SWODY2
SPC AC 030556
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT SUN APR 03 2011
VALID 041200Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS EXTENDING FROM E TX TO CENTRAL
GULF COAST STATES AND NWD TO THE OH VALLEY...
...SYNOPSIS...
THE 02/12Z ECMWF IS CONSISTENT WITH ITS 02/00Z RUN...AND REMAINS THE
SLOWEST AND FARTHEST SOUTH OF THE OPERATIONAL AND LATEST 21Z SREF
500 MB MEAN HEIGHTS...SHOWING THE BASAL SHORTWAVE TROUGH MOVING INTO
THE LOWER MS VALLEY DURING THE LATTER HALF OF DAY 2. HOWEVER...EVEN
WITH THE SLOWER ECMWF SOLUTION...60-100 METER HEIGHT FALLS ARE
EXPECTED IN ADVANCE OF THE PROGRESSIVE FULL LATITUDE TROUGH FROM THE
OH VALLEY TO MID SOUTH/LOWER MS VALLEY SUPPORTING STRONG DEEP LAYER
SSWLY WIND FIELDS. THE 03/00Z GFS COMPARED TO THIS MODEL RUN FROM
02/00Z IS NOW INDICATING STRONGER FORCING FOR ASCENT INTO THE MID
SOUTH BY MONDAY AFTERNOON.
IN THE LOW LEVELS...THE LATEST GFS CONTINUES TO INDICATE STRONGER
DEEPENING OF THE SURFACE LOW...WITH BOTH THE 00Z GFS/12Z ECMWF
TRACKING THE LOW FROM THE CENTRAL GREAT LAKES TO QUEBEC. EACH MODEL
CONTINUES TO SHOW STRONG BAROCLINICITY AS A COLD FRONT ADVANCES EWD
ACROSS THE OH/TN AND LOWER MS VALLEYS AND CENTRAL GULF COAST STATES.
THE ECMWF REMAINS THE SLOWER MODEL WITH EWD PROGRESSION OF THE COLD
FRONT...AND IN AGREEMENT WITH HPC MODEL DIAGNOSTICS HAVE KEPT SERN
EXTENT OF THE SLIGHT RISK IN LINE WITH THE ECMWF TIMING OF THE COLD
FRONT INTO GA BY 12Z TUESDAY.
...E TX TO CENTRAL GULF COAST STATES NWD TO TN/OH VALLEYS...
GREATEST SEVERE WEATHER THREAT AREA /COVERAGE AND INTENSITY/...
INCLUDING POTENTIAL FOR TORNADOES...DAMAGING WINDS AND HAIL IS
EXPECTED TO BE ACROSS THE LOWER MS/TN VALLEYS.
DESPITE THE MODEL DIFFERENCES DISCUSSED IN THE SYNOPSIS...EVEN 60-90
METER HEIGHT FALLS PER ECMWF FROM THE OH VALLEY TO THE MID
SOUTH/LOWER MS VALLEY AND MID-UPPER LEVEL TROUGH BECOMING NEUTRALLY
ORIENTED WILL SUPPORT FORCING FOR ASCENT SPREADING EWD ATOP THE COLD
FRONT AND ADJACENT WARM SECTOR. STEEP MIDLEVEL LAPSE RATES /8-9 C
PER KM/ ACROSS THE SLIGHT RISK AREA AT 12Z MONDAY WILL INITIALLY CAP
THE AIR MASS. HOWEVER...THE HEIGHT FALLS ARE EXPECTED TO ELIMINATE
THE CAP EARLY IN THE PERIOD /MONDAY MORNING/. FORCING ATTENDANT TO
THE TROUGH SHOULD MAINTAIN ONGOING TSTMS ALONG THE FRONT WHICH WILL
EXTEND FROM LOWER MI SWWD TO NERN AND CENTRAL TX...WHILE NEW STORMS
WILL ALSO DEVELOP AS THE CAP WEAKENS FROM W-E MONDAY MORNING INTO
THE AFTERNOON.
SLY LOW LEVEL WINDS WILL SPREAD MOISTURE NWD IN ADVANCE OF THE COLD
FRONT...WITH SURFACE DEWPOINTS IN THE LOWER 60S SPREADING ACROSS THE
OH VALLEY...AND MID-UPPER 60S SWD FROM TN. VALUES AROUND 70 SHOULD
BE ALONG THE GULF COAST. THIS MOISTURE COMBINED WITH RELATIVELY
STEEP MIDLEVEL LAPSE RATES SHOULD RESULT IN MODERATE INSTABILITY
FROM E TX TO CENTRAL GULF COAST STATES AND INTO PARTS OF THE TN
VALLEY. INCREASING DEEP LAYER SHEAR VECTORS BECOMING LESS PARALLEL
TO THE COLD FRONT ACROSS THIS REGION SUGGESTS SUPERCELLS WILL BE
MORE LIKELY. GIVEN THE STRENGTH OF THE LOW LEVEL SHEAR...TORNADOES
WILL BE POSSIBLE IN ADDITION TO DAMAGING WINDS AND HAIL /SOME VERY
LARGE/. SEVERE WEATHER THREAT SHOULD PERSIST ACROSS THE CENTRAL
GULF COAST STATES MONDAY NIGHT AS THE COLD FRONT SPREADS EWD INTO A
MODERATELY UNSTABLE AND STRONGLY SHEARED ENVIRONMENT.
FARTHER N INTO THE OH VALLEY INSTABILITY WILL BE WEAKER. HOWEVER...
FORCING FOR ASCENT WITH THE UPPER TROUGH AND POSSIBLY ASSOCIATED
WITH A LEAD IMPULSE WILL SUPPORT TSTM DEVELOPMENT AS THE COLD FRONT
ADVANCES EWD. BULK SHEAR VECTORS ORIENTED MORE PARALLEL TO THE
FRONT SUGGEST A LINEAR MODE WITH THE STRENGTH OF LOW LEVEL WINDS
/50-60 KT/ SUGGEST DAMAGING WINDS WILL BE THE PRIMARY THREAT.
..PETERS.. 04/03/2011
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