SWODY1
SPC AC 171609
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1109 AM CDT FRI SEP 17 2010
VALID 171630Z - 181200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
OVER PARTS OF THE CNTRL PLAINS AND MID/LOWER MO VALLEY...
...CNTRL PLAINS/MID AND LOWER MO VALLEY...
12Z OBSERVED SOUNDINGS AND SATELLITE-DERIVED PW IMAGERY SHOW MODEST
MOISTURE CONTENT /I.E. DEW POINTS IN THE 50S TO LOW 60S AND PW
VALUES OF 1.0-1.3 INCHES/ PRESENT OVER THE REGION...WITH THE TRUE
MARITIME TROPICAL AIR MASS DISPLACED WELL TO THE S...AHEAD OF
INITIAL FRONTAL SURGE OVER ERN TX INTO THE LOWER MS VALLEY.
NONETHELESS...THE PRESENCE OF A STEEP LAPSE RATE ENVIRONMENT AND
DAYTIME HEATING WILL YIELD A MODERATELY UNSTABLE AIR MASS BY
AFTERNOON WITH MLCAPE VALUES APPROACHING 2000-2500 J/KG.
AS MENTIONED IN PREVIOUS DAY ONE DISCUSSIONS...LARGE-SCALE FORCING
FOR ASCENT WILL REMAIN NEGLIGIBLE THROUGH MUCH OF THE DIURNAL
HEATING CYCLE. HOWEVER...12Z MODEL GUIDANCE AND MORNING WATER VAPOR
IMAGERY SUGGEST THAT REGION MAY BE GLANCED BY A LOW AMPLITUDE
IMPULSE TRANSLATING ESEWD FROM THE NRN HIGH PLAINS. WHEN COUPLED
WITH A DEEPENING/STRENGTHENING CIRCULATION ATTENDANT TO
FRONTOGENETIC COLD FRONT...SETUP SHOULD ALLOW FOR THE DEVELOPMENT OF
ISOLATED TO SCATTERED TSTMS LATE THIS AFTERNOON INTO EVENING ACROSS
PARTS OF IA/NEB.
REGION WILL RESIDE ALONG THE SRN FRINGE OF STRONGER MID AND
HIGH-LEVEL CYCLONIC FLOW ATTENDANT TO UPPER LOW OVER CNTRL CANADA
WITH SUFFICIENT /30-40 KT/ DEEP WLY SHEAR TO SUPPORT ORGANIZED STORM
MODES INCLUDING SUPERCELLS. WHILE A TORNADO OR TWO WILL BE POSSIBLE
WITHIN THE FIRST HOUR OR TWO AFTER STORM INITIATION...A GENERAL
ANAFRONTAL AIR FLOW REGIME WILL LIKELY RESULT IN STORMS
TRANSITIONING TO MORE OUTFLOW DOMINANT WITH THE PRIMARY HAZARDS
BEING LARGE HAIL AND DAMAGING WINDS. THIS WIND/HAIL THREAT MAY
PERSIST INTO TONIGHT AS LOW-LEVEL INFLOW IS ENHANCED BY A
STRENGTHENING NOCTURNAL LLJ.
...CAROLINAS/SERN VA...
SHORT WAVE TROUGH CURRENTLY MOVING THROUGH THE CUMBERLAND PLATEAU
WILL PROGRESS EWD INTO THE PIEDMONT AND COASTAL PLAIN LATER TODAY.
AT THE SAME TIME...A COLD FRONT WILL CONTINUE TO PUSH SEWD THROUGH
THE REGION...PROVIDING THE FOCUS FOR DIURNAL STORM DEVELOPMENT. AIR
MASS AHEAD OF THE FRONT IS RATHER MOIST WITH DEW POINTS IN THE 60S.
AND WHILE MIDLEVEL LAPSE RATES ARE NOT PARTICULARLY STEEP...THE
PRESENCE OF STRONG DIABATIC HEATING SHOULD SUPPORT MLCAPE INCREASING
TO 1000-1500 J/KG THIS AFTERNOON...ALONG WITH STEEPENING LOW-LEVEL
LAPSE RATES. AS SUCH...SOME RISK FOR ISOLATED STRONG WIND GUSTS
WILL EXIST WITH ANY STRONGER STORMS THAT MAY DEVELOP.
..MEAD/BROYLES.. 09/17/2010
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