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000
FXUS63 KLSX 131716
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1216 PM CDT THU JUN 13 2013

.SHORT TERM...(THROUGH LATE THIS AFTERNOON)
ISSUED AT 259 AM CDT THU JUN 13 2013

COLD FRONT WILL MOVE SOUTHEAST OF THE CWA BY SUNRISE.  THERE IS AN
AREA OF BROKEN-OVERCAST LOW CLOUDS CURRENTLY OVER NORTHERN MO AND
WEST CENTRAL IL THAT IS MOVING SOUTHEAST.  CURRENT THINKING IS THAT
THESE CLOUDS WILL MOVE ACROSS THE AREA EARLY THIS MORNING...BUT THEN
SKIES WILL TURN PARTLY CLOUDY ONCE LOW LEVEL MIXING ENSUES LATER
THIS MORNING.  WILL STICK CLOSE TO GOING HIGHS WHICH ARE CLOSE TO
MOS GUIDANCE AND SUPPORTED BY MIXING DOWN 850MB TEMPERATURES.

BRITT

.LONG TERM...(TONIGHT THROUGH TUESDAY)
ISSUED AT 259 AM CDT THU JUN 13 2013

NORTHWEST FLOW ALOFT AND SURFACE HIGH PRESSURE WILL DOMINATE THE
WEATHER TONIGHT THROUGH FRIDAY NIGHT.  THIS WILL CONTINUE TO PROVIDE
US WITH COOLER AND DRIER AIR THAN WE`VE EXPERIENCED THE PAST COUPLE
OF DAYS.  TEMPERATURES WILL BE NEAR NORMAL THROUGH THIS PERIOD WITH
HIGHS IN THE LOW TO MID 80S AND LOWS GENERALLY IN THE LOW TO MID
60S.  THERE MAY BE SOME ISOLATED SHOWERS OR SPRINKLES LATE TONIGHT
OR EARLY FRIDAY MORNING OVER PARTS OF CENTRAL AND NORTHEAST MISSOURI
AS AN 850MB TROF STARTS TO DEVELOP OVER THE PLAINS WHICH FORCES A
WEAK LOW LEVEL JET TO FORM OVER WESTERN MISSOURI/EASTERN KANSAS.  IT
LOOKS LIKE ANY SHOWERS THAT ARE ABLE TO FORM WILL BE UNDER THE UPPER
RIDGE THO...SO THEY`LL BE WEAK...TRANSIENT...AND SHORT LIVED.

THE UPPER LEVEL RIDGE OVER THE PLAINS WILL BEGIN TO FLATTEN FRIDAY
NIGHT AS AN UPPER LOW CURRENTLY OVER MEXICO ROUNDS THE WESTERN SIDE
OF THE RIDGE AND GETS DRAWN UP INTO THE MID-LATITUDE WESTERLIES.
CURRENT INDICATIONS ARE THAT THE LOW WILL BE NEAR THE NORTH
TEXAS/NEW MEXICO BORDER BY 06Z SATURDAY.  THE WEAKENING RIDGE
COMBINED WITH ANOTHER HIGHER LATITUDE WAVE OVER THE DAKOTAS WILL
ALLOW THE LOW LEVEL JET TO KICK UP OVER THE EASTERN PLAINS AND THE
MIDWEST.  IT LOOKS LIKE THE JET WILL FOCUS OVER EASTERN NEBRASKA AND
IOWA...BUT THE MODEL CONSENSUS SHOWS A DECENT AMOUNT OF LOW LEVEL
MOISTURE CONVERGENCE LATE FRIDAY NIGHT ACROSS NORTHEAST MISSOURI
INTO WEST CENTRAL ILLINOIS SO THE CURRENT CHANCE POPS STILL LOOK
VALID...HAVE PUSHED POPS BACK TO AFTER 06Z THO.

