Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 260452
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1152 PM CDT SAT JUL 25 2015

.SHORT TERM: (TONIGHT AND SUNDAY)
ISSUED AT 348 PM CDT SAT JUL 25 2015

WILL ISSUE A FLASH FLOOD WATCH TONIGHT FOR MUCH OF NORTHEAST
MISSOURI AND WEST CENTRAL ILLINOIS AS I EXPECT A MCS TO MOVE ACROSS
THE AREA LATER THIS EVENING INTO THE OVERNIGHT HOURS.  NAM AND GFS
MASS FIELDS SEEM TO SUPPORT THE IDEA OF STRONG MOISTURE CONVERGENCE
DEVELOPING DURING THE EVENING OVER NORTHERN MISSOURI WHICH WILL
LIKELY SUPPORT THE DEVELOPMENT OF A MCS.  PROPOPATION VECTORS FAVOR
THIS MCS MOVING ACROSS NORTHERN MISSOURI BEFORE TURNING
SOUTHEASTWARD NEAR THE MISSISSIPPI RIVER LATE TONIGHT.  THIS IS
SUPPORTED BY 12Z NMM-WRF CAM. PWATS ARE VERY HIGH WITH VALUES
OVER 2.0 INCHES CONTINUING TO SUGGEST THAT RAINFALL WILL BE
POTENTIALLY HEAVY. HAVE GONE WITH A FLASH FLOOD WATCH FOR THIS
REASONING.

THE MCS WILL BE DECAYING ON SUNDAY MORNING...BUT WILL STILL INCLUDE
LIKELY POPS ON SUNDAY MORNING OVER PART OF THE AREA AS IT MOVES
SOUTHEAST.  LIKE TODAY...THE CLOUDS AND MORNING RAIN MAY TEMPER THE
RECOVERY IN TEMPERATURES WHICH WILL HAVE AN IMPACT IN WHETHER WE
WILL BE ABLE TO REACH HEAT INDEX CRITERIA.  FEEL THAT THE ONLY AREA
THAT I AM CONFIDENT IN ENOUGH AT THE MOMENT THAT WE WILL REACH
CRITERIA IS OVER CENTRAL MISSOURI. THERE WILL ALSO BE SOME POTENTIAL
FOR ADDITIONAL SCATTERED THUNDERSTORMS AT THE ATMOSPHERE BECOMES
UNCAPPED AND UNSTABLE DURING THE AFTERNOON.

BRITT

.LONG TERM:  (SUNDAY THROUGH NEXT SATURDAY)
ISSUED AT 348 PM CDT SAT JUL 25 2015

(SUNDAY NIGHT THROUGH TUESDAY)

THIS WILL BE A WARM PERIOD AS THE SURFACE FRONT REMAINS WELL TO THE
NORTH AND HIGH TEMPERATURES CLIMB INTO THE LOW-MID 90S.  THE
DEWPOINTS WILL BE WELL INTO THE 70S ALLOWING HEAT INDICES TO CLIMB
ABOVE 100 EACH DAY. WILL LIKELY NEED TO EXTEND AND EXPAND THE HEAT
ADVISORY DURING THIS PERIOD. RAIN CHANCES DO NOT LOOK AS HIGH AS AN
UPPER HIGH BUILDS OVER THE AREA.

(WEDNESDAY THROUGH SATURDAY)

ECMWF AND GFS ARE IN RELATIVELY GOOD AGREEMENT THAT A COLD FRONT
WILL MOVE THROUGH THE AREA ON WEDNESDAY AS THE UPPER PATTERN BEGINS
TO AMPLIFY OVER THE COUNTRY.  WILL CARRY A CHANCE OF SHOWERS AND
THUNDERSTORMS WITH THE PASSAGE OF THE COLD FRONT ON WEDNESDAY, BUT
THEN GO DRY AS NORTHWESTERLY UPPER FLOW SETS UP AS LARGE HIGH SETS
UP OVER THE WESTERN CONUS AND TROUGH DIGS IN THE EAST.  WARMEST DAY
WILL BE AHEAD OF THE FRONT ON WEDNESDAY, BUT THEN THEY WILL FALL
BACK SLIGHTLY BELOW NORMAL FOR THE REST OF THE PERIOD.

BRITT

&&

.AVIATION:  (FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1144 PM CDT SAT JUL 25 2015

CURRENT PRECIPITATION TRENDS ARE POINTING MORE TOWARD CENTRAL
MO..ALONG THE WEAK FRONT AND MORE UNSTABLE ARI. THUS HAVE REMOVED
THE TEMPO AT UIN AND MOVED IT TO COU. MODELS ARE ALL HIGH ON
DEVELOPING SHOWERS AND STORMS THIS AFTERNOON. MOIST UNSTABLE AIR
IN PLACE BUT WONDERING ABOUT ANY UPPER AIR SUPPORT AT THE SHORT
WAVE MOVES EAST AND SOME APLIFICATION OF THE RIDGE TAKES PLACE.
WILL THROW IN VCTS FOR THE LATE AFTERNOON.

SPECIFICS FOR KSTL: UNDERTAINTY STILL EXISTS IF THE SHOWERS AND
STORMS OVER NW MO WILL MAKE IT TO STL. CURRENT TRACK MAKES COU
LOOK LIKE A BETTER TARGET IN THE SHORT TERM. WILL CONTINUE THE
VCTS. MODELS ALL WANT TO DEVELOP MORE RAIN AFTER 18Z. MOIST
UNSTABLE AIR MASS IN PLACE BUT UPPER SUPPORT WILL LIKELY BE GONE.
WEAK BOUNDARIES WILL LIKELY BE THE TRIGGER POINTS. VCTS FOR LATE
AFTERNOON IS THE BEST FORECAST FOR NOW.

JPK

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...FLASH FLOOD WATCH UNTIL 7 AM CDT SUNDAY FOR AUDRAIN MO-BOONE MO-
     CALLAWAY MO-KNOX MO-LEWIS MO-LINCOLN MO-MARION MO-MONROE MO-
     MONTGOMERY MO-PIKE MO-RALLS MO-SHELBY MO.

     HEAT ADVISORY FROM NOON TO 9 PM CDT SUNDAY FOR BOONE MO-CALLAWAY
     MO-COLE MO-MONITEAU MO-OSAGE MO.

IL...FLASH FLOOD WATCH UNTIL 7 AM CDT SUNDAY FOR ADAMS IL-BROWN IL-
     PIKE IL.

&&

$$

WFO LSX



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