000
FXUS63 KLSX 150501
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1201 AM CDT SAT JUN 15 2013

.UPDATE...
ISSUED AT 947 PM CDT FRI JUN 14 2013

MCS LOCATED FROM ERN NEBRASKA INTO WESTERN IOWA IS LOCATED WITHIN
A RESERVOIR OF VERY BUOYANT AIR AND NEAR THE NOSE OF A 40+ KT
SSWLY LLJ. PRESENT INDICATIONS ARE THAT THIS SYSTEM SHOULD BEGIN
TO TAKE A SEWD TURN WITHING THE NEXT 3 HOURS AS THE LLJ VEERS TO
MORE WESTERLY DURING THE LATE EVENING AND OVERNIGHT HOURS...MOVING
ALONG THE PERIPHERY OF INSTABILITY GRADIENT. THIS SHOULD BRINGING
A WEAKENING MCS INTO THE NORTHERN THIRD OF THE CWA OVERNIGHT INTO
EARLY SATURDAY MORNING. ALREADY MADE SOME ADJUSTMENTS TO THE POPS
AND WILL REFINE THEM A BIT MORE WITH THIS IN MIND.

GLASS
&&

.SHORT TERM...(THROUGH TONIGHT)
ISSUED AT 200 PM CDT FRI JUN 14 2013

FOCUS FOR TONIGHT CONTINUES TO BE POPS.

ONGOING CONVECTION OVER NRN PORTIONS OF THE CWA WILL DETERMINE
EARLY EVENING POPS...BUT WITH CONVECTION DISSIPATING...MAY BE ABLE
TO CUT BACK TO CHANCE POPS. BELIEVE ONGOING CONVECTION OVER WRN IA
WILL BE THE MAIN FOCUS OF TSRA OVERNIGHT. MDLS SUGGEST THESE TSRA
WILL CONTINUE TO MOVE EWD AND GRADUALLY DEVELOP SWD AS THE LLJ
VEERS. MDLS HINT THAT TSRA MAY DEVELOP AS FAR S AS THE NRN FRINGES
OF THE STL METRO AREA.

WITH CONVECTIVE DEBRIS EXPECTED OVER MUCH OF THE AREA...HAVE
TRENDED TWD THE WARMER GUIDANCE FOR TEMPS.

TILLY

.LONG TERM...(SATURDAY THROUGH NEXT FRIDAY)
ISSUED AT 250 PM CDT FRI JUN 14 2013

(SATURDAY THROUGH MONDAY)

MAIN FOCUS WILL BE TSRA CHANCES...MAINLY SAT INTO SAT NIGHT.

TSRA SHUD BE ONGOING SAT MORNING AS MENTIONED ABOVE. THESE TSRA
SHUD MOVE EWD AND DISSIPATE DURING THE MORNING HOURS. TSRA SHUD
REDEVELOP ALONG/JUST AHEAD OF AN APPROACHING CDFNT DURING THE LATE
AFTERNOON INTO THE EARLY EVENING HOURS. SOME QUESTION REMAINS
REGARDING WHAT MODE THE CONVECTION WILL BE AND WILL BE LARGELY
DETERMINED BY EXACTLY WHERE AND WHEN TSRA DEVELOP. BELIEVE STORMS
WILL START AS SUPERCELLS...IF ENUF SPACING IS REALIZED AND STORMS
REMAIN DISCRETE. TSRA SHUD EVENTUALLY DEVELOP UPSCALE INTO A LINE
WITH TSRA GRADUALLY SINKING SWD WITH THE CDFNT. TSRA THAT DEVELOP
MAY BE SEVERE WITH DAMAGING WINDS AS THE PRIMARY THREAT DURING THE
LINEAR STAGE AND LARGE HAIL DURING THE SUPERCELL STAGE. A THREAT
FOR TORNADOES CAN NOT BE RULED OUT DURING EITHER OF THESE
STAGES...BUT MDLS HAVE DIFFERING SOLNS REGARDING HOW MUCH LOW
LEVEL SHEAR WILL BE AVAILABLE. AS THE EVENT CONTINUES INTO SAT
NIGHT...THREAT SHUD SWITCH TO HEAVY RAIN AS THE FNT BECOMES
STATIONARY OR NEARLY AND 850H FLOW RUNS WITH THE FNT. AS IT HAS
BEEN A WHILE SINCE THE LAST RA...WILL HOLD OFF ON A WATCH FOR NOW
BUT ONE MAY BE NEEDED LATER.

