714  
FXSA20 KWBC 161532  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1131 AM EDT MON OCT 16 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
NOTE: THERE IS A RISK FOR SEVERE CONVECTION IN NORTH-CENTRAL AND  
NORTHEASTERN ARGENTINA ON TUESDAY AND WEDNESDAY. NOTE THAT THE  
RISK FOR HAIL IS HIGH...PARTICULARLY DURING THE DAY ON  
WEDNESDAY...WHEN A RISK FOR LARGE HAIL EXISTS FROM LA PAMPA-BUENOS  
AIRES PROVINCE NORTH ACROSS CORDOBA/SANTA FE.  
 
MODEL DISCUSSION (VALID FROM OCT 16 AT 0000 UTC): GLOBAL MODELS  
AND ENSEMBLE MEMBERS AGREE ON THE FORECAST EVOLUTION THROUGH 96  
HRS. AFTER THIS PERIOD...THE CONFIDENCE DECREASES VERY RAPIDLY TO  
THE SOUTH OF 45S...ESPECIALLY IN THE EASTERN PACIFIC. NOTE THAT  
CONFIDENCE IN MID-SECTIONS OF THE CONTINENT IS HIGH THROUGH  
12-132HRS.  
 
AN ACTIVE WEATHER PATTERN IS UNRAVELING FOR NORTHEASTERN  
ARGENTINA-URUGUAY-SOUTHERN BRASIL AND PARAGUAY. SEVERAL SHORT WAVE  
TROUGHS ARE TO CROSS THE ANDES AND INTERACT WITH A MOIST AND  
UNSTABLE AIR MASS BREWING IN THE REGION. THROUGH EARLY TUESDAY...A  
SHORT WAVE TROUGH CROSSING THE NORTH-CENTRAL ANDES OF  
ARGENTINA-CHILE WILL LEAD TO LIGHT SNOWFALL IN THE ANDES BETWEEN  
SOUTHERN ANTOFAGASTA AND ATACAMA. THIS TROUGH WILL INTERACT WITH A  
WARM FRONT IN MID-SECTIONS OF THE CONTINENT AND A LOW-LEVEL JET  
FROM THE NORTH TO TRIGGER LATE EVENING CONVECTION ACROSS ENTRE  
RIOS INTO URUGUAY...WITH MAXIMUM ACCUMULATIONS OF 20-35MM/DAY.  
DURING TUESDAY-WEDNESDAY...EXPECTING SEVERE CONVECTION TO DEVELOP  
IN ENTRE RIOS-CORRIENTES INTO URUGUAY AND SOUTHERN RIO GRANDE DO  
SUL...TO PRODUCE MAXIMUM ACCUMULATIONS OF 40-80MM/DAY.  
ALSO...STRONG CONVECTION IS TO DEVELOP IN LA PAMPA/SOUTHERN BUENOS  
AIRES PROVINCE...TO PRODUCE MAXIMA OF 15-25MM. BY  
WEDNESDAY-THURSDAY...A CONTINUED RISK FOR SEVERE CONVECTION IS  
EXPECTED BETWEEN CORRIENTES-ENTRE RIOS-SANTA FE AND  
URUGUAY/SOUTHERN RIO GRANDE DO SUL. NOTE THAT LIFTED INDEX VALUES  
ARE SKIRTING -10 AND THE RISK FOR HAIL IS LARGE. EXPECTING  
ACCUMULATIONS OF 50-100MM/DAY...YET ISOLATED LARGER AMOUNTS ARE  
POSSIBLE IN AREAS UNDER THE INFLUENCE OF STRONGEST THUNDERSTORMS.  
BY THURSDAY...LARGEST ACCUMULATIONS WILL CLUSTER BETWEEN SOUTHERN  
BOLIVIA AND MOST OF PARAGUAY...WHERE SCATTERED CONVECTION WILL  
LEAD TO MAXIMA OF 35-70MM. ENHANCED CONVECTION ALONG THE BOLIVIAN  
YUNGAS AND SOUTHERN PERU WILL LEAD TO MAXIMA OF 25-50MM. IN  
SOUTHERN BRASIL/MISIONES...EXPECTING MAXIMA OF 20-30MM/DAY. DURING  
FRIDAY...A SHORT WAVE TROUGH WILL INTERACT WITH MOISTURE POOL  
SITTING IN PARAGUAY TO LEAD ONCE AGAIN TO STRONG CONVECTION.  
EXPECTING ACCUMULATIONS OF 50-100MM/DAY AND THE RISK FOR MCS  
FORMATION.  
 
ELSEWHERE IN SOUTH AMERICA...FRONTAL CONVECTION IN ESPIRITO SANTO  
WILL LEAD TO ISOLATED MAXIMA OF 15-20MM/DAY ON MONDAY-TUESDAY.  
MAXIMA WILL SHIFT TO SALVADOR DE BAHIA ON TUESDAY-WEDNESDAY WHERE  
EXPECTING AMOUNTS OF 15-25MM/DAY IN A REGION OF ENHANCED TRADE  
WIND CONVERGENCE. AMOUNTS WILL DECREASE AFTER.  
 
ALSO IN TROPICAL SOUTH AMERICA...UNSEASONABLY ACTIVE CONVECTION IS  
EXPECTED IN THE PERUVIAN/BOLIVIAN ANDES EARLY IN THE CYCLE AS  
UPPER TROUGH TO THE SOUTH WEST INTERACTS WITH MOIST AIR MASS IN  
PLACE. THIS WILL LEAD TO MAXIMA OF 15-20MM/DAY ON  
MONDAY-TUESDAY...DECREASING AFTER.  
 
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
GALVEZ...WPC (USA)  

 
 
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