000
FXUS63 KLSX 200937
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
437 AM CDT MON MAY 20 2013

.SHORT TERM...(THROUGH TONIGHT)
ISSUED AT 358 AM CDT MON MAY 20 2013

MORNING CONVECTION WILL CONTINUE TO MOVE EWD THRU THE CWA EARLY
THIS MORNING. CURRENTLY DO NOT ANTICIPATE OUTFLOW FROM THIS
CONVECTION IMPACTING THE CWA LATER TODAY AS IT SHUD CONTINUE WELL
OUTSIDE OF THE CWA.

THE CDFNT CURRENTLY OVER ERN KS WILL MOVE EWD TODAY AND SHUD BE
JUST W OF THE CWA AROUND NOON. WITH THE ENTIRE AREA IN THE WARM
SECTOR...EXPECT AREA TO RECOVER WELL WITH AMPLE INSOLATION.
MDL SOLNS DIFFER REGARDING EXACTLY HOW TSRA WILL UNFOLD TODAY.
CONVECTION ALLOWING MDLS SUGGEST FOCUS WILL BE SW OF THE CWA THIS
AFTERNOON/EVE WITH THIS LINE MOVING NEWD INTO THE AREA LATE
TONIGHT. THE OPR MDLS SUGGEST TSRA WILL DEVELOP JUST AHEAD OF THE
CWA LATE THIS MORNING OR EARLY AFTERNOON. INTERESTINGLY...THE
LOCAL 4KM WRF PROVIDES A MERGER OF THESE TWO SOLNS...WHICH SEEMS
THE MOST LIKELY. WHILE TIMING REMAINS A QUESTION...WHAT DOES FORM
SHUD EVOLVE UPSCALE INTO A LINEAR MODE AS IT MOVES ACROSS THE
AREA. TSRA SHUD BE ON THE ERN EDGE OF THE CWA BY SUNRISE TUES.

LITTLE CHANGE WAS MADE TO TEMPS...KEEPING THE FORECAST AOA THE
WARMEST MOS.

TILLY

.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 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 105 AM CDT MON MAY 20 2013

LINE OF TSRA WILL TAKE MUCH OF THE NIGHT TO WORK ITS WAY THRU THE
FA AND SHOULD AFFECT ALL TAF SITES BEFORE SUNRISE. UNCLEAR WHETHER
THERE WILL BE A BREAK BETWEEN THIS AND WHAT DEVELOPS UPSTREAM FROM
IT LATER ON MONDAY...BUT FOR NOW...HAVE FORECASTED THE TAFS AS IF
THERE WILL BE. THE SECOND...STRONGER ROUND...SHOULD GET GOING BY
EARLY AFTERNOON AND SLOWLY EXPAND SEWD. NOT ENTIRELY CERTAIN WHERE
THIS WILL HIT WITHOUT A CLEAR FEATURE TO FOLLOW AND THUS HAVE
GONE VCTS FOR NOW BUT WILL LIKELY HAVE TO RAMP UP THE FORECAST AT
SOME OF THE TERMINALS. S SFC WNDS WILL CONTINUE THRU THE PERIOD
BECOMING GUSTY ESPECIALLY DURING THE DAY ON MONDAY.

SPECIFICS FOR KSTL...VFR CONDITIONS EXPECTED OUTSIDE OF TSRA...ONE
ROUND OF TSRA FOR LATE TONIGHT...ANOTHER ROUND OF TSRA FOR LATER
ON MONDAY. RIGHT NOW IT APPEARS THE SECOND ROUND OF TSRA WILL NOT
WORK INTO THE TERMINAL AREA UNTIL EARLY EVENING AFTER AFFECTING
AREAS JUST TO THE NW AND THEN STAY FOR A WHILE.

TES

&&

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

$$

WFO LSX