Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 270416
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1116 PM CDT SUN JUL 26 2015

.SHORT TERM:  (THROUGH LATE TONIGHT)
ISSUED AT 328 PM CDT SUN JUL 26 2015

SCATTERED THUNDERSTORMS HAVE DEVELOPED LATE THIS AFTERNOON ALONG OLD
OUTFLOW BOUNDARY.  LATEST HRRR SHOW THUNDERSTORMS CONTINUING ACROSS
SOUTHEAST MISSOURI THROUGH THE EVENING HOURS AHEAD OF A WEAK
SHORTWAVE TROUGH THAT IS CURRENTLY MOVING SOUTHEASTWARD ACROSS
NORTHERN MISSOURI.  THE RAP SHOWS THIS SHORTWAVE LIFTING OUT OF THE
AREA BY 06Z.

BRITT

.LONG TERM:  (MONDAY THROUGH NEXT SUNDAY)
ISSUED AT 328 PM CDT SUN JUL 26 2015

(MONDAY THROUGH WEDNESDAY)

MAIN CONCERN WILL BE HEAT ON MONDAY AND TUESDAY WITH HEAT INDICES OF
105 TO 110+ BY TUESDAY AFTERNOON.  HAVE EXTENDED THE CURRENT
ADVISORY OVER CENTRAL MISSOURI AND HAVE EXPANDED THE ADVISORY TO
INCLUDE THE ENTIRE CWA.  THE UPPER RIDGE WILL BUILD OVER THE REGION
WHICH WILL LIMIT THUNDERSTORMS CHANCES TO SLIGHT CHANCES BOTH DAYS.
BECAUSE OF THIS...HIGH TEMPERATURES WILL BE ABLE TO CLIMB INTO THE
90S AS 850MB TEMPERATURES CLIMB INTO THE LOW 20S.  FORECAST
SOUNDINGS SHOW MIXING UP TO 850MB ON MONDAY AND CLOSE TO 800MB ON
TUESDAY.  WITH DEWPOINTS WELL IN THE 70S GIVEN THE RECENT
RAINFALL...THIS WILL RESULT IN THE HEAT INDICES AROUND 105 ON MONDAY
AND NEAR 110 ON TUESDAY.  TEMPERATURES WILL BEGIN TO COOL DOWN BY
WEDNESDAY AS THE ECMWF/GFS SHOW A COLD FRONT MOVING SOUTHEAST ACROSS
THE CWA THROUGH THE DAY.  FORCING WILL NOT BE GREAT ALONG THE FRONT,
BUT ENOUGH TO INCLUDE A CHANCE OF THUNDERSTORMS.

(THURSDAY THROUGH NEXT SUNDAY)

STILL EXPECT THIS TO BE A COOLER PERIOD AS THE POLAR FRONT THAT
MOVED THROUGH THE AREA ON WEDNESDAY WILL STAY SOUTH OF THE AREA
BECAUSE THE UPPER FLOW BECOMING NORTHWESTERLY THROUGH THE WEEKEND.
THIS WILL BE BECAUSE OF A BUILDING UPPER HIGH IN THE SOUTHWEST AND A
TROUGH IN THE EAST.  WHILE THE GFS/ECMWF BOTH AGREE ON THE OVERALL
PATTERN CHANGE, THEY DIFFER ON JUST HOW FAST THE UPPER FLOW WILL BE
OVER THE AREA AND WHETHER A SECONDARY COLD FRONT WILL MOVE THROUGH
THE REGION NEXT SUNDAY.  THE GFS SHOWS DEPICTS SOME LIGHT QPF WITH
THIS FRONT WHEREAS THE ECMWF IS DRY THROUGH THE EXTENDED PERIOD.
FOR NOW WILL GO WITH A DRY FORECAST.  WILL ALSO GO WITH SLIGHTLY
BELOW NORMAL TEMPERATURES GIVEN 850MB TEMPERATURES IN THE UPPER
TEENS CELCIUS.

BRITT

&&

.AVIATION:  (FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1105 PM CDT SUN JUL 26 2015

ISOLATE TO SHOWERS AND THUNDERSTORMS CONTINUE TO
DEVELOP...NORTHEAST AND TO THE SOUTH OF STL. THIS MOST LIKELY FROM
SOME OUTFLOW BOUNDARIES AND SOME ISENTROPIC LIFT WITH THE 850 MB
WIND. WIND BEGINS TO BECOME MORE PARALLEL TO THE FLOW BY 06Z AND
FINISHED THE PROCESS BY 12Z. WOULD NOT BE SURPRISED TO SEE
CONTINUED SPOTTER DEVELOPMENT FOR SEVERAL HOURS YET. THE LATEST
HRRR-CR AGREES WITH THIS SCENARIO AND PLACEMENT PRETTY WELL.
PRIMARY MODELS DEVELOP SCATTERED ACTIVITY MONDAY AFTERNOON...BUT
WITH VERY LOW POPS IN THE FORECAST WILL GO WITH A DRY FORECAST.
WITH LIGHT WIND AND RECENT RAIN AT MOST LOCATIONS WILL GO WITH A
TEMPO FOR A COUPLE HOURS OF MORING FOG.

SPECIFICS FOR KSTL: ISOLATED TO WIDELY SCATTERED SHOWERS AND
THUNDERSTORMS CONTINUE IN THE AREA. DEPENDING ON LOCATION...MAY
CONTINUE THE VCTS A COUPLE MORE HOURS BEYOND 06Z. A LITTLE
CONCERNED WITH POSSIBLE FOG IN THE MORNING GIVEN RECENT RAIN. AS
USUAL THE MET GUIDANCE HITS CIG/VIS HARD WITH THE MAV VFR. WILL GO
AHEAD AND THROW IN A TEMPO FOR A COUPLE OF HOURS MONDAY MORNING.

JPK

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...HEAT ADVISORY FROM NOON MONDAY TO 9 PM CDT TUESDAY FOR AUDRAIN
     MO-CRAWFORD MO-FRANKLIN MO-GASCONADE MO-IRON MO-JEFFERSON
     MO-KNOX MO-LEWIS MO-LINCOLN MO-MADISON MO-MARION MO-MONROE
     MO-MONTGOMERY 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.

     HEAT ADVISORY UNTIL 9 PM CDT TUESDAY FOR BOONE MO-CALLAWAY MO-
     COLE MO-MONITEAU MO-OSAGE MO.

IL...HEAT ADVISORY FROM NOON MONDAY TO 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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