Post by Randy - Brandon, MS on Mar 18, 2008 19:47:06 GMT -6
bwhorton2007 said:
not sure about that as things are not that impressive and a huge cap in place too although some weak convection is firing west of me.I just noticed the latest update from Jackson NWS. They expect that cap to break down in a hurry in just a little while.
.DISCUSSION...THINGS ARE EVOLVING SLOWLY AT THIS POINT...BUT ARE
EXPECTED TO HAVE A MARKED INCREASE IN THE ACTION BETWEEN 8-9 PM TO
OUR WEST WITH THINGS EVOLVING QUICKLY THROUGH THE REMAINDER OF THE
EVENING AND ACCELERATING EASTWARD ACROSS MY FORECAST AREA BETWEEN
MIDNIGHT AND 7 AM.
DUE TO THE SLOW EVOLUTION UP TO THIS POINT...THE FORECAST HAS BEEN
ADJUSTED TO REFLECT THAT TIMING. AS FOR THE CONDITIONS
OUTSIDE...WINDS WILL REMAIN QUITE STRONG AHEAD OF THE SQUALL LINE AS
THE SFC LOW EDGES EVER CLOSER. ALOFT...WINDS WILL STEADILY INCREASE
IN ADVANCE OF THE SYSTEM...CREATING A STRONGLY SHEARED ENVIRONMENT
WITH 0-1 KM VALUES BETWEEN 45-50KTS. LOW LEVEL
HELICITIES...0-1KM...WILL ALSO BE OFF THE CHART WITH VALUES BETWEEN
400-600 M2/S2. STRONG ASCENT WILL APPROACH THE FORECAST AREA BY
10-11PM AND HELP TO REMOVE THE WARM MID LEVEL LAYER. THE RESULT WILL
BE A STRONGLY FORCED SQUALL LINE MOVING ACROSS THE AREA. AS THIS
LINE EVOLVES...BOWING SEGMENTS WILL BE COMMON AND POSE A SIG WIND
THREAT. SOME GUSTS IN THE SEGMENTS COULD EXCEED 80 MPH. ALSO...DUE
TO THE VERY HIGH LEVELS OF LOW LEVEL WIND SHEAR...THESE BOWING
SEGMENTS WILL POSE A DECENT TORNADO RISK. OFTEN TIMES...THESE BOWING
SEGMENTS IN SIMILAR VERY HIGH SHEAR ENVIRONMENTS ARE VERY EFFICIENT
AT PRODUCING TORNADOES. AS HAS BEEN THE CASE WITH ALL PREV FORECAST
FOR THIS EVENT...INSTABILITY WILL REMAIN ON THE LOW SIDE.
HOWEVER...GRIDDED MLCAPE VALUES FROM THE RUC OFFER 400-600 J/KG JUST
AHEAD OF THE LINE AND GFS BUFR SOUNDINGS SHOW 600-1000 J/KG OF
MLCAPE. THIS HAS BEEN VERY CONSISTENT AND MATCHES WELL WITH THE
OBSERVED 00Z RAOBS AT SHV/LCH. IF THAT TYPE OF INSTABILITY CAN
REMAIN AS THE STRONG FORCING ASSOCIATED WITH +90KTS AT 500MB AND
70-80KTS AT 700MB...THEN A NASTY LINE WITH BOWING SEGMENTS CAN BE
EXPECTED.
LATEST GRAPHICAST OUTLINES THE TIMING WITH AREAS ALONG AND W OF THE
MS RIVER SEEING ACTIVITY BETWEEN 10 PM AND 1 AM. THE I-55 CORRIDOR
BETWEEN 1-4 AM WHILE THE E 1/3 BETWEEN 4-7 AM.
