVERE THREAT
EASTWARD INTO THE EASTERN GULF COAST STATES AND TENNESSEE VALLEY IS
EXPECTED TO REMAIN LOW TONIGHT.
HOWEVER...UNTIL MID EVENING...INSTABILITY AND MODERATELY STRONG DEEP
LAYER SHEAR BENEATH 40 KT SOUTHWESTERLY 500 MB FLOW MAY PROMOTE A
FEW SEVERE STORMS ACROSS PARTS OF EASTERN ARKANSAS... NORTHWEST
MISSISSIPPI AND WESTERN TENNESSEE INTO THE MISSOURI
BOOTHEEL...PERHAPS PARTS OF EXTREME WESTERN KENTUCKY. ISOLATED
SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL/DAMAGING WIND GUSTS ARE
POSSIBLE...AND A RISK FOR TORNADOES COULD BRIEFLY DEVELOP BEFORE
STORMS WEAKEN...AS LOW-LEVEL HODOGRAPHS ENLARGE A BIT EARLY THIS
EVENING.
..KERR.. 10/07/2008
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