Wednesday, April 11, 2012

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 110732
SWODY3
SPC AC 110730

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT WED APR 11 2012

VALID 131200Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CENTRAL AND
SRN PLAINS...

...SYNOPSIS...
UPPER FLOW PATTERN WILL REMAIN AMPLIFIED THIS FORECAST PERIOD
REINFORCING AND STRENGTHENING A SWLY FLOW REGIME ACROSS THE
CENTRAL/SRN PLAINS TO THE GREAT LAKES/OH VALLEY REGION. A LARGE
PACIFIC TROUGH WILL CONTINUE TO DIG SEWD...DEEPENING THE WRN STATES
LONGWAVE TROUGH...WHILE DOWNSTREAM HEIGHTS RISE E OF THE MS RIVER AS
A RIDGE SHIFTS INTO THE ERN CONUS.

AT THE SURFACE...AN AREA OF LOW PRESSURE WILL TRACK FROM NEB INTO
NWRN MN ON FRI ATTENDANT TO THE PROGRESSIVE D2 MIDLEVEL TROUGH
EXPECTED TO BE OVER THE CENTRAL PLAINS AT 12Z FRI. MEANWHILE...LEE
TROUGHING WILL BE MAINTAINED OVER THE CENTRAL/SRN HIGH PLAINS
BENEATH SWLY FLOW ALOFT...WITH A SECOND SURFACE LOW DEVELOPING IN
ERN CO FRI AFTERNOON.

...OK/KS...
A DRY LINE IS EXPECTED TO EXTEND SWD FROM THE NEB SURFACE LOW
THROUGH CENTRAL KS...WRN OK...THEN SWWD INTO SW TX AT 12Z FRI.
GFS/ECMWF SUGGEST THIS BOUNDARY SHIFTS A LITTLE EWD FRI MORNING...
BUT BACKING/STRENGTHENING LOW LEVEL WINDS IN RESPONSE TO SURFACE
PRESSURE FALLS WITH THE LEE TROUGH ARE EXPECTED TO SUPPORT MOISTURE
RETREATING WNWWD. SURFACE DEWPOINTS IN THE LOWER 60S SHOULD EXTEND
INTO WRN/NWRN OK BY LATE FRI AFTERNOON AND THEN INTO CENTRAL KS FRI
EVENING AS THE SLY LLJ UNDERGOES FURTHER STRENGTHENING.

MOST MODELS INDICATED CONVECTION/TSTM DEVELOPMENT COULD OCCUR PRIOR
TO PEAK HEATING /BY 18Z/ ACROSS THE WARM SECTOR FROM N TX THROUGH OK
TO ERN KS. INCREASING INSTABILITY AND SUFFICIENT DEEP LAYER SHEAR
WOULD SUPPORT ORGANIZED STRONG TO SEVERE STORMS WITH THIS ACTIVITY.
ADDITIONAL TSTM DEVELOPMENT IS THEN EXPECTED WNWWD LATER FRI
AFTERNOON AS THE BOUNDARY LAYER MOISTENS ALONG AND E OF THE
RETREATING DRY LINE. STRONG SURFACE HEATING INVOF THIS BOUNDARY AND
BENEATH STEEP MIDLEVEL LAPSE RATES SHOULD ALLOW FOR STRONGER
INSTABILITY. STRENGTHENING SWLY MIDLEVEL AND SLY LOW LEVEL WINDS
ACROSS WILL RESULT IN EFFECTIVE BULK SHEAR UP TO 50 KT ORIENTED
PERPENDICULAR TO THE DRY LINE LINE...SUPPORTING THE POTENTIAL FOR
TORNADIC SUPERCELLS WITH ADDITIONAL THREATS FOR VERY LARGE HAIL AND
DAMAGING WINDS. GIVEN THE STRENGTHENING WIND FIELDS INTO THE
EVENING...SEVERE WEATHER THREATS ARE EXPECTED TO PERSIST AFTER DARK
INCLUDING A THREAT FOR TORNADOES.

THE EARLY WAVE AND IMPACT OF THE MORNING/EARLY AFTERNOON STORMS
COULD AFFECT OVERALL DESTABILIZATION...AND THUS LOWER PROBABILITIES
WILL BE MAINTAINED...BUT HIGHER PROBABILITIES MAY BE NEEDED IN LATER
OUTLOOKS.

..PETERS.. 04/11/2012

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