SWODY2
SPC AC 171730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT MON MAR 17 2008
VALID 181200Z - 191200Z
..THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF THE TX COASTAL
PLAIN AND SE TX...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN PLAINS
AND LOWER TO MID MS VALLEY...
..SRN PLAINS/LOWER MS VALLEY...
AN UPPER-LEVEL LOW OVER NRN MEXICO IS FORECAST TO MOVE SLOWLY EWD
INTO THE RIO GRAND VALLEY AND ACCELERATE NEWD TUESDAY EVENING AS A
BROAD LOW-LEVEL JET REMAINS IN PLACE ACROSS THE OZARKS AND MS
VALLEY. NUMEROUS THUNDERSTORMS SHOULD BE ONGOING AT THE BEGINNING OF
THE PERIOD ALONG THE WRN EDGE OF THE LOW-LEVEL JET FROM ECNTRL TX
EXTENDING NEWD INTO THE MID-MS VALLEY. THIS THUNDERSTORM ACTIVITY
SHOULD GRADUALLY SHIFT EWD ACROSS THE REGION AS A COLD FRONT
ADVANCES SEWD ACROSS SERN MO...NRN AR AND EAST TX TUESDAY. SEVERAL
CONVECTIVE CLUSTERS SHOULD DEVELOP BY TUESDAY EVENING MOVING ACROSS
THE MID-MS VALLEY OVERNIGHT AND INTO THE TN VALLEY LATE IN THE
PERIOD.
CONCERNING THE SHEAR ENVIRONMENT...AN IMPRESSIVE 90 TO 100 KT
MID-LEVEL JET ASSOCIATED WITH THE UPPER-LEVEL LOW IS FORECAST TO
MOVE ENEWD OUT OF THE BASE OF THE TROUGH CREATING STRONG VERTICAL
SHEAR PROFILES ACROSS THE SLIGHT RISK AREA. THIS WILL RESULT IN
FAVORABLE SHEAR FOR NUMEROUS SEVERE STORMS INCLUDING SUPERCELLS AND
BOW ECHOES. A SIGNIFICANT SEVERE WEATHER EVENT APPEARS LIKELY ACROSS
THE REGION. THE SEVERE THREAT SHOULD BE ONGOING AT THE START OF THE
PERIOD WITH A LARGE MCS ALONG THE I-35 CORRIDOR FROM CNTRL TX
EXTENDING NEWD TO NEAR SPRINGFIELD MO. A MORE SUBSTANTIAL SEVERE
THREAT SHOULD ALSO EXIST IN EAST TX AND ALONG THE TX COASTAL PLAINS
LATE TUESDAY MORNING AS A WELL-FOCUSED LOW-LEVEL JET MOVES NWD INTO
THE SABINE RIVER VALLEY. FORECAST SOUNDINGS AT 15Z TO 18Z TUESDAY
ACROSS THIS HOUSTON AREA SHOW 0-3 KM STORM RELATIVE HELICITY OF 400
TO 500 M2/S2 WHICH WILL BE FAVORABLE FOR TORNADOES ALONG THE WRN
EDGE OF THE LOW-LEVEL JET ACROSS SE TX EXTENDING NEWD TO NEAR THE
SABINE RIVER. A FEW STRONG TORNADOES WILL BE POSSIBLE WITH THE MORE
PERSISTENT SUPERCELLS WITH ACCESS TO LOCALLY GREATER INSTABILITY.
THE TORNADO THREAT APPEARS LIKELY TO PERSIST INTO THE AFTERNOON AS
INSTABILITY INCREASES AHEAD OF THE COLD FRONT AND NEW CELLS INITIATE
FURTHER EAST. STEEP MID-LEVEL LAPSE RATES OF 7 TO 7.5 C/KM SUGGEST
LARGE HAIL WILL BE LIKELY WITH SUPERCELLS. THE STRONG LOW-LEVEL FLOW
AND HIGH MOISTURE CONTENT IN THE BOUNDARY LAYER SHOULD ALSO SUPPORT
A WIND DAMAGE THREAT WITH SUPERCELLS...BOW ECHOES AND ORGANIZED LINE
SEGMENTS. A SEVERE THREAT SHOULD PERSIST INTO THE EVENING AS A
SQUALL-LINE ORGANIZES AND MOVES INTO LOWER AND MID MS VALLEY ALONG
THE LEADING EDGE OF ASCENT. THE WIND DAMAGE THREAT COULD BECOME
ENHANCED WITH A POTENTIAL FOR VERY STRONG WIND GUSTS TUESDAY EVENING
ACROSS LA AND WRN MS. THE MODERATE RISK AREA MAY NEED TO BE EXPANDED
ENEWD INTO THE LOWER MS VALLEY ONCE THE EXTENT OF THE WIND DAMAGE
THREAT BECOMES MORE CERTAIN.
.BROYLES.. 03/17/2008
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