SWODY2
SPC AC 130559
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1159 PM CST THU FEB 12 2009
VALID 141200Z - 151200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PROGRESSIVE ZONAL UPPER FLOW REGIME WILL CONTINUE THROUGH SATURDAY.
INITIAL SHORTWAVE TROUGH NOW MOVING THROUGH THE CNTRL ROCKIES WILL
DEAMPLIFY AS IT MOVES INTO THE OH VALLEY BY LATE FRIDAY. MODEL
CONSENSUS IS THAT UPSTREAM TROUGH CURRENTLY DIGGING SWD ALONG THE
PACIFIC NW COAST WILL EJECT EAST REACHING THE CNTRL PLAINS SATURDAY
NIGHT. A COLD FRONT WILL SURGE SWD THROUGH THE PLAINS AND OH VALLEY
IN WAKE OF LEAD IMPULSE. BY EARLY FRIDAY THIS BOUNDARY IS FORECAST
TO EXTEND FROM OH VALLEY SWWD THROUGH SRN TX. WRN PORTIONS OF FRONT
WILL LIKELY STALL ALONG THE WRN GULF COASTAL AREA WITHIN ZONE OF
INCREASING SLY FLOW AHEAD OF APPROACHING SHORTWAVE TROUGH. A COASTAL
BOUNDARY WILL HAVE MOVED INLAND ALONG THE SRN PORTIONS OF THE GULF
COASTAL STATES.
...S CNTRL THROUGH SE TX AND THE LOWER MS VALLEY...
SLY LOW LEVEL JET WILL STRENGTHEN ACROSS TX AND THE LOWER MS VALLEY
SATURDAY EVENING IN ADVANCE OF APPROACHING UPPER TROUGH THAT WILL
MOVE THROUGH THE SRN AND CNTRL PLAINS WELL NORTH OF THE FRONTAL
BOUNDARY. THETA-E ADVECTION AND LIFT ABOVE THE SHALLOW SURFACE FRONT
WILL CONTRIBUTE TO ELEVATED INSTABILITY GIVEN PRESENCE OF STEEP MID
LEVEL LAPSE RATES AND COLD MID LEVEL TEMPERATURES. THE ATMOSPHERE
WILL PROBABLY REMAIN CAPPED DURING THE DAY OVER TX.
HOWEVER...INCREASING ISENTROPIC ASCENT MAY BECOME SUFFICIENT TO
WEAKEN THE INVERSION AND BRING PARCELS TO THEIR LFCS DURING THE
EVENING OR OVERNIGHT FROM ERN TX INTO THE LOWER MS VALLEY. POTENTIAL
WILL EXIST FOR ELEVATED SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL.
THIS AREA WILL BE MONITORED FOR A POSSIBLE UPGRADE TO SLIGHT RISK IN
LATER OUTLOOKS.
...SRN PORTIONS OF CNTRL AND ERN GULF COASTAL STATES...
SCATTERED THUNDERSTORMS WILL BE ONGOING EARLY SATURDAY ALONG THE
GULF COASTAL REGION WITHIN ZONE OF MODEST LOW LEVEL THETA-E
ADVECTION AND ISENTROPIC ASCENT ASSOCIATED WITH MOIST WSWLY LOW
LEVEL JET. THIS FEATURE IS FORECAST TO VEER AND SHIFT EAST DURING
THE DAY WITH A GRADUAL DECREASE IN LOW LEVEL FORCING. STORMS WILL
EXIST IN AN ENVIRONMENT CHARACTERIZED BY MODEST INSTABILITY AND
30-40 KT UNIDIRECTIONAL DEEP LAYER FLOW AND SUFFICIENT BULK SHEAR
FOR SPLITTING UPDRAFTS AND BOWING SEGMENTS. THE STRONGER STORMS MAY
BE CAPABLE OF PRODUCING ISOLATED STRONG WIND GUSTS AND HAIL. INITIAL
ACTIVITY WILL LIKELY BE SLIGHTLY ELEVATED...AND BOUNDARY LAYER
WARMING SHOULD BE SLOW DUE TO EXPECTED WIDESPREAD CLOUDS. THIS ALONG
WITH TENDENCY FOR THE LOW LEVEL JET TO DECREASE WITH TIME LOWERS
CONFIDENCE IN AN ORGANIZED SEVERE THREAT.
..DIAL.. 02/13/2009
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