SWODY1
SPC AC 080606
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1206 AM CST TUE DEC 08 2009
VALID 081200Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE LOWER MS VALLEY/MID
SOUTH INTO CENTRAL GULF COAST STATES...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN CAROLINAS AND SERN
VA TONIGHT...
...SYNOPSIS...
MODELS REMAIN IN GOOD AGREEMENT WITH THE TRACK AND ORIENTATION OF
THE LOWER CO RIVER VALLEY/FOUR CORNERS SHORTWAVE TROUGH AS IT
BECOMES NEGATIVELY TILTED MOVING EWD TO KS/OK BY LATE THIS
AFTERNOON/EARLY EVENING. THIS SYSTEM WILL THEN PROGRESS NEWD
UNDERGOING A DEEPENING PROCESS AS IT TRACKS TOWARD THE MID MS/LOWER
OH VALLEY AND SWRN GREAT LAKES REGION.
AT THE SURFACE...PRIMARY CYCLONE IS FORECAST TO INITIALLY DEVELOP
ESEWD FROM SWRN CO TO ALONG THE OK/KS BORDER BY LATE AFTERNOON
BEFORE ACCELERATING AND DEEPENING NEWD INTO IL...REACHING NERN IL/
SRN LAKE MI BY 12Z WEDNESDAY. 08/00Z MODEL GUIDANCE REMAINS
CONSISTENT SHOWING THE MOST INTENSE DEEPENING OF THE SURFACE LOW
WILL OCCUR BETWEEN 09/06Z-09/12Z...WELL AWAY FROM EFFECTIVE WARM
SECTOR. THE PRIMARY FOCUS FOR STRONG TO SEVERE STORMS...SOME
PRODUCING SIGNIFICANT SEVERE OVER THE WRN SLIGHT RISK AREA...WILL BE
ALONG AND EAST OF A SW-NE ORIENTED DRY LINE/CONVERGENCE ZONE
EXTENDING FROM THE TX COAST INTO THE MID SOUTH. THIS BOUNDARY WILL
THEN MOVE EWD THROUGH MS/AL TUESDAY EVENING/NIGHT. MEANWHILE...
ANOTHER FOCUS FOR STRONG TO SEVERE STORMS WILL BE ALONG AND S OF A
WARM FRONT SPREADING NWD ACROSS THE LOWER MS VALLEY/CENTRAL GULF
COAST STATES...WITH THIS BOUNDARY EXTENDING FROM NRN MS SSEWD TO SRN
MS AND SWRN AL BY 09/00Z. THE ERN EXTENT OF THE WARM FRONT ANALYZED
AS A WEDGE FRONT SHOULD MOVE MORE SLOWLY NWD TODAY THROUGH GA AND
THE PIEDMONT AND COASTAL PLAINS OF THE CAROLINAS TO SERN VA.
...LOWER MS VALLEY/MID SOUTH TO WRN GA/WRN FL PANHANDLE...
THE INITIAL FOCUS FOR STRONG TO SEVERE STORMS SHOULD BE LOCATED
ALONG THE SRN EXTENT OF AN ONGOING MCS OVER SRN LA/SRN MS WITH THIS
ACTIVITY PERSISTING INTO THE AFTERNOON AND SPREADING EWD TUESDAY
EVENING. THIS WILL OCCUR AS LLJ VEERS TO SWLY AND STRENGTHENS
BENEATH INCREASING SWLY MID LEVEL WINDS ATTENDANT TO SRN EXTENT OF
STRONG /100+ KT/ MID LEVEL JET NOSING INTO THE OZARK REGION BY EARLY
EVENING...AND BOUNDARY LAYER DESTABILIZES WITH INTRUSION OF SURFACE
DEWPOINTS IN THE MID 60S TO NEAR 70. ALTHOUGH INSTABILITY WILL BE
WEAK...EFFECTIVE BULK SHEAR 35-40 KT AND 0-1 KM SRH 200-400 M2/S2
SUGGEST LIKELIHOOD FOR BOWS/EMBEDDED SUPERCELLS. FAST STORM MOTION
/40-50 KT/ COMBINED WITH ROTATING UPDRAFTS WILL SUPPORT THREATS FOR
TORNADOES SOME STRONG TO SIGNIFICANT AS WELL AS STRONG DAMAGING
WINDS.
ADDITIONAL TSTM DEVELOPMENT IS EXPECTED ALONG NRN EXTENT OF DRY LINE
TO WARM FRONT INTERSECTION OVER SERN AR/NWRN MS BY LATE AFTERNOON
WITH ACTIVITY SPREADING EWD ACROSS NRN/CENTRAL EXTENT OF MS/AL
TOWARD GA SECOND HALF OF FORECAST PERIOD. SWLY LOWER TROPOSPHERIC
WINDS WILL STRENGTHEN /850-700 MB FLOW TO 70 KT/ ACROSS NRN EXTENT
OF THIS SLIGHT RISK AREA IN RESPONSE TO STRONG HEIGHT FALLS
ATTENDANT TO DEEPENING UPPER TROUGH. THESE KINEMATICS WILL SUPPORT
BOTH A THREAT FOR DAMAGING WINDS AND A FEW STRONG TO SIGNIFICANT
TORNADOES FROM NERN LA/SERN AR ACROSS NRN/CENTRAL MS TO WRN AL WELL
INTO THE LATE EVENING/OVERNIGHT PERIOD.
...ERN CAROLINAS/SERN VA...
EWD MIGRATION/DEVELOPMENT OF SLY LLJ WILL RESULT IN AN INFLUX OF
MOISTURE OFF THE WRN ATLANTIC...AND EVENTUALLY ERN GULF OF MEXICO
BASIN IN WAKE OF RETREATING WEDGE FRONT. WHILE THE GREATER AIR MASS
DESTABILIZATION IS FORECAST TO REMAIN CONFINED TO THE VICINITY OF
THE GULF STREAM...IT DOES APPEAR THAT SUFFICIENT INSTABILITY MAY BE
PRESENT TO SUPPORT THE DEVELOPMENT OF ISOLATED/SCATTERED NOCTURNAL
STORMS WITHIN STRENGTHENING WAA REGIME. GIVEN THE STRONG...AMBIENT
VERTICAL SHEAR FORECAST /40-50 KT/...THE POTENTIAL WILL EXIST FOR A
SEVERE WEATHER THREAT ATTENDANT TO ANY SUSTAINED UPDRAFTS DEVELOPING
FROM ERN SC NNEWD TO SRN VA OVERNIGHT.
...LOWER OH AND TN VALLEYS...
STRONG LOW LEVEL WAA COMBINED WITH COLD MID LEVEL TEMPERATURES/
STEEP LAPSE RATES SPREADING ACROSS THIS REGION TUESDAY EVENING/
NIGHT WITHIN EXIT REGION OF A 100+ KT MID LEVEL JET NOSING INTO THIS
AREA SHOULD SUPPORT ELEVATED TSTMS. THE STEEP LAPSE RATES WITH
ACTIVITY ROOTED AROUND 850 MB AND EFFECTIVE BULK SHEAR 30-35 KT IS
EXPECTED TO SUPPORT AN ISOLATED THREAT FOR HAIL... POTENTIALLY UP TO
1 INCH. THIS ACTIVITY WILL DEVELOP EWD ACROSS SRN IND/KY/TN TUESDAY
NIGHT.
..PETERS.. 12/08/2009
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