SWODY3
SPC AC 020737
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0237 AM CDT SAT APR 02 2011
VALID 041200Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM E TX TO THE CENTRAL GULF
COAST STATES AND NWD THROUGH THE TN/OH VALLEYS...
...E TX TO CENTRAL GULF COAST STATES NWD TO TN/OH VALLEYS...
THE 00Z GFS IS NOW FASTER THAN THE 00Z ECMWF WITH THE PROGRESSION OF
THE CENTRAL PLAINS TROUGH ON MONDAY ACROSS AND E OF THE MS VALLEY
REGION. IN ADDITION TO THESE TIMING DIFFERENCES...THE GFS INDICATED
STRONGER FORCING FOR ASCENT ACROSS THE TN/OH VALLEYS...WHILE THE
ECMWF INDICATED STRONGEST FORCING FOR ASCENT SPREADING ACROSS THE
LOWER MS VALLEY/CENTRAL GULF COAST STATES MONDAY NIGHT WITH A MORE
SWD TRACKING SHORTWAVE TROUGH.
EACH MODEL SHOWED STRONG BAROCLINICITY AS A COLD FRONT ADVANCES EWD
ACROSS THE OH/TN AND LOWER MS VALLEYS...WITH THE GFS AGAIN FASTER
WITH EWD PROGRESSION SHOWING THE FRONT REACHING THE ERN SEABOARD BY
12Z TUESDAY. DESPITE THE AFOREMENTIONED DIFFERENCES BETWEEN THE GFS
AND ECMWF...THIS TROUGH WILL UNDERGO STRENGTHENING AS IT BECOMES
NEUTRALLY ORIENTED...SUPPORTING INCREASING SWLY MIDLEVEL WINDS
/60-80 KT/ FROM TX/LOWER MS VALLEY TO THE TN/OH VALLEYS...WITH
FURTHER STRENGTHENING /90-100 KT/ MONDAY NIGHT AS THE FLOW BACKS TO
SLY. IN THE LOW LEVELS...A 50-60 KT SSWLY LLJ FROM THE LOWER MS TO
LOWER OH VALLEYS WILL SUPPORT MOISTURE SPREADING NWD ACROSS THE WARM
SECTOR.
TSTMS WILL BE LIKELY AS THE COLD FRONT ENCOUNTERS THE DESTABILIZING
AIR MASS AND FORCING FOR ASCENT INCREASES WITH THE EWD PROGRESSION
OF THE MID-UPPER LEVEL TROUGH. THE GREATEST INSTABILITY IS EXPECTED
FROM THE TN VALLEY SWD. DEEP LAYER SHEAR VECTORS ORIENTED MAINLY
PARALLEL TO THE COLD FRONT SUGGEST A LINEAR STORM MODE WITH BOWING
SEGMENTS LIKELY. HOWEVER...THE STRENGTH OF THE BULK SHEAR /40-55
KT/ MAY SUPPORT EMBEDDED SUPERCELL STRUCTURES WITHIN THE QLCS.
ALTHOUGH INSTABILITY WILL TEND TO BE MARGINAL WITH NWD EXTENT...THE
STRENGTH OF THE DEEP LAYER AND LOW LEVEL SHEAR SHOULD OVERCOME THAT
LIMITING FACTOR AND SUPPORT MAINLY A DAMAGING WIND THREAT ACROSS THE
OH VALLEY.
IF THE ECMWF IS CORRECT...THEN THERE WILL BE A SEVERE WEATHER THREAT
INTO THE LATTER HALF OF THE FORECAST PERIOD FROM THE LOWER MS VALLEY
TO THE CENTRAL GULF COAST STATES.
..PETERS.. 04/02/2011
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