071  
FXSA20 KWBC 131603  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1203 PM EDT FRI OCT 13 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
MODEL DISCUSSION (VALID FROM OCT 13 AT 0000 UTC): MODEL CONFIDENCE  
CONTINUES IS THROUGH 120 HRS. IT STARTS DECREASING IN REGIONS TO  
THE SOUTH OF 50S AFTER.  
 
A TROUGH RAPIDLY-PROPAGATING UPPER TROUGH WILL CROSS THE SOUTHERN  
CONE ON FRIDAY. THIS SYSTEM WILL ARRIVE ACCOMPANIED WITH 40-45KT  
WINDS TO THE SOUTH OF ISLA CHILOE...AND WITH A SUBTROPICAL  
MOISTURE CONNECTION. THE LIMITATION FOR LARGE ACCUMULATIONS WILL  
BE THE FAST PROPAGATION OF THE SYSTEM. STILL...THIS WILL LEAD TO  
MAXIMA OF 15-20MM/DAY BETWEEN ISLA CHILOE AND TAITAO ON  
FRIDAY...AND MAXIMA OF 10-15MM IN REGIONS TO THE SOUTH. BY  
SATURDAY-SUNDAY EXPECTING ALSO MAXIMA OF 15-20MM/DAT IN THE AYSEN  
AND WESTERN MAGALLANES REGIONS. AS A SUBTROPICAL MOISTURE PLUME  
ARRIVES DURING SUNDAY...THIS WILL LEAD TO AN INCREASE IN  
ACCUMULATIONS TO MAXIMA OF 20-30MM. BY SUNDAY-MONDAY EXPECTING A  
DECREASE IN ACCUMULATIONS. A NEW SUBTROPICAL MOISTURE CONNECTION  
IS APPROACHING BIO-BIO...ARAUCANIA AND LOS-LAGOS/LOS RIOS ON  
TUESDAY...STIMULATED BY AN UPPER TROUGH FORECAST TO CROSS THE  
SOUTHERN ANDES LATE ON TUESDAY. THIS WILL LEAD TO AN INCREASE IN  
ACCUMULATIONS TO MAXIMA OF 15-20MM/DAY.  
 
SURFACE FRONT IN MID-SECTIONS OF THE CONTINENTS CONTINUES  
PROPAGATING NORTHWARD WHILE WEAKENING. BY FRIDAY EVENING IT WILL  
EXTEND ACROSS PARANA-BRASIL...WESTERN MATO GROSSO AND NORTHERN  
BOLIVIA. BY SATURDAY EVENING IT WILL EXTEND ACROSS  
PARANA-BRASIL...CENTRAL MATO GROSSO...CENTRAL RONDONIA. BY SUNDAY  
EVENING...THE FRONT WILL EXTEND ACROSS ESPIRITO SANTO...SOUTHERN  
MINAS GERAIS...AND WILL START RETREATING AS A WEAK WARM FRONT  
ACROSS PARAGUAY. INITIALLY...LARGEST ACCUMULATIONS ARE EXPECTED IN  
NORTHERN BOLIVIA AND SOUTHERN PERU AS MOISTURE CONVERGENCE PEAKS  
UNDER THE INFLUENCE OF A SOUTHERLY JET. THIS WILL LEAD TO MAXIMUM  
ACCUMULATIONS OF 40-80MM/DAY. ALSO ON FRIDAY...EXPECTING MAXIMA OF  
15-20MM/DAY IN PARANA AND SANTA CATARINA IN BRASIL. DURING  
SATURDAY...LARGEST ACCUMULATIONS WILL CLUSTER IN ACRE/WESTERN  
AMAZONAS IN BRASIL...INTO CENTRAL AND NORTHERN PERU.  
HERE...ENHANCED LOW-LEVEL MOISTURE CONVERGENCE IN THE LEADING EDGE  
OF THE SOUTHEASTERLY WIND SURGE WILL LEAD TO MAXIMA OF  
40-80MM/DAY. ALSO ON SATURDAY...EXPECTING ACCUMULATIONS OF  
20-30MM/DAY IN THE SERRA DO MAR OF SAO PAULO AND SANTA CATARINA. .  
BY SUNDAY...THE WANING SOUTHEASTERLY SURGE WILL STILL ENHANCE  
PRECIPITATION ACROSS THE NORTHWESTERN AMAZON. EXPECTING MAXIMA OF  
25-50MM/DAY ACROSS NORTHERN PERU/EASTERN ECUADOR INTO SOUTHERN AND  
CENTRAL COLOMBIA. IN BRASIL...FRONTAL CONVECTION WILL LEAD TO  
MAXIMA OF 05-10MM/DAY IN THE RIO DE JANEIRO/ESPIRITO SANTO REGION.  
BY MONDAY-TUESDAY...EXPECTING MAXIMA INCREASING TO 15-20MM/DAY  
ACROSS ESPIRITO SANTO-BRASIL.  
 
ALSO LATE IN THE FORECAST CYCLE...ON TUESDAY-WEDNESDAY...THE  
INTERACTION OF TWO MID-UPPER TROUGHS CROSSING THE ANDES OF CENTRAL  
CHILE AND ARGENTINA...WILL A MOIST AND UNSTABLE AIR MASS BREWING  
IN PORTIONS OF NORTHEASTERN ARGENTINA. THIS WILL POSE THE RISK FOR  
SEVERE CONVECTION IN NORTHEASTERN ARGENTINA/SOUTHERN BRASIL ON  
TUESDAY-WEDNESDAY. NOTE THAT THERE IS A RISK FOR HAIL WITH THIS  
EVENT...ESPECIALLY ACROSS CORRIENTES/NORTHERN ENTRE RIOS INTO  
NORTHERN URUGUAY/SOUTHERN RIO GRANDE DO SUL. THERE IS ALSO A RISK  
FOR HAIL IN LA PAMPA/SOUTHERN BUENOS AIRES PROVINCE ON TUESDAY  
AFTERNOON. IN TERMS OF ACCUMULATIONS...EXPECTING MAXIMA OF  
10-15MM/DAY IN LA PAMPA/SOUTHERN BUENOS AIRES PROVINCE...WHILE IN  
CORRIENTES-URUGUAY-SOUTHERN RIO GRANDE DO SUL EXPECTING MAXIMA OF  
35-70MM/DAY...WITH THE POTENTIAL FOR ISOLATED HIGHER AMOUNTS.  
 
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENMAHI (PERU)  
GALVEZ...WPC (USA)  

 
 
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