Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 280925
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
425 AM CDT TUE JUL 28 2015

.SHORT TERM: (THROUGH WEDNESDAY)
ISSUED AT 309 AM CDT TUE JUL 28 2015

OPPRESSIVELY HOT AND HUMID CONDITIONS WILL PERSIST TODAY BENEATH
AN UPPER LEVEL RIDGE AXIS. THE PRESENCE OF OUTFLOW BOUNDARIES
WITHIN A NEARLY UNCAPPED ATMOSPHERE HAS BEEN SUFFICIENT FOR
ISOLATED TO SCATTERED SH/TS OVER THE LAST COUPLE OF DAYS, AND
SINCE NEITHER THE AIR MASS NOR THE FORECAST H7 TEMPERATURES HAVE
CHANGED SIGNIFICANTLY FROM THE LAST FEW DAYS, A SIMILAR PCPN
SCENARIO IS EXPECTED TODAY. GENERALLY FOLLOWED H7 TEMPERATURES AS
A PROXY FOR CAPPING TO DETERMINE PLACEMENT OF SCHC POPS.

A LOW PRESSURE SYSTEM MOVING ALONG THE US/CANADA BORDER WILL SEND
A COLD FRONT THROUGH THE PLAINS TODAY/TONIGHT. SINCE THE UPPER
FLOW BECOMES NORTHWESTERLY BEHIND THE LOW PRESSURE SYSTEM IN
RESPONSE TO A BUILDING RIDGE OVER THE WEST COAST, ODDS ARE GOOD
THAT THIS COLD FRONT WILL MOVE THROUGH MO/IL ON WED/WED NIGHT AND
BRING RELIEF FROM THE RECENT HEAT/HUMIDITY FOR A COUPLE OF DAYS.
SH/TS MAY ACCOMPANY THE FRONT ON WEDNESDAY BUT PCPN SHOULD TAPER
OFF ACROSS THE CWA BY WED NIGHT.

KANOFSKY

.LONG TERM: (THURSDAY THROUGH MONDAY)
ISSUED AT 309 AM CDT TUE JUL 28 2015

THURSDAY AND FRIDAY LOOK SPECTACULARLY DRIER AND LESS HUMID WITHIN
THE POST-FRONTAL AIR MASS. THE BUILDING RIDGE OVER THE WESTERN
CONUS WILL KEEP NW FLOW IN PLACE OVER MO/IL THROUGH THE WEEKEND.
BOTH THE 12Z AND 00Z RUNS OF THE GFS/ECMWF DISAGREE ON THE EXTENT
OF THE NW FLOW, HOWEVER-- THE EC IS FARTHER NORTH WITH A LOW
PRESSURE SYSTEM IN CANADA WHICH KEEPS THE FLOW NEARLY QUASIZONAL
BUT THE GFS IS FARTHER SOUTH WITH THE LOW IN CANADA WHICH LEADS TO
A SHARPER NW FLOW SOLUTION. A COUPLE OF DISTURBANCES MOVING
THROUGH THE FLOW COULD SUPPORT PERIODS OF SH/TS LATE THIS WEEKEND
AND/OR EARLY NEXT WEEK, BUT SUCH FEATURES ARE TOO POORLY RESOLVED
THIS FAR IN ADVANCE TO HAVE CONFIDENCE IN POPS GREATER THAN SCHC-
CHC. TEMPERATURES WILL MODERATE TO SEASONABLY WARM UPPER 80S TO
LOWER 90S.

KANOFSKY

&&

.AVIATION:  (FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1048 PM CDT MON JUL 27 2015

ONLY ISOLATED TSRA REMAINS ACROSS SOUTHEAST MO. SHORT WAVE LIFTING
NORTH AS THE RIDGE BUILDS ACROSS THE REGION. ONE WOULD THINK THIS
WOULD PRODUCE A MOSTLY DRY DAY TUESDAY AS ANY DEVELOPMENT SHOULD
BE WELL NORTH OF MO. HOWEVER MODELS CONTINUE TO FIRE UP SCATTERED
TSRA IN THE AFTERNOON MAINLY ACROSS EASTERN MO AND WESTERN IL. IT
WILL NOT TAKE MUCH IN THIS HOT, HUMID, UNSTABLE AIR MASS. A
VICINITY FOR UIN, SUS AND CPS WOULD WILL BE THE BEST I CAN DO FOR
NOW. EXPECT SOME MORNING FOG AGAIN AS WELL.

SPECIFICS FOR KSTL: ISOLATED TSRA HAS PUSHED SOUTH AND SHOULD STAY
THERE. WHAT LIFT THAT IS LEFT APPEARS TO BE BETTER ACROSS
SOUTHEAST MO. MODELS AGAIN DEVELOP ISOLATED TSRA ACROSS EASTERN MO
FOR TUESDAY AFTERNOON. WILL THROW IN A VICINITY TO COVER.

JPK

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...EXCESSIVE HEAT WARNING UNTIL 9 PM CDT THIS EVENING FOR BOONE MO-
     CALLAWAY MO-COLE MO-CRAWFORD MO-FRANKLIN MO-GASCONADE MO-
     IRON MO-JEFFERSON MO-LINCOLN MO-MADISON MO-MONITEAU MO-
     MONTGOMERY MO-OSAGE MO-REYNOLDS 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 THIS EVENING FOR AUDRAIN MO-KNOX MO-
     LEWIS MO-MARION MO-MONROE MO-PIKE MO-RALLS MO-SHELBY MO.

IL...EXCESSIVE HEAT WARNING UNTIL 9 PM CDT THIS EVENING FOR CALHOUN
     IL-JERSEY IL-MADISON IL-MONROE IL-RANDOLPH IL-ST. CLAIR IL.

     HEAT ADVISORY UNTIL 9 PM CDT THIS EVENING FOR ADAMS IL-BOND IL-
     BROWN IL-CLINTON IL-FAYETTE IL-GREENE IL-MACOUPIN IL-MARION
     IL-MONTGOMERY IL-PIKE IL-WASHINGTON IL.

&&

$$

WFO LSX


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