DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CST TUE FEB 21 2012

VALID 231200Z - 241200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM SRN AND ERN TX INTO A
PORTION OF THE SERN STATES...

...SYNOPSIS...

MODELS HAVE CONVERGED TO SIMILAR SOLUTIONS WITH REGARD TO EVOLUTION
OF SYNOPTIC PATTERN. BROAD UPPER TROUGH WILL REMAIN DOMINANT...AND
THIS FEATURE IS FORECAST TO AMPLIFY OVER THE MS VALLEY AS A STRONG
UPPER JET DROPS SEWD THROUGH THE INTERMOUNTAIN WEST...REACHING THE
SRN PLAINS TOWARD THE END OF THE PERIOD. MEANWHILE...SWLY LLJ WILL
STRENGTHEN OVER THE SERN STATES AND OH VALLEY IN ASSOCIATION WITH
THE AMPLIFYING NRN STREAM TROUGH. ECMWF HAS TRENDED TOWARD A SLOWER
EJECTION OF SRN STREAM UPPER LOW THAT WILL CUTOFF OVER NRN MEXICO
AND IS NOW SIMILAR TO THE GFS WITH THE NAM STILL BEING THE SLOWEST
MODEL. THE UPPER LOW WILL LIKELY REACH SRN TX LATER THURSDAY NIGHT.
AT THE SURFACE PRIMARY CYCLONE IS FORECAST TO CONSOLIDATE OVER THE
OH VALLEY OR GREAT LAKES WHILE A TRAILING COLD FRONT ADVANCES SEWD
THROUGH THE SRN PLAINS...LOWER MS VALLEY AND INTO WRN PORTIONS OF
THE SERN STATES.

...SERN STATES...

POTENTIAL FOR SIGNIFICANT SEVERE WEATHER WILL EXIST THURSDAY EVENING
AND OVERNIGHT.

STRENGTHENING SWLY BOUNDARY LAYER WINDS WILL CONTRIBUTE TO NEWD
TRANSPORT OF MODIFYING GULF AIR WITH DEWPOINTS FROM THE UPPER 60S
OVER SRN AND ERN TX INTO THE GULF COASTAL STATES TO NEAR 50 OVER SRN
PORTIONS OF THE OH VALLEY. GREATEST INSTABILITY WILL LIKELY DEVELOP
OVER THE LOWER MS VALLEY REGION JUST AHEAD OF THE FRONT WHERE PLUME
OF STEEPER LAPSE RATES WILL ADVECT EWD AND OVERTAKE THE WRN EDGE OF
THE MOIST AXIS. MLCAPE IN THIS REGION COULD RANGE FROM 1000-1500
J/KG. HOWEVER...THE RETURNING LOW LEVEL MOISTURE MIGHT CONTRIBUTE TO
THE DEVELOPMENT OF CLOUDS OVER A PORTION OF THIS REGION...AND THE
ATMOSPHERE WILL LIKELY REMAIN CAPPED TO SURFACE BASED CONVECTION
MUCH OF THE DAY. MODEL CONSENSUS IS THAT STORMS WILL DEVELOP BY
EARLY EVENING IN ZONE OF HEIGHT FALLS AND INCREASING FRONTAL
CONVERGENCE ASSOCIATED WITH THE AMPLIFYING WAVE AND STRENGTHENING
LLJ. ACTIVITY WILL EXIST WITHIN A STRONG KINEMATIC ENVIRONMENT AS
LLJ INCREASES TO IN EXCESS OF 50 KT WITH STRONG DEEP LAYER WINDS AND
VERTICAL SHEAR. THIS ENVIRONMENT WILL SUPPORT ORGANIZED STORMS
INCLUDING SUPERCELLS AND BOWING STRUCTURES WITH UPSCALE GROWTH
LIKELY OVERNIGHT. LARGE HAIL...DAMAGING WIND AND A FEW TORNADOES
WILL BE POSSIBLE AS STORMS DEVELOP EWD.


...OH VALLEY...

MOISTURE AND INSTABILITY WILL BE MORE LIMITED WITH NWD EXTENT INTO
THE OH VALLEY WITH MUCAPE AOB 500 J/KG LIKELY. FORCING WITHIN
FRONTAL ZONE WILL PROMOTE A LOW TOPPED LINE OF CONVECTION EMBEDDED
WITHIN STRONG VERTICAL SHEAR DURING THE AFTERNOON AND EVENING.
DESPITE THE LIMITED INSTABILITY SOME THREAT WILL EXIST FOR ISOLATED
DAMAGING WIND. LOW SEVERE PROBABILITIES HAVE BEEN INTRODUCED...BUT
AREA MAY NEED TO BE INCLUDED IN A SLIGHT RISK IN LATER OUTLOOKS.

...TX...

A FEW STORMS WILL PROBABLY DEVELOP ALONG SWRN EXTENSION OF THE FRONT
INTO ERN AND SRN TX WHERE STEEP LAPSE RATES AND A MOIST BOUNDARY
LAYER WILL PROMOTE MODERATE INSTABILITY. HOWEVER...THE ATMOSPHERE IN
THIS REGION WILL BE MORE CAPPED AND COVERAGE OF STORMS...ESPECIALLY
ACROSS SRN TX WILL BE MODULATED BY TIMING OF SRN STREAM WAVE. ANY
STORMS THAT DEVELOP WILL BE CAPABLE OF MAINLY ISOLATED DAMAGING WIND
AND HAIL.

..DIAL.. 02/21/2012