000
FXUS63 KLSX 211028
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
528 AM CDT TUE MAY 21 2013

.SHORT TERM...(THROUGH TONIGHT)
ISSUED AT 348 AM CDT TUE MAY 21 2013

FOCUS THRU THIS PERIOD WILL BE TSRA CHANCES.

SFC ANALYSIS AT 07Z DEPICTS THE EFFECTIVE SFC BNDY ACROSS WRN IA
INTO NWRN MO...THEN EXTENDING SWWD INTO ERN KS. BELIEVE THIS IS SOME
SORT OF PRE-FRONTAL TROF/DRY LINE AS IT APPEARS THE ACTUAL SFC FNT
IS STILL ACROSS ERN NEB INTO WRN KS. THIS TROF/DRY LINE SHUD MOVE
EWD RATHER SLOWLY TODAY.

A NUMBER OF QUESTIONS REMAIN ABOUT TODAY GIVEN THE SPREAD AMONG MDL
SOLNS. EXPECT ONGOING PRECIP TO GRADUALLY MOVE EWD OUT OF THE CWA
LATER THIS MORNING. BELIEVE ISOD TO SCT TSRA WILL DEVELOP THIS
AFTERNOON ALONG THE TROF/DRY LINE. SETUP TODAY DOES NOT APPEAR AS
FAVORABLE FOR SEVERE WEATHER TODAY COMPARED TO YESTERDAY.
HOWEVER...BELIEVE THE GFS/NAM ARE UNDERPLAYING THE EVENT TODAY AND
TONIGHT FOR THE CWA.

MDLS PROG CONVECTION OVER ARKLATEX REGION THIS AFTERNOON/EVE LIFTING
NEWD TONIGHT INTO THE CWA. THIS TSRA WILL BE DRIVEN BY A VORT MAX
CURRENTLY OVER NRN NM/SRN CO REGION. MDLS TO SOME DEGREE...EXCEPT
FOR THE NAM...DEVELOP A SFC WAVE ALONG THE SFC TROF TONIGHT. THIS
LOW SHUD TRAVEL NEWD ALONG THE SFC TROF. THE ECMWF/LOCAL WRF HAVE A
MORE NWRN SOLN AND THIS SEEMS REASONABLE AS THESE MDLS HAVE A FAIRLY
GOOD HANDLE CURRENTLY ON THE STRENGTH OF THIS SYSTEM. IF THIS SOLN
VERIFIES...THIS LOW WILL PROVIDE ENHANCED SHEAR AS WELL AS ALLOW
STEEPER LAPSE RATES TO ADVECT INTO THE AREA. GIVEN PROGD HODOGRAPHS
AND TIMING...BELIEVE TSRA WILL BE LINEAR BY THE TIME THEY ENTER THE
CWA.

IF THIS NRN SOLN IS CORRECT...THE DAY SHIFT MAY NEED TO CONSIDER A
FLASH FLOOD WATCH FOR ERN PORTIONS OF THE CWA.

AS FOR TEMPS...TRENDED AOA WARMEST MOS FOR TODAY AND COOLER FOR
TONIGHT AS THE ACTUAL CDFNT FINALLY MOVES THRU THE AREA.


TILLY

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 440 AM CDT TUE MAY 21 2013

FOCUS STARTS TO SHIFT TO TEMPS AS PRECIP FINALLY MOVES E OF THE
AREA.

WITH FOCUS ON TODAY AND TONIGHT...ONLY MINOR CHANGES WERE MADE TO
THE PREV FORECAST AS MUCH OF IT STILL APPEARS TO BE ON TRACK. MDLS
ARE IN REMARKABLY GOOD AGREEMENT THRU THE PERIOD WRT MASS FIELDS.

UNCERTAINTY REMAINS FOR TEMPS ON WED/THURS. MDLS SUGGEST TEMPS
WILL STRUGGLE TO REACH 70S. HOWEVER...GIVEN THAT IT IS MAY...IF
ANY SUN MANAGES TO MAKE IT THRU THE CLOUDS...WUD BE SURPRISED IF
TEMPS DID NOT AT LEAST BRIEFLY REACH UPPER 70S OR INTO THE LOWER
80S. WITH UPPER RIDGE BUILDING INTO THE AREA ON SAT AND
BEYOND...TEMP FORECAST BECOMES MORE QUESTIONABLE WITH DIFFERING
SOLNS AT THE SFC. FOR NOW...MADE ONLY MINOR CHANGES...BUT BELIEVE
A TREND TWD THE GFS MAY BE NEEDED WITH A WARMER AND DRIER SOLN.

TILLY

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1241 AM CDT TUE MAY 21 2013

ACTIVE/MOST INTENSE CONVECTION HAS BEEN RIDING OUTFLOW BOUNDARY
OVER THE LAST FEW HOURS...AND IS NOW IN THE PROCESS OF EXITING OUR
CWA. HAVE CONTINUED SHOWERS IN THE WAKE OF THE MOST INTENSE
CONVECTION FOR SEVERAL MORE HOURS IN STL AREA AS ELEVATED PRECIP
CONTINUES TO PERCOLATE OVER S CENTRAL MO AND MOVE NE.  ITS
CERTAINLY POSSIBLE THAT RESDIUAL INSTABILITY AND INCREASING
SOUTHERLY FLOW OVERNIGHT COULD REFIRE ELEVATED CONVECTION...BUT
FOR THE TIME BEING HAVE HELD STORMS OUT OF ALL TAFS FOR THE
REMAINDER OF THE OVERNIGHT HOURS. TAFS FOR THE REMAINDER OF THE
NIGHT WILL GENERALLY TREND TO VFR WITH CIGS AOA 8KFT...BUT WILL
CERTAINLY NEED TO WATCH FOR THE DEVELOPMENT OF SOME STRATUS
DURING THE PREDAWN HOURS. HAVE NOT MADE ANY SIGNIFICANT CHANGES
TO TUESDAYS TRENDS...WITH THE REINTRODUCTION OF TSRA BY EARLY/MID
AFTERNOON.

SPECIFICS FOR KSTL...CIGS AOA 8KFT SHOULD BE THE RULE DURING THE
PREDAWN HOURS...WITH A FEW LINGERING SHOWERS STILL POSSIBLE
THROUGH 08Z. SHOULD SEE A BIT OF CU FORM BY MID MORNING...FOLLOWED
BY A THREAT OF THUNDERSTORMS BY MID AFTERNOON.

TRUETT

&&

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

$$

WFO LSX