Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 050453
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1153 PM CDT SAT JUL 4 2015

.UPDATE:
ISSUED AT 918 PM CDT SAT JUL 4 2015

FORECAST ON TRACK AND ONLY NEED SLIGHT ADJUSTMENTS. THICKER HIGH
LEVEL CLOUDINESS SOUTHEAST OF STL METRO ASSOCIATED WITH A MATURE
STORM SYSTEM CENTERED OVER WESTERN TN THAT WILL CONTINUE TO TRACK
EASTWARD OVERNIGHT AND WILL PULL THIS WITH IT, LEAVING BEHIND
CLEAR SKIES, IF NOT CLEAR ALREADY. A PERSISTENCE FORECAST
OTHERWISE SEEMS VERY MUCH IN ORDER WITH TEMPS DROPPING INTO THE
60S ONCE AGAIN WITH PATCHY FOG DEVELOPING IN MANY AREAS TOWARDS
MORNING.

TES

&&

.SHORT TERM:  (THROUGH LATE TONIGHT)
ISSUED AT 330 PM CDT SAT JUL 4 2015

TRANQUIL NIGHT ON TAP FOR THE AREA WITH PLEASANT EARLY JULY
TEMPERATURES. HIGH PRESSURE SYSTEM CENTERED IN THE OHIO VALLEY
WILL SLOWLY RETREAT EAST OVERNIGHT WITH LIGHT SOUTHEAST SURFACE
WINDS DEVELOPING. THE CURRENT DIURNAL CU WILL DISSIPATE WITH THE
LOSS OF HEATING, WHILE SOME CIRRUS WILL SPREAD INTO THE AREA
AHEAD OF A PLAINS SHORTWAVE. OVERALL SKIES WILL RANGE FROM CLEAR
TO PARTLY CLOUD AND A TAD HAZY, WITH SOME PATCY FOG DEVELOPMENT
OVERNIGHT.

GLASS

.LONG TERM:  (SUNDAY THROUGH NEXT SATURDAY)
ISSUED AT 330 PM CDT SAT JUL 4 2015

HIGH PRESSURE OVER THE OHIO VALLEY WILL CONTINUE TO RETREAT EAST
WHILE SURFACE PRESSURES BEGIN TO FALL ACROSS THE PLAINS, AND THIS
WILL LEAD TO INCREASING SOUTHERLY LOW LEVEL FLOW AND ATTENDANT
WARM ADVECTION AND MOISTURE RETURN SUNDAY INTO SUNDAY NIGHT.
ACCORDINGLY, THE HIGH TEMPERATURES ON SUNDAY WILL BE WARMER AND
CLOSER TO AVERAGE. PRECIPITATION CHANCES DURING THIS PERIOD APPEAR
TO BE FOCUSED WELL TO OUR NORTHWEST ACROSS THE NORTHERN PLAINS
INTO THE UPPER MS VALLEY.

