778 
FXUS63 KLSX 251125
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
525 AM CST MON FEB 25 2013

.SHORT TERM...
ISSUED AT 341 AM CST MON FEB 25 2013
(TODAY)

CLOSED LOW WILL MOVE ACROSS NORTHERN TEXAS AND INTO SOUTHEAST 
OKLAHOMA TODAY. MEANWHILE...THE ATTENDANT SURFACE LOW WILL DEEPEN AS 
IT MOVES NORTHEAST FROM CENTRAL TEXAS TO THE ARKLATEX REGION BY 00Z. 
EAST WIND TO INCREASE AS PRESSURE GRADIENT TIGHTENS ACROSS THE 
REGION. A TYPICAL THICKENING AND LOWERING CLOUD FORECAST AS TOP DOWN 
SATURATION BEGINS IN ADVANCE OF THE STORM SYSTEM. TEMPERATURES TO BE 
FAIRLY SIMILAR TO YESTERDAY AS INCREASING CLOUD COVER SHOULD OFFSET 
SLIGHTLY WARMER ATMOSPHERE AND START TO THE DAY.

CARNEY

&&

.LONG TERM...
ISSUED AT 341 AM CST MON FEB 25 2013
(TONIGHT THROUGH SUNDAY)

PRIMARY FOCUS CONTINUES TO BE THE IMPENDING WINTER STORM TONIGHT.  
WHILE THE MASS FIELDS IN THE NCEP MODEL SUITES ARE VERY CLOSE WITH 
RESPECT TO THE POSITION AND TRACK OF THIS STORM...THERMAL 
SHENANIGANS CONTINUE ON A RUN-TO-RUN BASIS.  THE GENERAL IDEA 
REMAINS THE SAME: AS THE LOW MOVES INTO ARKANSAS THE OVER ALL
TROF STRUCTURE WILL BECOME NEGATIVELY TILTED OVERNIGHT AND THE
STORM WILL BEGIN MOVING NORTHEAST...CROSSING THE BOOT HEEL TUESDAY
AROUND 18Z AND INTO THE OHIO VALLEY BY 00Z WEDNESDAY.
PRECIPITATION WILL OVERSPREAD THE AREA FROM THE SOUTHWEST THIS
EVENING AND IT SHOULD BE RAINING/SNOWING OVER THE ENTIRE AREA BY
MIDNIGHT. STRONG INDICATIONS OF A TROWAL ON BOTH THE GFS AND NAM
AS WARM AIR WRAPS AROUND THE LOW LEVEL CIRCULATION. 850MB
ISOTHERMS HAVE A VERY PRONOUNCED WESTWARD KINK AS THE STORM PASSES
ACROSS SOUTHEAST MISSOURI. THE NAM IS COOLER THAN THE GFS...AND
THE ECMWF IS COOLER STILL. HAVE TRIED TO USE A COMBINATION OF THE
THREE TO FORECAST PRECIP TYPES AND CHANGE OVER TIMES. MODEL
SOUNDINGS INDICATE AN ISOTHERMAL LAYER RIGHT AROUND ZERO DURING
THE EVENING STRETCHING FROM COLUMBIA UP TO QUINCY. THE SOUTHERN
END OF THAT LINE DOES HAVE A WARM WEDGE OF AROUND 2C BELOW 850MB
WHICH INDICATES THE PRECIP SHOULD EITHER START AS LIQUID...OR
PERHAPS A SLEET/SNOW MIX. IT'S STILL UNCLEAR HOW LONG IT WILL TAKE
FOR THE PRECIP TO BECOME ALL SNOW...OR HOW FAR EAST THE RAIN-SNOW
LINE WILL PROGRESS OVERNIGHT. AS MENTIONED EARLIER...THE GUIDANCE
JUST CAN'T SEEM TO COME TO A CONSENSUS. NEEDLESS TO SAY...THERE
WILL LIKELY BE A VERY TIGHT GRADIENT BETWEEN AREAS THAT GET LITTLE
OR NO SNOW...AND AREAS THAT GET WARNING CRITERIA SNOW.
REGARDLESS...IT LOOKS LIKE AREAS FROM COLUMBIA TO QUINCY AND
POINTS WEST WILL GET 6 TO 8 INCHES OF SNOW WITH LOCALLY HIGHER
AMOUNTS. WILL THEREFORE ISSUE A WINTER STORM WARNING WITH A BUFFER
OF WINTER WEATHER ADVISORY ONE ROW OF COUNTIES EAST. EXPECT THE
REMAINDER OF THE AREA NOT TO GET ENOUGH SNOW TO JUSTIFY HEADLINES.
PRECIPITATION SHOULD TAPER OFF TUESDAY AFTERNOON...BUT ANOTHER
SHORTWAVE WILL DIP IN BEHIND THE THE STORM TUESDAY NIGHT AND MOVE
RAPIDLY EAST INTO THE OHIO VALLEY BY WEDNESDAY NIGHT. LOOKS LIKE
THERE COULD BE A ANOTHER QUICK SHOT OF SNOW WITH THIS SECONDARY
SHORTWAVE. MODEL QPF IS LIGHT...GENERALLY LESS THAN 0.1 INCH SO AM
NOT EXPECTING TO NEED ADDITIONAL HEADLINES AT THIS TIME.

