498  
FXSA20 KWBC 141638  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1237 PM EDT TUE AUG 14 2018  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
MODEL DISCUSSION (VALID FROM AUG 14 AT 0000 UTC): CONFIDENCE ON  
THE EVOLUTION OF THE FORECAST REMAINS HIGH THROUGH 96-108 HRS IN  
THE SOUTH ATLANTIC...AND THROUGH 120-144 HRS IN THE CONTINENT AND  
EASTERN PACIFIC.  
 
AN UPPER TROUGH EXITING INTO THE SOUTH ATLANTIC EARLY IN THE CYCLE  
IS IN PHASE WITH A SHORT WAVE TROUGH THAT IS CROSSING THE  
ALTIPLANO. THIS IS STIMULATING THE DEVELOPMENT OF A PAMPERO JET  
ACROSS THE CHACO...WHICH IS FORECAST TO PUSH A SURFACE COLD FRONT  
NORTHWARD TO EXTEND INTO NORTHERN BOLIVIA BY LATE TUESDAY...AND  
WEAKEN ACROSS CENTRAL PERU ON WEDNESDAY. UNDER ENHANCED DYNAMIC  
FORCING AND A MOIST POOL OF OVER 30MM OF PRECIPITABLE WATER...DEEP  
CONVECTION WILL CONTINUE DEVELOPING ACROSS MOST OF PARAGUAY WHERE  
EXPECTING ACCUMULATIONS OF 20-35MM/DAY THROUGH EARLY WEDNESDAY. AS  
THE FRONT ADVANCES ACROSS BOLIVIA...AFTERNOON AND NOCTURNAL  
CONVECTION WILL SUSTAIN MAXIMA OF 20-40MM/DAY ACROSS  
CENTRAL/NORTHERN BOLIVIA/SOUTHEASTERN PERU AND PARTS OF ACRE AND  
RONDONIA THROUGH EARLY WEDNESDAY. BY WEDNESDAY-EARLY  
THURSDAY...REMNANT CONVECTION IN THE WESTERN AMAZON WILL SUSTAIN  
MAXIMA OF 20-40MM/DAY ACROSS MOST OF CENTRAL/NORTHERN PERU AND  
WESTERN BRASIL. REMNANT CONVECTION WILL LINGER IN ECUADOR/NORTHERN  
PERU TO PRODUCE SIMILAR AMOUNTS THROUGH EARLY FRIDAY...DECREASING  
AFTER.  
 
ALSO IN NORTHERN SOUTH AMERICA...FRONTAL CONVECTION WILL ENHANCE  
TRADE WIND SHOWER CONVERGENCE IN BAHIA TO SUSTAIN MAXIMA OF  
05-10MM/DAY THROUGH EARLY WEDNESDAY...INCREASING TO 10-15MM/DAY BY  
WEDNESDAY-THURSDAY...DECREASING AFTER.  
 
BROAD TROUGH PATTERN DOMINATES THE SOUTHEASTERN PACIFIC. THIS WILL  
INTERACT WITH A SUBTROPICAL MOISTURE CONNECTION TO SUSTAIN  
MODERATE PRECIPITATION IN SOUTHERN CHILE EARLY IN THE CYCLE.  
THROUGH EARLY THURSDAY...EXPECTING ACCUMULATIONS IN THE ORDER OF  
20-35MM/DAY MOSTLY IN AYSEN. ACCUMULATIONS WILL DECREASE TO MAXIMA  
OF 15-20MM/DAY BY THURSDAY-FRIDAY WHILE FOCUSING ACROSS LOS  
LAGOS/NORTHERN AYSEN. ALSO ON FRIDAY...A COLD AIR MASS IS FORECAST  
TO ARRIVE INTO EXTREME SOUTHERN CHILE ACCOMPANIED BY BRISK  
WESTERLIES AND SHALLOW COLD-CUMULUS. THIS WILL SUSTAIN SNOWFALL  
ACCUMULATIONS OF 03-05CM/DAY.  
 
AS LONG WAVE TROUGH IN THE SOUTHEASTERN PACIFIC CROSSES THE ANDES  
LATE ON FRIDAY...IT WILL INTERACT WITH A MOISTENING AIR MASS IN  
NORTHERN ARGENTINA TO SUSTAIN THE DEVELOPMENT OF DEEP CONVECTION.  
EXPECTING DEEP CONVECTION DEVELOPING IN CORDOBA/SANTA FE/ENTRE  
RIOS LATE ON SATURDAY...TO SUSTAIN ACCUMULATIONS OF 20-35MM/DAY.  
 
SANCHEZ...SMN (ARGENTINA)  
SALAZAR...SENAMHI (BOLIVIA)  
GALVEZ...WPC (USA)  
 

 
 
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