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000
FXUS63 KLSX 192339
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
639 PM CDT SUN MAY 19 2013

.SHORT TERM...(THROUGH LATE TONIGHT)
ISSUED AT 331 PM CDT SUN MAY 19 2013

FOCUS FOR STORMS EARLY THIS EVENING IS BACK OVER EASTERN KS/WESTERN
MO...THEN HAVE THIS COMPLEX OF STORMS MOVE EAST INTO
CENTRAL/NORTHEAST MO BY 03Z. STILL SOME UNCERTAINTY ON EXACT
PLACEMENT AND STRENGTH OF STORMS AS THEY MOVE EAST INTO FORECAST
AREA. 12Z MODELS ALL OVER THE PLACE WITH SOME FOCUSING MAIN AREA OF
STORMS ALONG AND SOUTH OF I-70...WHILE OTHERS HAVE A LONG LINE OF
STORMS MOVE ACROSS ENTIRE FORECAST AREA. FOR NOW HAVE AREA OF STORMS
MOVE ACROSS REGION...GRADUALLY WEAKENING/DIMINISHING TOWARDS
DAYBREAK...GOING FROM LIKELY POPS DOWN TO JUST CHANCE POPS BY 11Z.
BEST CHANCES WILL BE OVER WESTERN HALF OF FORECAST AREA. AS FOR
SEVERE WEATHER CHANCES...DECENT CAPES/PWS...LOW LEVEL JET...AND
SHORTWAVE SLIDING THROUGH AREA TONIGHT. SO WESTERN PORTIONS OF
FORECAST AREA STILL IN A SLIGHT RISK OVERNIGHT...WITH MAIN THREAT
BEING DAMAGING WINDS.

OTHERWISE...GUSTY SOUTHEAST TO SOUTH WINDS TO DIMINISH AFTER SUNSET.
MILD WEATHER TO PERSIST WITH LOWS ONLY IN THE MID TO UPPER
60S...WITH LOW 70S IN STL METRO AREA.

BYRD

.LONG TERM...(MONDAY THROUGH NEXT SUNDAY)
ISSUED AT 331 PM CDT SUN MAY 19 2013

CURRENT INDICATIONS BASED ON THE DETERMINISTIC MODELS AND CONVECTION
ALLOWING MODELS IS THAT ANY THUNDERSTORMS REMAINING FROM THE OVERNIGHT
MCS SHOULD BE IN A DRASTICALLY WEAKENED STATE AT DAYBREAK. GIVEN THAT THE
PRIMARY SHORT WAVE TROF WILL HAVE ALREADY ROTATED NEWD INTO IOWA
AND A VEERED WSWLY LLJ...ANY REMAINING SHOWERS AND THUNDERSTORMS
WILL MOST LIKELY BE LOCATED FROM SOUTHWEST/SOUTH CENTRAL IL ACROSS
SE MO. THESE SHOULD DIMINISH BY MID MORNING AS LARGE SCALE SUBSIDENCE
OVERSPREADS THE REGION. IN THE WAKE OF THIS ACTIVITY AND GIVEN THE
TENDENCY TOWARDS CUMULIFORM CLOUDS...GOOD HEATING WILL COMMENCE.
THIS HEATING COMBINED WITH A MOIST BOUNDARY LAYER AND STEEP MID
LEVEL LAPSE RATES WILL CONTRIBUTE TO MODERATE-STRONG INSTABILITY
AND WEAK CONVECTIVE INHIBITION ACROSS THE ENTIRE AREA BY MID
AFTERNOON. SOUTHWESTERLY DEEP LAYER SHEAR AOA 40 KTS WOULD FAVOR
DISCRETE TO SEMI-DISCRETE SUPERCELLS AS THE DOMINATE STORM MODE
INITIALLY. AT THIS WE ARE EXPECTING A FAVORED WSW-ENE CORRIDOR
FOR STORM DEVELOPMENT AFTER 21Z FROM AROUND JEFFERSON CITY TO
BOWLING GREEN...ALTHO THIS AXIS COULD BE A BIT FURTHER SOUTH
DEPENDING ON ANY RESIDUAL BOUNDARIES. MERGERS AND ADDITIONAL
DEVELOPMENT WITHIN THIS ZONE AND UPSTREAM SHOULD RESULT IN A MIX
OF STORM MODES BY LATE AFTERNOON AND EVENING WITH POTENTIAL FOR
SUPERCELLS AND BOWING LINEAR SEGMENTS. THE OVERALL COVERAGE OF
STORMS SHOULD INCREASE DURING THE EVENING AS THE NEXT UPSTREAM
SHORT WAVE SPREADS LARGE SCALE ASCENT INTO THE REGION...ALSO
CONTRIBUTING TO UPSCALE STORM GROWTH. THERE EVENTUALLY COULD BE A
HEAVY RAIN THREAT FROM CENTRAL THROUGH EAST CENTRAL MO DUE TO
PERSISTENT AND TRAINING CONVECTION...BUT THE EXACT LOCATION IS TOO
DIFFICULT TO PINPOINT AT THIS POINT.

