Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 281752
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1252 PM 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 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1241 PM CDT TUE JUL 28 2015

PRIMARY CONCERN FOR THIS AFTERNOON IS THUNDERSTORM TRENDS. AT THIS
TIME, IT STILL LOOKS LIKELY THAT THERE WILL BE WIDELY SCATTERED
THUNDERSTORMS OVER MUCH OF EASTERN MISSOURI AND WESTERN ILLINOIS
THIS AFTERNOON. TIMING AND COVERAGE IS YET UNCERTAIN...BUT AM
BEGINNING TO NOTICE CUMULUS STARTING TO FORM OVER PARTS OF THE
OZARKS WHICH DOES BODE WELL FOR THUNDERSTORM DEVELOPMENT. STORMS
COULD BE STRONG WITH GUSTY WINDS AND VERY HEAVY RAIN, REDUCING THE
VISIBILITY TO IFR CONDITIONS. OTHERWISE EXPECT VFR FLIGHT
CONDITIONS TO CONTINUE. A COLD FRONT WILL MOVE INTO THE AREA
OVERNIGHT WHICH WILL BRING ANOTHER CHANCE OF THUNDERSTORMS WITH
POTENTIAL FOR LOWERED CONDITIONS AS WELL AS LOCALLY GUSTY WINDS.

SPECIFICS FOR KSTL:

PRIMARY CONCERN CONTINUES TO BE THE POSSIBILITY FOR THUNDERSTORMS
THIS AFTERNOON AT THE TERMINAL. THINK STORMS WILL DEVELOP OVER THE
EASTERN OZARKS LATER THIS AFTERNOON, WITH OUTFLOW BOUNDARIES
MOVING NORTH INTO THE METRO AREA TO PRODUCE ADDITIONAL STORMS
BETWEEN 21-00Z. TIMING AND COVERAGE IS STILL UNCERTAIN THOUGH SO I
DID NOT WANT TO HIT IT HARDER THAN VCTS AT THIS TIME. STORMS
SHOULD DISSIPATE DURING THE EARLY EVENING, AND EXPECT VFR
CONDITIONS TO PREVAIL FOR THE REST OF THE NIGHT INTO WEDNESDAY
MORNING. THERE WILL BE ANOTHER CHANCE OF STORMS DURING THE LATE
MORNING/AFTERNOON AS A COLD FRONT MOVES THORUGH THE AREA.

CARNEY

&&

.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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