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000
FXUS63 KLSX 251256
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
756 AM CDT SAT MAY 25 2013

.UPDATE...
ISSUED AT 755 AM CDT SAT MAY 25 2013

UPDATED GRIDS/ZONES FOR ACTIVITY THAT HAS FIRED UP SOUTH OF MAIN
MCS...EXTENDING FROM NEAR IRK TO SZL TO SGF. SO RAISED POPS ACROSS
PORTIONS OF FORECAST AREA THIS MORNING AS THIS LINE MOVES EAST.

BYRD
&&

.SHORT TERM...(THROUGH LATE THIS AFTERNOON)
ISSUED AT 316 AM CDT SAT MAY 25 2013

COMPLEX FORECAST FOR TODAY. A BROAD LOW LEVEL WAA ZONE SPANNING FROM
NORTH CENTRAL IL WESTWARD INTO NEBRASKA IS RESPONSIBLE FOR AN
INCREASING AMOUNT OF SHOWERS AND THUNDERSTORMS THIS MORNING...INCLUDING
ACROSS NORTHERN MO. THE MOST CONCENTRATED ZONE IS FROM WESTERN
IOWA INTO NEBRASKA WHERE AN ELONGATED MCS IS OCCURRING AT THE NOSE
OF THE 40-50 KT SWLY LLJ...WHERE ELEVATED INSTABILITY IS PRESENT
WITH MUCAPE ABOVE 1000 J/KG AND JUST AHEAD OF A WEAK SHORT WAVE
MOVING THROUGH THE UPPER RIDGE CREST. THERE IS GENERAL AGREEMENT
THAT THE SHORT WAVE WILL TRACK EASTWARD TODAY WITH A POSITION IN
NORTHERN IL BY 00Z AND IN ASSOCIATION THE LLJ WILL VEER PROVIDING
CONTINUED WAA AND TRANSPORTING MOISTURE BACK INTO THE REGION.
THESE ELEMENTS ALONE FAVOR A FORWARD PROPAGATING MCS AND CORFIDI
VECTORS AND THICKNESS FIELDS WOULD SUGGEST A ESEWD MCS MOTION.
SEVERAL CONVECTION ALLOWING RUNS OF THE NCAR 3KM WRF SUGGEST THE
MCS WILL IN FACT TRACK ESEWD WITH THE SRN PERIPHERY...WHICH WILL
ALSO CONSIST OF NEW DEVELOPMENT...MOVING THRU OR JUST NORTH OF ST
LOUIS. I HAVE TRENDED THE NEW FORECAST IN THIS DIRECTION WITH THE
POPS RAMPING UP THIS MORNING...WITH ISOLATED TO SCATTERED
ACTIVITY DUE TO WAA THRU 15Z OR SO AND THEN THE MCS WILL IMPACT
THE AREA FROM LATE MORNING INTO MID AFTERNOON...SPECIALLY NE MO
INTO WEST CENTRAL IL.

GLASS

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 316 AM CDT SAT MAY 25 2013

THE REMAINDER OF THE FORECAST IS TOUGH TRYING TO GIVE SPECIFICS.
THE AFOREMENTIONED UPPER RIDGE AXIS WILL BASICALLY BE LOCATED
THROUGH THE MID/UPPER MS VALLEY WHILE A SERIES OF WEAK SHORT WAVES
CONTINUE TO MOVE THROUGH IT TONIGHT THROUGH MONDAY. THE MODELS HAVE
WIDELY VARYING SOLUTIONS ON THE TIMING AND LOCATION OF THESE
FEATURES LEADING TO GREATER THAN NORMAL UNCERTAINTY. THE LOWER
TROP WILL CONTINUE TO FEATURE A PROMINENT WAA REGIME AND MOISTURE
AND INSTABILITY WILL CONTINUE TO IMPROVE WITH TIME. OVERALL THE
PATTERN IS SUPPORTIVE OF BOUTS OF ORGANIZED CONVECTION ASSOCIATED
WITH THE SHORT WAVES AND LLJ. THE MOST FAVORED ZONE APPEARS TO BE
THE NORTHERN THIRD THE CWA WITH LESSER CHANCES WITH SOUTHWARD
EXTENT. BY LATE MEMORIAL DAY AND INTO TUESDAY THE WARM FRONT WILL
LIFT NORTHWARD AND THE UPPER RIDGE AXIS WILL SHIFT EAST AND BUILD
THROUGH THE ERN US RESULTING IN A DIMINISHED THREAT OF SHOWERS AND
THUNDERSTORMS AND TEMPERATURES WELL INTO THE 80S. THESE ABOVE
NORMAL READINGS SHOULD PERSIST INTO THE LATER PART OF NEXT WEEK.

GLASS
&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 755 AM CDT SAT MAY 25 2013

BEST CHANCES OF STORMS WILL BE OVER NORTHERN PORTIONS OF FORECAST
AREA...THOUGH NORTH/SOUTH LINE OF STORMS HAS DEVELOPED OVER
WESTERN MO AND IS MAKING ITS WAY TOWARDS KCOU. SO HAVE TEMPO
GROUPS OF MVFR VSBYS WITH THESE STORMS FOR A FEW HOURS...BEFORE
TAPERING OFF. AS FOR METRO AREA...NOT SURE IF ANY OF IT WILL HOLD
TOGETHER BEFORE GETTING HERE...SO JUST KEPT VCSH MENTION FOR NOW.
OTHERWISE...WILL SEE A BREAK IN ACTIVITY FOR THIS AFTERNOON AND
EARLY TONIGHT BEFORE NEXT COMPLEX DEVELOPS. STILL HARD TO PIN DOWN
EXACT TIMING AND COVERAGE OF THIS...SO JUST KEPT VCTS MENTION AT
THIS TIME.

SPECIFICS FOR KSTL...BEST CHANCES OF STORMS WILL BE OVER NORTHERN
PORTIONS OF FORECAST AREA...THOUGH NORTH/SOUTH LINE OF STORMS HAS
DEVELOPED OVER WESTERN MO AND IS MAKING ITS WAY EAST THIS MORNING.
NOT SURE IF ANY OF IT WILL HOLD TOGETHER BEFORE GETTING TO THE STL
METRO AREA...SO JUST KEPT VCSH MENTION FOR NOW. OTHERWISE...WILL
SEE A BREAK IN ACTIVITY FOR THIS AFTERNOON AND EARLY TONIGHT
BEFORE NEXT COMPLEX DEVELOPS. STILL HARD TO PIN DOWN EXACT TIMING
AND COVERAGE OF THIS...SO JUST KEPT VCTS MENTION AT THIS TIME
BEGINNING AROUND 08Z SUNDAY.

BYRD
&&

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

$$
WFO LSX