THE CONVECTIVE DETAILS BECOME LESS DEFINED ON TUESDAY DUE TO THE
POTENTIAL FOR RESIDUAL SHOWERS/STORMS FROM MONDAY NIGHT AND THE
PRESENCE OF MESOSCALE BOUNDARIES. THE OVERALL SYNOPTIC PATTERN
FEATURING THE UPPER TROF PROGRESSING EASTWARD WITH THE ATTENDANT
COLD FRONT MOVING THRU THE CWA DURING THE LATE AFTERNOON/EVENING
WOULD FAVOR HIGH THUNDERSTORM CHANCES...ESPECIALLY THE SE HALF OF
THE CWA. DEEP LAYER SHEAR OF 30-40 KTS AND WEAK-MODERATE INSTABILITY
WOULD CONTINUE TO FAVOR ORGANIZED-MIXED MODE SEVERE STORMS.

THE BOUNDARY FINALLY LOOKS TO PASS SOUTH OF THE AREA BY LATE
WEDNESDAY WITH ANOTHER REINFORCING BOUNDARY ON THURSDAY. THE PATTERN
THEN IS DOMINATED BY WEAK NW FLOW ON THE BACKSIDE OF THE UPPER TROF
AND LOOKS DRY THURSDAY NIGHT-SAT MORNING. THEREAFTER RETURN FLOW AND
WEAK DISTURBANCES PASSING THRU THE PLAINS UPPER RIDGE AND INTO THE
MID/UPPER MS VALLEY WILL BRING A RE-NEWED CHANCE OF
THUNDERSTORMS....ESPECIALLY THE NRN HALF OF THE CWA.

GLASS

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 622 PM CDT SUN MAY 19 2013

A COUPLE OF LINES OF THUNDERSTORMS HAVE DEVELOPED ACROSS EASTERN
KS AND WRN MO EARLY THIS EVENING. THESE THUNDERSTORM COMPLEXES
WILL MOVE EWD OVER THE NEXT SEVERAL HOURS AND EVENTUALLY REACH
KCOU AND KUIN. IT IS UNCLEAR WHETHER THE STORMS WILL HOLD TOGETHER
LONG ENOUGH TO REACH THE KSTL METRO AREA. ANOTHER ROUND OF STORMS
IS EXPECTED TOMORROW AFTN/EVENING AS AN UPPER LEVEL DISTURBANCE
APPROACHES THE AREA AHEAD OF A SLOW-MOVING COLD FRONT. PREVAILING
WINDS OUTSIDE OF THUNDERSTORMS WILL GENERALLY RETAIN A SLY
COMPONENT...VARYING FM SELY TO SWLY WITH GUSTS TO 20-25 KTS AT
TIMES. BRIEF PDS OF IFR CONDITIONS ARE EXPECTED IN THUNDERSTORMS.

SPECIFICS FOR KSTL...A COUPLE OF THUNDERSTORM COMPLEXES HAVE
DEVELOPED AND ARE EXPECTED TO MOVE EWD TONIGHT HOWEVER IT IS
UNCLEAR ATTM WHETHER THE STORMS WILL HOLD TOGETHER LONG ENOUGH TO
REACH KSTL. ANOTHER ROUND OF THUNDERSTORMS IS EXPECTED TOMORROW
AFTN/EVENING AHEAD OF A SLOW-MOVING CDFNT. PREVAILING WINDS
OUTSIDE OF THUNDERSTORMS WILL GENERALLY RETAIN A SLY
COMPONENT...VARYING FM SELY TO SWLY WITH GUSTS TO 20-25 KTS AT
TIMES.

KANOFSKY

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
IL...NONE.
&&

$$

WFO LSX