Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 271748
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1248 PM CDT MON JUL 27 2015

.SHORT TERM:  (THROUGH LATE THIS AFTERNOON)
ISSUED AT 355 AM CDT MON JUL 27 2015

CONVECTION JUST REFUSES TO DIE OVER THE CWA, WITH HIT AND MISS
ECHOES SHOWING UP THROUGHOUT THE PREDAWN HOURS IN A BROAD BAND ALONG
THE MISSISSIPPI RIVER.  LARGEST AND MOST PERSISTENT AREA OF PRECIP
HAS BEEN OVER OUR SE COUNTIES SOUTHEAST OF STL METRO, WHERE IT
APPEARS VERY WEAK WAA INTERACTING WITH CONTINUALLY RAIN-COOLED
BOUNDARY IS ALLOWING CONVECTION TO REGENERATE.  IN SPITE OF THE
INTENSIFICATION OF THE UPPER RIDGE ACROSS THE AREA TODAY THE VARIOUS
HI-RES EXPLICIT MODELS CONTINUE TO GENERATE SPOTTY CONVECTION OVER
ALL BUT OUR FAR WESTERN COUNTIES, AND JUDGING HOW THERMAL PROFILE OF
AMS IS NEARLY UNCHANGED CARRYING SOME LOW/SLIGHT CHANCE POPS LOOKS
APPROPRIATE. HAVE PLACED HIGHEST POPS...SUCH AS THEY ARE...NEAR
WEAK SURFACE BOUNDARY SUGGESTED AT BY NAM AND RUC FROM N OF COU
THRU STL AREA.

WITHOUT FAIRLY EXTENSIVE MORNING PRECIP, TEMPERATURES ACROSS MOST OF
THE AREA SHOULD WARM NICELY TODAY. THERE IS EXTENSIVE UPSTREAM
CIRRUS FROM CONVECTION OVER THE PLAINS, BUT IT SHOULD CERTAINLY THIN
AS CONVECTION WANES AND AS THE HIGH LEVEL MOISTURE DRIFTS INTO THE
HEART OF THE RIDGE, AND HIGHS SHOULD EASILY REACH THE LOW TO MID
90S. DEWPOINTS ARE ALREADY WELL IN THE 70S, AND AFOREMENTIONED
BOUNDARY MAY ALLOW FOR FURTHER POOLING OF THIS LOW LEVEL MOISTURE
DURING THE AFTERNOON. SO, ALL PARAMETERS POINT TO A VERY STEAMY
JULY AFTERNOON, WITH THE HEAT INDEX REACHING 105 DEGREES OVER MOST
OF THE CWA. GOING HEAT ADVISORY STILL LOOKS ON THE MARK.

TRUETT

.LONG TERM:  (TONIGHT THROUGH SUNDAY)
ISSUED AT 355 AM CDT MON JUL 27 2015

(TONIGHT-WEDNESDAY)

HIGH LEVELS OF HEAT AND HUMIDITY WILL CONTINUE TONIGHT INTO
TUESDAY. HIGHS ON TUESDAY WILL LIKELY REACH THEIR HIGHEST LEVELS
DURING THIS RECENT STRETCH OF ABOVE NORMAL TEMPERATURES, WITH MID
90S COMMON ACROSS MOST OF THE CWA. HEAT INDEX VALUES SHOULD RATCHET
UP A NOTCH FROM TODAY`S LEVELS, WITH FORECAST COMBO OF HOURLY
TEMPS/DEWPOINTS YIELDING VALUES IN THE 105-110 RANGE ACROSS THE
REGION. ITS POSSIBLE THAT A FEW LOCATIONS OVER SOUTHEAST PARTS OF
THE FA COULD ONCE AGAIN PUSH HEAT INDEX VALUES AROUND 105 ON
WEDNESDAY BUT THREAT LOOKS LOW AT THIS POINT...SO WILL MAINTAIN
TIMING AND LOCATION OF CURRENT HEAT ADVISORY FOR NOW.

CONTINUED AMPLIFICATION OF UPPER RIDGE OVER THE MID MISSISSIPPI
VALLEY SUGGESTS THAT THREAT OF CONVECTION SHOULD WANE EVEN MORE
TONIGHT AND TUESDAY. HAVE MAINTAINED SOME VERY LOW POPS THIS
EVENING...PRIMARILY FOR ANY LEFT-OVER AFTERNOON ACTIVITY...AND
ALSO CONTINUED SOME LOW POPS IN OUR FAR EASTERN COUNTIES ON
TUESDAY WHERE MID LEVEL TEMPS WILL BE THEIR COOLEST.