THE DRY PERIOD HOWEVER WILL COME TO AN END ON MONDAY AND ESPECIALLY
MONDAY NIGHT INTO WEDNESDAY. TROFFING ALOFT WILL EVOLVE ACROSS THE
NORTHERN TIER OF THE CONUS AS A SERIES OF SHORT WAVE TROFS DIG
EAST SOUTHEAST FROM WESTERN CANADA. THIS WILL ULTIMATELY BRING A
NORTHEAST-SOUTHWEST ORIENTED COLD FRONT INTO THE AREA. THE MODELS
DIFFER SOME ON TIMING WITH THE NAM THE SLOW OUTLIER AND THE MORE
PROGRESSIVE GFS/SREF/ECMWF SOLUTIONS FOLLOWED - BRINGING THE
FRONT INTO NORTHWEST MO ON MONDAY AFTERNOON AND INTO NORTHERN
SECTIONS OF THE CWA MONDAY NIGHT WITH A WAVY FRONTAL BOUNDARY FROM
SOUTHERN ILLINOIS INTO SOUTHEAST MISSOURI BY TUESDAY AFTERNOON.
THE AREA WELL AHEAD OF THE FRONT FROM CENTRAL INTO EAST CENTRAL MO
AND SOUTHWEST ILLINOIS SHOULD SEE ANOTHER WARM DAY ON MONDAY WITH
HIGHS AROUND 90, WHILE SHOWERS AND THUNDERSTORMS WILL MOVE INTO
NORTHWEST SECTIONS OF THE CWA BY EARLY MONDAY EVENING. A SEASONABLY
MOIST AIR MASS WITH SURFACE DEW POINTS IN THE UPPER 60S/LOWER 70S
AND H85 DEW POINTS IN THE TEENS ALONG WITH FAVORABLY DEEP LOW
LEVEL CONVERGENCE WILL SUPPORT WIDESPREAD SHOWERS AND THUNDERSTORMS
ALONG AND AHEAD OF THE FRONT AS IT PROGRESSES SOUTHEASTWARD. GIVEN
THIS SCENARIO AND THE AFOREMENTIONED MOISTURE CONTENT /PWS NEAR 2
INCHES/ AND OVERALL SLOW WIND SPEEDS ALOFT, WE COULD SEE ANOTHER
WIDESPREAD 2-4 INCH MULTI-DAY RAINFALL EVENT.

WEAK QUASI-ZONAL FLOW ALOFT WILL PERSIST DURING THE LATER HALF OF
NEXT WEEK WITH EMBEDDED WEAK DISTURBANCES. THESE COMBINED WITH THE
FRONT WAVERING ABOUT THE AREA WILL RESULT IN AN UNSETTLED PATTERN
WITH CONTINUED THUNDERSTORM CHANCES INTO AT LEAST LATE FRIDAY.

GLASS

&&

.AVIATION:  (FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1141 PM CDT SAT JUL 4 2015

MVFR VSBYS ARE SPREADING ACROSS PARTS OF EAST CENTRAL AND
SOUTHEAST MISSOURI. SOME IFR VSBYS BEING REPORTED IN THE STL METRO
AREA AT THIS TIME AS WELL...MIGHT BE SMOKE FROM FIREWORKS. THIS
SMOKE MAY DISSIPATE SOMEWHAT ALLOWING VSBYS TO IMPROVE INTO MVFR
CATEGORY...OR FOG/HAZE MAY THICKEN AS SMOKE DISSIPATES AND VSBYS
MAY CHANGE LITTLE OR EVEN WORSEN. AM NOT VERY CONFIDENT EITHER WAY
AT THIS TIME. REGARDLESS...SHOULD SEE IMPROVEMENT AFTER DAYBREAK
AND INCREASING SOUTHEAST FLOW WILL HELP TO CLEAR LINGERING FOG AND
HAZE. THE REMAINDER OF SUNDAY SHOULD BE VFR.

SPECIFICS FOR KSTL:

HAZE AND SMOKE FROM FIREWORKS HAS LOWERED VSBY BELOW 3SM AT THIS
TIME. AM UNSURE HOW MUCH IMPROVEMENT THERE WILL BE. SMOKE MAY
DISSIPATE SOMEWHAT ALLOWING VSBYS TO IMPROVE INTO MVFR
CATEGORY...OR FOG/HAZE MAY THICKEN AS SMOKE DISSIPATES AND VSBYS
MAY CHANGE LITTLE OR EVEN WORSEN. AM NOT VERY CONFIDENT EITHER WAY
AT THIS TIME. REGARDLESS...SHOULD SEE IMPROVEMENT AFTER DAYBREAK
AND INCREASING SOUTHEAST FLOW WILL HELP TO CLEAR LINGERING FOG AND
HAZE. THE REMAINDER OF SUNDAY SHOULD BE VFR.

CARNEY

&&

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

$$

WFO LSX


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