
SPC AC 180600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT TUE MAR 18 2008
VALID 181200Z - 191200Z
...THERE IS A MDT RISK OF SVR TSTMS FROM ERN TX...SRN AR AND NRN
THROUGH WRN LA...
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN TX INTO THE LOWER
MS...TN AND SRN OH VALLEYS...
...SYNOPSIS...
SPLIT FLOW PROGRESSIVE PATTERN WILL REMAIN THROUGH TUESDAY. NRN
STREAM UPPER TROUGH WILL MOVE EWD THROUGH THE UPPER MS VALLEY AND
INTO THE GREAT LAKES REGION...WHILE SRN STREAM CUTOFF LOW EJECTS
NEWD THROUGH ERN TX AND THE LOWER MS VALLEY. SW-NE ORIENTED
BAROCLINIC ZONE FROM SWRN TX NEWD INTO SRN MO AND THE OH VALLEY
EARLY TUESDAY WILL SHIFT SLOWLY SEWD DURING THE DAY...WHILE FRONT
ACCOMPANYING THE SRN STREAM UPPER LOW WILL ADVANCE THROUGH SERN
TX...REACHING THE LOWER MS VALLEY TUESDAY NIGHT.
...ERN TX THROUGH THE LOWER MS VALLEY REGION...
WIDESPREAD CONVECTION WILL LIKELY BE ONGOING AT THE START OF THE
PERIOD FROM PARTS OF W CNTRL TX NEWD THROUGH OK AND THE MID MS
VALLEY REGION. SOME HAIL WILL REMAIN POSSIBLE...MAINLY WITH ACTIVITY
OVER TX WHERE STEEPER LAPSE RATES AND STRONGER INSTABILITY WILL
EXIST. RICH LOW LEVEL MOISTURE RESIDES IN WARM SECTOR ACROSS ERN TX
AND THE LOWER MS VALLEY WITH
DEWPOINTS IN THE UPPER 60S TO AROUND
70. AS THE BOUNDARY LAYER WARMS THE ATMOSPHERE WILL BECOME
MODERATELY UNSTABLE. SLY TRAJECTORIES AND MID LEVEL THERMAL RIDGE
DOWNSTREAM FROM UPPER TROUGH WILL RESULT IN ONLY MODEST 700-500 MB
LAPSE RATES. HOWEVER...WARMING OF THE BOUNDARY LAYER WILL CONTRIBUTE
TO
1500 J/KG MLCAPE DURING THE DAY. STORMS ARE EXPECTED TO REDEVELOP
ACROSS PARTS OF SERN AND ERN TX IN VICINITY OF EWD ADVANCING FRONT
AND WITHIN DIVERGENT EXIT REGION OF MID LEVEL JET. FORECAST VERTICAL
WIND PROFILES SHOW STRONG LOW LEVEL SHEAR ALONG THE 50+ KT LOW LEVEL
JET AXIS...BUT EXHIBIT A VEER-BACK PATTERN IN THE 850-700 MB LAYER.
THIS PROFILE WILL LIKELY SUPPORT AN EVOLUTION TO MIXED STORM MODES
INCLUDING LINES WITH EMBEDDED SUPERCELLS THAT WILL MOVE THROUGH ERN
TX AND THE LOWER MS VALLEY REGION. DAMAGING WIND AND A FEW TORNADOES
WILL BE POSSIBLE WITH GREATEST THREAT EXPECTED IN MODERATE RISK
AREA. DESPITE WEAKENING INSTABILITY...STRONG LINEAR FORCING WILL
LIKELY MAINTAIN LINES OF STORMS THROUGH THE LOWER MS VALLEY AND INTO
A PORTION OF THE SERN STATES OVERNIGHT.
...MID MS AND TN VALLEY THROUGH SRN PARTS OF THE OH VALLEY...
DESPITE AN AXIS OF LOWER 60S DEWPOINTS ADVECTING NEWD ALONG THE
SW-NE BAROCLINIC ZONE...INSTABILITY WILL REMAIN WEAK IN THIS REGION
OWING TO EXPECTED WIDESPREAD CLOUDS AND MODEST MID LEVEL LAPSE
RATES. HOWEVER...POTENTIAL WILL EXIST FOR ORGANIZED STORM STRUCTURES
ALONG THE SW-NE ORIENTED BOUNDARY AS WITHIN ZONE OF FORCING
ASSOCIATED WITH NEWD MIGRATING LOW LEVEL JET AND SURFACE LOW.
VERTICAL WIND PROFILES WILL SUPPORT ORGANIZED STORM STRUCTURES
INCLUDING POTENTIAL FOR SUPERCELLS AND BOW ECHOES. ISOLATED DAMAGING
WIND AND TORNADOES WILL BE POSSIBLE. THE THREAT APPEARS SOMEWHAT
MORE MARGINAL TOWARD THE TN AND OH VALLEY WHERE INSTABILITY WILL BE
MORE LIMITED.
..DIAL/JEWELL.. 03/18/2008
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