Possible Severe Weather on Thursday Feb 23?

[Jim Martin]

I just became aware of this for Thursday for the Significant Tornado Parameter. Please chime in.

[andyhb]

Needs more turning between H5 and H85, but the instability looks good.

[andyhb]

I've started a thread in the SE forum based on the new day 3/4.

[Srain]

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

[Ed Lizard]

The GFS is no fun at all, hanging the upper trough back and letting the front pass without assistance. The Euro is somewhat happier in that regard. Its upper low seems to phase with a Northern disturbance, while the GFS misses the boat.