THE SOUTHERN LOW GETS ABSORBED INTO THE MID-LATITUDE FLOW SATURDAY.
UPPER LEVEL FLOW BECOMES ZONAL OVER THE MID-MISSISSIPPI VALLEY AS A
RESULT.  THERE SHOULD BE PLENTY OF DEEP MOISTURE AVAILABLE FOR
THUNDERSTORMS WITH SOUTH-SOUTHWESTERLY LOW LEVEL FLOW BRINGING
HIGHER DEWPOINTS UP FROM THE GULF OF MEXICO.  HOWEVER...FORCING MAY
BE AN ISSUE.  NAM AND GFS BRING A WEAK FRONT INTO IOWA...BUT IT
NEVER MAKES IT DOWN AS FAR AS OUR AREA.  THEREFORE DAYTIME
CONVECTION ON SATURDAY MAY BE DRIVEN BY OUTFLOW BOUNDARIES FROM
CONVECTION FURTHER NORTH.  STORMS MAY BE MORE ORGANIZED SATURDAY
NIGHT...ESPECIALLY ACROSS THE NORTHERN CWFA AS A SHORTWAVE MOVES
OVER THE AREA AND A WEAK LOW LEVEL JET FOCUSES ON NORTHERN
MISSOURI.  HAVE KEPT LIKELY POPS UP THERE SATURDAY NIGHT FOR THIS
REASON.  RAIN ON SUNDAY STILL LOOKS PRETTY LIKELY AS OUTFLOWS FROM
SATURDAY NIGHT`S CONVECTION BOUNCE AROUND THE AREA.  HOWEVER TIMING
AND STRENGTH OF CONVECTION IS DIFFICULT TO DETERMINE AT THIS TIME.

ZONAL PATTERN BEGINS TO AMPLIFY MONDAY AS A SHORTWAVE DIPS ACROSS
THE UPPER MIDWEST INTO THE GREAT LAKES.  THE GFS IS LOUSY WITH
APPARENT GRID SCALE CONVECTIVE FEEDBACK OVER THE EASTERN PLAINS
MONDAY MORNING...BUT THE ECMWF DOESN`T APPEAR TO BE SUFFERING FROM
THIS PROBLEM.  REGARDLESS...BOTH MODELS TELL A SIMILAR TALE.  THE
AMPLIFYING PATTERN DRAGS A COOLER AND DRIER AIRMASS OUT OF CANADA
INTO THE GREAT PLAINS.  THE COLD FRONT AHEAD OF THIS AIRMASS DRIFTS
THROUGH MONDAY. WHILE IT ISN`T VERY STRONG...THE FRONT SHOULD SERVE
AS A FOCUS FOR CONVECTION MONDAY...AND THE DRY CANADIAN AIRMASS
BUILDS ACROSS THE REGION TUESDAY BRINGING AN END TO THE PRECIP.

CARNEY

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1207 PM CDT THU JUN 13 2013

AN AREA OF MVFR CIGS HAS BEEN FAIRLY PERSISTENT OVER METRO AREA
TAF SITES SO FAR TODAY...THOUGH EXPECT THE GENERAL SOUTHWARD
MOTION COMBINED WITH DAYTIME HEATING TO RESULT IN SCT VFR CIGS
SHORTLY AFTER THE BEGINNING OF THE FORECAST PERIOD. THERE MAY BE
SOME DIURNAL CU LINGERING ACROSS THE AREA DURING THE
AFTERNOON...WHICH SHOULD DISSIPATE AFTER SUNSET. OTHERWISE...DRY
CONDITIONS ARE EXPECTED FOR THE DURATION OF THE FORECAST...WITH
WINDS GRADUALLY SHIFTING TO THE EAST OVERNIGHT AND SOUTHEAST BY
LATE FRIDAY MORNING.

SPECIFICS FOR KSTL...
EXPECT MVFR CIGS TO IMPROVE TO SCT VFR SOON AFTER THE BEGINNING OF
THE FORECAST PERIOD...WITH ANY LINGERING CU DISSIPATING AFTER
SUNSET. DRY VFR CONDITIONS ARE EXPECTED THEREAFTER...WITH WINDS
VEERING TO THE EAST AND EVENTUALLY SOUTHEAST BY FRIDAY MORNING.

JP

&&

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

$$

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