OVERNIGHT MODEL SOLUTIONS ARE STILL BRINGING A COLD FRONT ACROSS
THE REGION LATE TUESDAY NIGHT AND INTO WEDNESDAY. BELIEVE THIS MAY
BE ONE OF THOSE SITUATIONS WHERE THERE IS A BROAD BAND OF
CONVECTION THAT IGNITES ALONG THE COLD FRONT TUESDAY NIGHT, WITH
THIS BAND OF PRECIP HAVING TROUBLE WORKING SOUTH AS COLD
FRONT...PERHAPS ENHANCED BY OUTFLOW...OUTRUNS THE UPPER LEVEL
SHORTWAVE ON WEDNESDAY. ADDITIONAL DEVELOPMENT FURTHER SOUTH ALSO
LOOKS QUESTIONABLE DURING THE DAY ON WEDNESDAY...AS CURRENT
FORECASTS INDICATE VERY LITTLE SURFACE CONVERGENCE ALONG THE
SURFACE BOUNDARY.

(THURSDAY-SUNDAY)

ALL MEDIUM RANGE SOLUTIONS SUGGEST UPPER LEVEL TROF DEVELOPING OVER
THE EASTERN CONUS DURING THE LATTER HALF OF THE WEEK, WHILE HEIGHTS
AND UPPER LEVEL RIDGE GRADUALLY RETROGRADES INTO THE WESTERN U.S.
ALTHOUGH NORTHWEST FLOW CAN BE SUBTLY STORMY, GUIDANCE SUGGESTS A
GENERALLY TRANQUIL WEATHER PATTERN FOR OUR AREA FOR THE LAST PART OF
THE WEEK. TEMPERATURES WILL BE SEASONAL, BUT THERE SHOULD BE
NOTICEABLYLESS HUMIDITY WITH DEWPOINTS PRIMARILY IN THE 60S.

DID STAY WITH MODEL CONSENSUS THAT SUGGESTS SHORTWAVE AND
ASSOCIATED COLD FRONT PRODUCING A CHANCE FOR THUNDERSTORMS BY
SUNDAY IN SOME AREAS.

TRUETT
&&

.AVIATION:  (FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1243 PM CDT MON JUL 27 2015

WARM FRONTAL BOUNDARY IS LINGERING JUST NORTH OF I70 CORRIDOR AND
SHOULD CONTINUE TO SLOWLY MOVE NORTH THIS AFTERNOON BEFORE
STALLING OUT JUST EAST OF MISSISSIPPI RIVER. IN THE
MEANTIME, DIURNAL CU WITH SOME HIGH THIN CIRRUS THROUGH THE
FORECAST PERIOD. AS FOR WINDS, TO REMAIN LIGHT AND VARIABLE BEFORE
PICKING UP A BIT FROM THE SOUTH TO SOUTHWEST FOR TAF SITES ALONG
I70 BY TUESDAY MORNING, WHILE KUIN WILL REMAIN CLOSE TO BOUNDARY
AND SEE EAST TO SOUTHEAST WINDS. ISOLATED STORMS POSSIBLE BUT HARD
TO PIN DOWN IF THEY WILL AFFECT TAF SITES, SO LEFT MENTION OUT FOR
NOW.

SPECIFICS FOR KSTL:
WARM FRONTAL BOUNDARY IS LINGERING JUST NORTH OF I70 CORRIDOR AND
SHOULD CONTINUE TO SLOWLY MOVE NORTH THIS AFTERNOON BEFORE
STALLING OUT JUST EAST OF MISSISSIPPI RIVER. IN THE
MEANTIME, DIURNAL CU WITH SOME HIGH THIN CIRRUS THROUGH THE
FORECAST PERIOD. AS FOR WINDS, TO REMAIN LIGHT AND VARIABLE BEFORE
PICKING UP A BIT FROM THE SOUTH TO SOUTHWEST BY 15Z TUESDAY.
ISOLATED STORMS POSSIBLE BUT HARD TO PIN DOWN IF THEY WILL AFFECT
METRO AREA, SO LEFT MENTION OUT FOR NOW.

BYRD
&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...HEAT ADVISORY UNTIL 9 PM CDT TUESDAY FOR AUDRAIN MO-BOONE MO-
     CALLAWAY MO-COLE MO-CRAWFORD MO-FRANKLIN MO-GASCONADE MO-
     IRON MO-JEFFERSON MO-KNOX MO-LEWIS MO-LINCOLN MO-MADISON MO-
     MARION MO-MONITEAU MO-MONROE MO-MONTGOMERY MO-OSAGE MO-PIKE
     MO-RALLS MO-REYNOLDS MO-SHELBY MO-ST. CHARLES MO-ST.
     FRANCOIS MO-ST. LOUIS CITY MO-ST. LOUIS MO-STE. GENEVIEVE
     MO-WARREN MO-WASHINGTON MO.

IL...HEAT ADVISORY UNTIL 9 PM CDT TUESDAY FOR ADAMS IL-BOND IL-BROWN
     IL-CALHOUN IL-CLINTON IL-FAYETTE IL-GREENE IL-JERSEY IL-
     MACOUPIN IL-MADISON IL-MARION IL-MONROE IL-MONTGOMERY IL-
     PIKE IL-RANDOLPH IL-ST. CLAIR IL-WASHINGTON IL.

&&

$$
WFO LSX



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