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000
FXUS63 KLSX 132021
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
321 PM CDT MON MAY 13 2013

.SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)
ISSUED AT 315 PM CDT MON MAY 13 2013

THE SOUTHEASTWARD SHIFT OF THE LOW LEVEL ANTICYCLONE HAS ALLOWED THE
WARMING TREND TO GET UNDERWAY TODAY WITH TEMPS APPROACHING SEASONABLE
NORMALS. TEMPERATURES ARE WELL INTO THE 80S AND LOWER 90S ACROSS
THE CENTRAL/WESTERN PLAINS AND THAT AIR IS HEADED OUR WAY OVER THE
NEXT 24 HOURS. LOW LEVEL WAA WILL CONTINUE TONIGHT WITH SOUTHERLY
SURFACE WINDS PERSISTING. THIS WILL KEEP MINS MUCH GREATER THAN
THE PREVIOUS 2 NIGHTS/MORNINGS WHEN WE FLIRTED WITH RECORD MINS
AND HAD SOME FROST. SAY GOODBYE TO THAT...AND NOW WE MAY BE
APPROCHING RECORD HIGHS ON TUESDAY WITH TEMPERATURES MORE TYPICAL
OF LATE JUNE/EARLY JULY NORMALS. HEIGHTS ALOFT WILL BE ON THE RISE
TONIGHT AND CONTINUE INTO TUESDAY AS THE DEEP ERN TROF DEPARTS AND
THE UPPER RIDGE BUILDS INTO THE AREA. THE ONLY QUESTION IS JUST
HOW WARM IT MAY GET. THE DEPTH OF MIXING VARIES ON THE MODEL
SOUNDINGS WITH THE AVERAGE AROUND 900 MB AND SOME EVEN HIGHER. IF
WE MIX HIGHER THAN 900 MB WE COULD GET A BIT WARMER THAN THE
CURRENT FORECAST OF MAINLY UPPER 80S/90. MOISTURE WILL RETURN AS
WELL GIVEN THE PERSISTENT S/SW FLOW BUT THE MODELS LOOK OVERLY
AGRESSIVE WITH THE MAGNTUDE INITIALLY FORECASTING SURFACE TDS OF
65-70 BY 00Z THURSDAY. CURRENT READINGS ACROSS THE SOUTHERN PLAINS
AND SURFACE TRAJECTORIES JUST DONT SUPPORT THAT.

GLASS

.LONG TERM...(WEDNESDAY THROUGH NEXT MONDAY)
ISSUED AT 315 PM CDT MON MAY 13 2013

THE THREAT OF THUNDERSTORMS WILL ENTER THE PICTURE ON WEDNESDAY
AFTERNOON AND CONTINUE INTO THE WEEKEND...ALTHO THE MAIN TIME
FRAMES WILL BE WED AFTERNOON-THURSDAY AND AGAIN SUNDAY/SUNDAY
NIGHT. THE MAIN BAND OF WESTERLIES WILL BE ACROSS THE NORTHERN
TIER STATES WED-THURSDAY HOWEVER THE SRN STREAM UPPER TROF WILL BE
IMPACTING THE AREA. THIS SYSTEM AND AN EAST-WEST FRONT WILL BE THE
KEY PLAYERS...WITH THE SRN SYSTEM AND PERSISTENT LOW LEVEL
SOUTHERLY FLOW RESULTING IN INCREASING/DEEPENING MOISTURE
BEGINNING LATE WED...CONTRIBUTING TO MODERATE INSTABILITY. THE
FRONT IS ANOTHER ITEM ALL TOGETHER WITH THE MODELS CONTINUING TO
DEPICT A SPREAD IN SOUTHWARD PUSH. THERE IS REASONABLE CONSENSUS
THE FRONT WILL RESIDE ACROSS NRN IL AND EXTREME NRN MO EARLY WED
EVENING WITH THE GFS/ECMWF LETTING IT SAG A BIT FURTHER SOUTH BY
THURSDAY WHILE THE NAM AND LOCAL WRF BRING THE FRONT SOUTH OF
I-70. THE MORE SRN POSITIONS MAY BE A REFLECTION OF CONVECTIVE
IMPACTS. AT THIS TIME I WILL HAVE THE HIGHEST POPS ACROSS THE NRN
THIRD OF THE CWA TAPPERED SOUTHWARD WITH AN OVERALL E/SEWD
ORIENTATION ON THURSDAY REFLECTIVE OF W/NW FLOW ALOFT.

THE OVERALL TRENDS ARE FOR THE FRONT TO RETREAT BACK NORTHWARD LATE
THURSDAY NIGHT AND INTO FRIDAY AS THE SOUTHERN STREAM SYSTEM DEPARTS
TO THE EAST. THE FLOW ALOFT BEGINS TO BUCKLE LATE FRIDAY INTO
SATURDAY AS A NEW TROF MOVES INTO THE WESTERN U.S. AND DEEPENS
LEADING TO DOWNSTREAM RIDGING THROUGH THE MS VALLEY...LESS ORGANIZED
PCPN CHANCES AND WARMER TEMPS. HOWEVER BY SUNDAY/SUNDAY NIGHT THE
WRN UPPER TROF AND ATTENDANT COLD FRONT WILL PROGRESS INTO THE MS
VALLEY WITH POTENTIALLY THE BEST THREAT OF ORGANIZED STRONG OR
GREATER THUNDERSTORMS WE HAVE SEEN THIS SPRING.

GLASS

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1206 PM CDT MON MAY 13 2013

VFR AND DRY THRU THE PERIOD. SLY WINDS BECOME SWLY TUES MORNING
AND INCREASE TO AROUND 12 KTS.

SPECIFICS FOR KSTL...VFR AND DRY THRU THE PERIOD. SWLY WINDS SHUD
BECOME SSELY EARLY THIS AFTERNOON. WINDS WILL BECOME SWLY TUES
MORNING AND INCREASE TO 12 KTS WITH GUSTS IN THE 20 KT RANGE LATE
IN THE MORNING AND INTO THE AFTERNOON.

TILLY

&&

.CLIMATE...
ISSUED AT 1047 AM CDT MON MAY 13 2013

RECORD HIGHS

              5/14

ST LOUIS    91 (1931)

COLUMBIA    90 (1987)

QUINCY      94 (1915)


&&

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

$$

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