SPC AC 230556
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1156 PM CST TUE DEC 22 2009
VALID 241200Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER MS
VALLEY AND ERN GULF COAST STATES...
...LOWER MS VALLEY/ERN GULF COAST STATES...
A HIGHLY MERIDIONAL UPPER-LEVEL TROUGH WILL BECOME NEGATIVELY TILTED
THURSDAY MORNING AS A STRONG COLD FRONT MOVES INTO THE LOWER MS
VALLEY FROM THE WEST. AHEAD OF THE FRONT AND ALONG THE LEADING EDGE
OF LARGE-SCALE ASCENT...A LARGE CONVECTIVE BAND SHOULD BE ONGOING
THURSDAY MORNING FROM NEAR SHREVEPORT SWD TO NEAR BATON ROUGE LA.
ETA-KF FORECAST SOUNDINGS AT 12Z ALONG AND AHEAD OF THIS CORRIDOR
THURSDAY SHOW 0-6 KM SHEAR VALUES OF 45 TO 55 KT WITH UNIDIRECTIONAL
WIND PROFILES ALONG THE BOUNDARY SUGGESTING A SQUALL-LINE WILL BE
ONGOING THURSDAY MORNING. EAST OF THE SQUALL-LINE ACROSS CNTRL AND
ERN LA...FORECAST SOUNDINGS SHOW AN IMPRESSIVE LOW-LEVEL SHEAR
ENVIRONMENT WITH SUBSTANTIAL BOUNDARY LAYER SPEED SHEAR AND STRONGLY
CURVED HODOGRAPHS. THIS SHOULD BE FAVORABLE FOR DISCRETE ROTATING
STORMS WITH A POTENTIAL FOR TORNADOES AHEAD OF THE SQUALL-LINE. THE
MODELS ARE IN GOOD AGREEMENT...MOVING THE SQUALL-LINE QUICKLY EWD
INTO INCREASING INSTABILITY ACROSS SE LA AND SRN MS MAINTAINING THE
WIND DAMAGE THREAT THROUGH THURSDAY AFTERNOON. TORNADOES WILL ALSO
BE POSSIBLE ESPECIALLY WITH DISCRETE CELLS EWD INTO THE NEW ORLEANS
LA AND BILOXI MS AREAS ON THE WRN EDGE OF A STRONG LOW-LEVEL JET.
FOR THURSDAY EVENING INTO THE OVERNIGHT PERIOD...THE GFS/NAM/ECMWF
MODEL SOLUTIONS VARY SOME WITH THE SPEED OF THE FRONT. A CONSENSUS
AMONG THE MODELS PLACE THE SQUALL-LINE IN ERN AL AND THE WRN FL
PANHANDLE BY 06Z REACHING WRN AND CNTRL GA LATE IN THE PERIOD. THE
STRONGER ELEMENTS IN THE SQUALL-LINE AND DISCRETE STORMS AHEAD OF
THE LINE SHOULD MAINTAIN A WIND DAMAGE AND TORNADO THREAT OVERNIGHT.
HOWEVER...THE STRONGER WINDS WITH THE LOW-LEVEL JET ARE FORECAST TO
BE MOVING NNEWD AWAY FROM THE GULF COAST THURSDAY NIGHT SUGGESTING
SEVERE THREAT COVERAGE MAY DECREASE SOMEWHAT.
..BROYLES.. 12/23/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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