TSRA SHUD CONTINUE INTO SUN ALONG THE FNT. MDLS DIFFER ON PLACEMENT
OF THE FNT WITH THE GFS/ECMWF PUSHING THE FNT S OF THE CWA DURING
THE DAY AND THE NAM/LOCAL WRF KEEPING IT OVER THE MID PORTIONS OF
THE CWA AND NOT MOVING S OF THE CWA UNTIL MON. FOR NOW...HAVE
TRENDED TWD THE GFS/ECMWF SOLNS...BUT HAVE KEPT POPS SOMEWHAT HIGH
TO MAINTAIN CONTINUITY WITH THE PREV FCST AND TO ACCOUNT FOR THE
NAM/LOCAL WRF SOLNS.

HAVE TRENDED TWD THE COOLER GUIDANCE FOR TEMPS WITH AMPLE CLOUD
COVER AND PRECIP EXPECTED THRU MUCH OF THE PERIOD.

(TUESDAY THROUGH FRIDAY)

CONTINUED COOL TREND WITH REGION UNDER NW FLOW AND LARGE SFC RIDGE
IN PLACE.

TILLY

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1159 PM CDT FRI JUN 14 2013

MCS OVER SOUTHERN IOWA BEGINNING TO MAKE A MORE SOUTHEASTWARD
MOTION...SO WILL BEGIN TO MOVE INTO NORTHERN PORTIONS OF FORECAST
AREA AFTER 09Z. SO ADJUSTED TIMING OF TEMPO GROUP AT KUIN...TO
BETWEEN 09Z AND 13Z. WITH A MORE SOUTHEASTWARD TRACK...COULD
AFFECT KCOU...SO ADDED VCTS MENTION THERE AFTER 10Z. AS FOR METRO
AREA...STILL UNSURE ABOUT HOW FAR SOUTH IT WILL GET...FOR NOW HAVE
ADDED VCNTY SHOWER MENTION BEGINNING AROUND 13Z. OTHERWISE...
SHOULD SEE A BIT OF A BREAK IN ACTIVITY FROM MID MORNING THROUGH
EARLY AFTERNOON...THEN SCATTERED ACTIVITY IS POSSIBLE WITH BETTER
CHANCES IN THE EVENING AS MAIN COLD FRONT BEGINS TO MOVE INTO THE
FORECAST AREA. TIMING AND COVERAGE STILL HARD TO PIN DOWN...SO
JUST HAVE VCTS MENTION. OTHERWISE...SOUTHEAST WINDS TO BECOME
SOUTHERLY BY DAYBREAK...WITH A TURN TO THE SOUTHWEST BY THIS
EVENING.

SPECIFICS FOR KSTL...MCS OVER SOUTHERN IOWA BEGINNING TO MAKE A
MORE SOUTHEASTWARD MOTION...SO WILL BEGIN TO MOVE INTO NORTHERN
PORTIONS OF FORECAST AREA AFTER 09Z. WITH A MORE SOUTHEASTWARD
TRACK...STILL UNSURE ABOUT HOW FAR SOUTH IT WILL GET. FOR NOW HAVE
ADDED VCNTY SHOWER MENTION BEGINNING AROUND 13Z. OTHERWISE...
SHOULD SEE A BIT OF A BREAK IN ACTIVITY FROM 17Z THROUGH 20Z...THEN
SCATTERED ACTIVITY IS POSSIBLE WITH BETTER CHANCES IN THE EVENING
AS MAIN COLD FRONT BEGINS TO MOVE INTO THE FORECAST AREA. TIMING
AND COVERAGE STILL HARD TO PIN DOWN...SO JUST HAVE VCTS MENTION
AFTER 06Z SUNDAY. OTHERWISE...SOUTH WINDS TO PERSIST THEN VEER TO
THE SOUTHWEST BY 06Z SUNDAY.

BYRD
&&

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

$$
WFO LSX