SWODY1
SPC AC 031242
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0742 AM CDT THU MAY 03 2007
VALID 031300Z - 041200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF SRN/ERN TX AND
LOWER MS RIVER VALLEY...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE NRN/CENTRAL
HIGH PLAINS...
..SRN/ERN TX ACROSS THE LOWER MS RIVER VALLEY...
SUPPRESSION OF RICH LOW LEVEL MOISTURE SWD INTO THE NWRN GULF OF
MEXICO FROM EXTENSIVE CONVECTION OVERNIGHT LIMITS CONFIDENCE ON HOW
SEVERE THREAT WILL PLAY-OUT ACROSS THIS REGION TODAY. SLOW MOVING
MID/UPPER LOW NOW OVER NRN TX IS EXPECTED TO OPEN UP AND SHIFT EWD
AS A NEGATIVELY TILTED TROUGH INTO THE LOWER MS RIVER VALLEY. AS
THIS OCCURS...POCKET OF RELATIVELY COOL MID LEVEL AIR /H5 TEMPS AOB
-12C/ WILL OVERSPREAD NRN/ERN TX WITH INCREASING SSWLY MID LEVEL
WINDS SHIFTING ACROSS LA.
LARGE BOW-ECHO MCS WHICH MATURED OVER DEEP SOUTH TX LAST NIGHT
APPEARS TO BE PERSISTING AS IT RACES ENEWD ACROSS THE WRN GULF OF
MEXICO EARLY THIS MORNING. NRN PORTION OF COMPOSITE SURFACE OUTFLOW
BOUNDARY WILL LIKELY CONTINUE WORKING ITS WAY EWD ACROSS CENTRAL LA
THIS MORNING. AS THIS OCCURS...COASTAL FRONT MAY PUSH SLOWLY INLAND
INTO SERN LA AND POSSIBLY FAR SRN MS BY THE EARLY AFTERNOON.
ISOLATED SEVERE THUNDERSTORMS MAY PRODUCE LARGE HAIL AND ISOLATED
DAMAGING WINDS THIS MORNING OVER SRN LA. HOWEVER...STORMS SHOULD
INCREASE IN COVERAGE AND INTENSITY AS THEY POSSIBLY BUILD UPWARDS
INTO A CLUSTER/LINE OF SEVERE STORMS THROUGH THE AFTERNOON AND MOVE
ENEWD ACROSS THE LOWER MS RIVER VALLEY.
AS MORNING MCS OVER THE WRN GULF SHIFTS ENEWD AND PERSISTENT HEIGHT
FALLS ALOFT SUSTAIN SLY LLJ OVER ERN TX...GRADUAL RETURN OF GULF
MOISTURE/COASTAL FRONT SHOULD OCCUR ACROSS SERN TX TODAY. AS THIS
BOUNDARY LIFTS NWD...AIR MASS WILL LIKELY BECOME VERY UNSTABLE DUE
TO COOL AIR ALOFT AND INFLUX OF EML OUT OF NERN MEXICO. DRT AND BRO
BOTH INDICATE 7+ C/KM MID LEVEL LAPSE RATES AT 12Z. INCREASED ASCENT
NEAR THE UPPER TROUGH SHOULD AID IN THUNDERSTORM DEVELOPMENT NEAR
NUMEROUS SURFACE BOUNDARIES LEFT FROM EARLIER CONVECTION OVER
SERN/E-CENTRAL TX. HOW FAR WSW DEVELOPMENT CAN OCCUR ALONG SURFACE
FRONT IS DISPUTED BY THE MODELS. HOWEVER GIVEN STRONG HEATING AND
ABUNDANT MOISTURE... STRONGLY UNSTABLE AND WEAKLY CAPPED AIR MASS
SHOULD DEVELOP. THIS WARRANTS EXTENSION OF SLGT RISK INTO S-CENTRAL
TX LATER TODAY DESPITE MORE ISOLATED STORM COVERAGE EXPECTED OVER
THIS AREA. MODEST WLY MID LEVEL WINDS WILL SHIFT TO NWLY THROUGH
THE EVENING OVER TX AND SUSTAIN SUFFICIENT SHEAR FOR SUPERCELLS AND
LINES/CLUSTERS OF SEVERE THUNDERSTORMS. ACTIVITY SHOULD SHIFT
GENERALLY EWD AND WEAKEN DURING THE MID TO LATE EVENING.
..CENTRAL/NRN HIGH PLAINS...
INTENSE...NEGATIVELY-TILTED UPPER TROUGH WILL REMAIN DOMINANT
FEATURE OVER THE WRN U.S. TODAY. AHEAD OF THIS SYSTEM...SURFACE LOW
NOW OVER CENTRAL WY IS FORECAST TO DEEPEN ALONG STRENGTHENING LEE
TROUGH/COLD FRONT WHICH WILL MOVE EWD INTO ERN MT/WY BY LATER TODAY.
NOSE OF 50+ KT MID LEVEL JET WILL ROUND BASE OF TROUGH AND EXTEND
INTO THE CENTRAL HIGH PLAINS BY LATER TODAY...WHILE MID LEVEL WINDS
REMAIN MORE SLY AS THEY SHIFT EWD OVER THE NRN HIGH PLAINS.
STRONG...DEEP ASCENT WILL ENHANCE CONVERGENCE AND INCREASING UPSLOPE
FLOW AHEAD OF THE SURFACE TROUGH/COLD FRONT AND SUPPORT THUNDERSTORM
DEVELOPMENT BY THE MID TO LATE AFTERNOON. HOWEVER...MORNING SURFACE
ANALYSES INDICATE LOW LEVEL MOISTURE REMAINS SCARCE OVER THE AREA
AND IMMEDIATELY UPSTREAM WITH RIDGE AXIS EXTENDING SSWWD ACROSS WRN
KS. THIS WILL LIMIT AVAILABLE MOISTURE/INSTABILITY THIS AFTERNOON.
REGARDLESS...FORECAST SOUNDINGS INDICATE STEEP LAPSE RATES AND AN
AXIS OF MARGINAL INSTABILITY...ALONG WITH SUFFICIENT SHEAR FOR
SUPERCELLS. THIS SHOULD ENHANCE THE POTENTIAL FOR LARGE HAIL AND
POSSIBLY ISOLATED DAMAGING WINDS THROUGH THE EARLY TO MID EVENING AS
ACTIVITY CONSOLIDATES INTO ONE OR MORE MCSS. ISOLATED TORNADOES MAY
ALSO OCCUR...ESPECIALLY WITH DEVELOPMENT INTO ERN/NERN CO ALONG NOSE
OF STRONGER WLY MID LEVEL FLOW. SEVERE THREAT SHOULD DIMINISH
OVERNIGHT AS ACTIVITY SPREADS EAST OF INSTABILITY AXIS OVER THE WRN
DAKOTAS/WRN-CENTRAL NEB.
.EVANS/TAYLOR.. 05/03/2007
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