THE UPPER LEVEL PATTERN BECOMES HIGHLY AMPLIFIED IN THE WAKE 
TUESDAY'S STORM.  A DEEP LONGWAVE TROF WILL DIG IN OVER THE EASTERN 
SEABOARD WITH A STRONG RIDGE OVER THE ROCKIES.  THIS WILL KEEP US IN 
NORTHERLY FLOW ALOFT.  THE REMAINDER OF THE FORECAST LOOKS COLD WITH 
TEMPERATURES RUNNING ABOUT 10 DEGREES BELOW NORMAL THROUGH THE 
PERIOD.  WEATHER SHOULD ALSO BE DRY WITH THE EXCEPTION OF SOME 
FLURRIES AS ADDITIONAL SHORTWAVES DIVE SOUTH ACROSS THE AREA IN THE 
NORTHERLY FLOW.

CARNEY

&&

.AVIATION...
ISSUED AT 517 AM CST MON FEB 25 2013

WINTER STORM APPROACHING FROM THE SOUTHWEST WILL CAUSE CEILINGS TO
LOWER THROUGHOUT THE DAY...WITH PRECIPITATION SPREADING FROM
SOUTH TO NORTH ACROSS THE REGION THIS EVENING. EXPECT RAIN TO MIX
AND CHANGE TO SNOW AT COLUMBIA AND QUINCY OVERNIGHT...WITH ONLY
RAIN FOR ST. LOUIS METRO TERMINALS. NORTHEAST WIND WILL INCREASE
AS PRESSURE GRADIENT TIGHTENS OVER THE REGION. COULD SEE GUSTS TO
30KTS. IFR CEILING AND VISIBILITY EXPECTED WITH HEAVIEST BAND OF
PRECIPITATION LATE THIS EVENING THROUGH TUESDAY MORNING.

SPECIFICS FOR KSTL...

THICKENING AND LOWERING CEILING EXPECTED TODAY...WITH RAIN MOVING
INTO THE TERMINAL COMPLEX THIS EVENING. CONDITIONS TO LOWER TO IFR
WITH HEAVIEST PRECIPITATION BETWEEN 06Z AND 15Z. NORTHEAST WIND TO
INCREASE TO NEARLY 20KT WITH GUSTS APPROACHING 30KT. WIND TO
DECREASE BRIEFLY ON TUESDAY AS LOW PRESSURE MOVES JUST TO THE
SOUTH OF THE TERMINAL.

CVKING

&&

.PRELIMINARY POINT TEMPS/POPS...
SAINT LOUIS     45  34  37  30 /  10 100  80  50 
QUINCY          40  29  32  26 /   0 100 100  60 
COLUMBIA        42  31  33  26 /  20 100  80  50 
JEFFERSON CITY  45  32  34  27 /  40 100  80  50 
SALEM           47  36  41  31 /   5 100  80  40 
FARMINGTON      49  37  41  29 /  20 100  60  30 

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST TUESDAY 
     FOR AUDRAIN MO-BOONE MO-KNOX MO-LEWIS MO-MARION MO-MONITEAU 
     MO-MONROE MO-RALLS MO-SHELBY MO.

     WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST 
     TUESDAY FOR CALLAWAY MO-COLE MO-MONTGOMERY MO-OSAGE MO-PIKE 
     MO.

IL...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST TUESDAY 
     FOR ADAMS IL-BROWN IL.

     WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST 
     TUESDAY FOR PIKE IL.

&&

$$

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