SWODY1
SPC AC 121940
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0240 PM CDT THU APR 12 2007
VALID 122000Z - 131200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF WEST TX...SW
OK...NE NM...FAR SE CO AND FAR SW KS...
..WRN PART OF THE SRN PLAINS...
WATER VAPOR IMAGERY CURRENTLY SHOWS AN UPPER-LEVEL TROUGH DIGGING
SEWD OVER SRN CA. THIS FEATURE WILL BEGIN TO MOVE ESEWD INTO AZ BY
EARLY THIS EVENING WITH A LARGE AREA OF DIFFLUENCE UPSTREAM FROM THE
TROUGH OVER ERN NM AND WEST TX. IN RESPONSE TO THE APPROACHING
UPPER-LEVEL TROUGH...A LOW-LEVEL JET WILL STRENGTHEN ACROSS THE SRN
PLAINS THIS EVENING. THIS WILL ADVECT LOW-LEVEL MOISTURE NWD ACROSS
WEST TX WITH INSTABILITY INCREASING ALONG THE MOIST AXIS. ISOLATED
TO SCATTERED THUNDERSTORM ACTIVITY SHOULD DEVELOP ALONG THE LEADING
EDGE OF ASCENT AS A SHORTWAVE TROUGH EJECTS EWD ACROSS WEST TX THIS
EVENING AHEAD OF THE MAIN UPPER-LEVEL TROUGH.
FORECAST SOUNDINGS IN THE LUBBOCK AREA AND ALONG THE MOIST AXIS
EARLY THIS EVENING SHOW VERTICAL SHEAR EXCEEDING 60 KT SUGGESTING
SUPERCELLS WILL BE POSSIBLE UPON INITIATION. THE SUPERCELL THREAT
MAY INCREASE BY LATE EVENING AS AN AREA OF MODERATE INSTABILITY
DEVELOPS. MODEL FORECASTS SHOW VERY STEEP LAPSE RATES EXCEEDING 9.0
C/KM ALONG THE WRN EDGE OF THE SLIGHT RISK SUGGESTING LARGE HAIL
WILL BE LIKELY WITH THE STRONGER THUNDERSTORMS. THE GREATEST WIND
DAMAGE THREAT SHOULD BE CONFINED TO FAR NE NM AND WEST TX WHERE
LOW-LEVEL LAPSE RATES WILL BE THE STEEPEST. STRONG THUNDERSTORMS
WILL LIKELY SPREAD EWD FROM THE CAPROCK INTO THE LOW-ROLLING PLAINS
AND SW OK OVERNIGHT AS A BAND OF LARGE-SCALE ASCENT ASSOCIATED WITH
THE LEAD SHORTWAVE TROUGH EJECTS NEWD ACROSS THE REGION.
..NEW ENGLAND/MID-ATLANTIC...
WATER VAPOR IMAGERY CURRENTLY SHOWS A LARGE UPPER-LOW OVER THE GREAT
LAKES WITH SEVERAL SUBTLE SHORTWAVE TROUGHS ROUNDING THE BASE OF THE
TROUGH ACROSS THE NERN STATES. THE FIRST SHORTWAVE TROUGH IS MOVING
ACROSS NEW ENGLAND WHERE CONVECTION IS ONGOING. ALTHOUGH INSTABILITY
IS WEAK...FORECAST SOUNDINGS SHOW 0-1 KM SHEAR VALUES EXCEEDING 50
KT THIS AFTERNOON ACROSS SRN NEW ENGLAND. THIS SHOULD BE ENOUGH FOR
ISOLATED MARGINALLY SEVERE WIND GUSTS WITH THE STRONGER CONVECTION
OVER THE NEXT FEW HOURS.
FURTHER SOUTHWEST ACROSS THE MID-ATLANTIC STATES...A POCKET OF
INSTABILITY CURRENTLY EXISTS SHOWN ON OBJECTIVE ANALYSIS. FORECAST
SOUNDINGS IN THIS AREA THIS AFTERNOON SHOW LOW-LEVEL LAPSE RATES
EXCEEDING 8.0 C/KM WITH UNIDIRECTIONAL LOW-LEVEL WINDS INCREASING
FROM AROUND 10 KT AT THE SFC TO 35 KT AT 850 MB. THIS MAY BE ENOUGH
FOR A MARGINAL WIND DAMAGE THREAT AS THUNDERSTORMS MOVE EWD OUT OF
THE HIGHER TERRAIN ONTO THE COASTAL PLAINS LATE THIS AFTERNOON.
.BROYLES.. 04/12/2007
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