SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1024 AM EDT THU JUL 08 2021

GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/

FORECAST DISCUSSION FROM JUL 08/15UTC:  A BROAD MID/UPPER LEVEL
TROUGH IS TO DOMINATE THE FLOW OVER THE SOUTHERN CONE DURING THE
NEXT TWO DAYS...THEN QUICKLY PULLS TO THE EAST-SOUTHEAST ON
SATURDAY AS A DEEPENING SOUTHERN STREAM TROUGH AMPLIFIES ACROSS
THE SOUTHEAST PACIFIC/BELLINGSHAUSEN SEA TO TIERRA DEL FUEGO. THE
LATTER BOTTOMS OUT OVER SOUTHERN PATAGONIA EARLY ON SUNDAY
MORNING...WITH AXIS TO THEN GRADUALLY WEAKEN WHILE SLOWLY PULLING
TO THE EAST-SOUTHEAST EARLY NEXT WEEK. AT LOW LEVELS...THIS
SUSTAINS A BROAD TROUGH OVER THE SOUTHEAST PACIFIC/SOUTHERN
CONE...WITH POLAR FRONTS REVOLVING AROUND THIS TROUGH TO INITIALLY
CONFINE TO SOUTHERN CHILE AND PATAGONIA IN ARGENTINA. ON FRIDAY A
FRONT BREAKS FREE AND SURGES ACROSS LA PAMPA TO CENTRAL
ARGENTINA...WITH THE FRONT STALLING OVER SOUTHERN BRASIL-NORTHERN
ARGENTINA LATER ON SATURDAY. DURING THE WEEKEND A BROAD/LOW
AMPLITUDE TROUGH IS TO THEN ENTER THE DRAKE PASSAGE/SOUTHERN
CHILE-PATAGONIA...TO PULL AWAY LATER ON MONDAY AFTERNOON. MOST
ACTIVE CONVECTION WITH THESE SYSTEMS IS EXPECTED ACROSS SOUTHERN
CHILE...WITH ORGANIZED CONVECTION EARLY IN THE CYCLE TO SUSTAIN
MODERATE TO HEAVY RAINFALL AMOUNTS. EARLY ON THE ACTIVITY WILL
SPLIT IN TWO AREAS...WITH ONE BETWEEN CONCEPCION AND PUERTO MONTT
TO SUSTAIN MAXIMA OF 20-45MM IN POTENTIALLY DEEP CONVECTION. THIS
RAPIDLY EBBS ON FRIDAY. SOUTH OF PUERTO MONTT THIS WILL SUSTAIN
RAINFALL MAXIMA OF 20-35MM THROUGH FRIDAY MORNING. THROUGH THE
DAY...IN A COLD ADVECTIVE PATTERN...EXPECTING A PHASE
CHANGE...WITH SOLID PRECIPITATION (SNOW) TO CLUSTER ACROSS THE
SOUTHERN ANDES TO TIERRA DEL FUEGO. IN THIS AREA EXPECTING
ACCUMULATION OF 10-15CM/DAY TO PERSIST THROUGH MONDAY. 

DURING THE MEDIUM RANGE PERIOD THE SYSTEM OF CONCERN IS A
MID/UPPER LEVEL TROUGH ON THE NORTHERN STREAM THAT SLOWLY PULLS
TOWARDS THE CENTRAL/NORTHERN REGIONS OF CHILE EARLY ON MONDAY
MORNING. THE SHORT WAVE TROUGH IS TO THEN SLOWLY SPILL ACROSS THE
CENTRAL ANDES INTO ARGENTINA EARLY NEXT WEEK. AS IT ENTERS THE
CONTINENT THIS WILL TRIGGER SCATTERED SNOW SHOWERS ALONG THE
CENTRAL AND NORTHERN ANDES OF CHILE. OTHER ACTIVITY IS EXPECTED TO
THE EAST OVER CENTRAL ARGENTINA AS THE SHORT WAVE TROUGH SHEARS
SHORT WAVE ENERGY ACROSS THE ANDES. THIS WILL INTERACT WITH A
MEANDERING FRONT TO SUSTAIN A FRONTAL WAVE. THIS STRENGTHENS THE
FRONTAL BOUNDARY WHILE TRIGGERING HEAVY RAINFALL AMOUNTS. MOST
INTENSE IS EXPECTED ON MONDAY TO TUESDAY...WITH ACCUMULATION OF
35-70MM.

UPPER FLOW PATTERN OVER NORTHERN SOUTH AMERICA SPLITS BETWEEN A
SHORT WAVE TROUGH OVER WESTERN BRASIL AND A SHORT WAVE RIDGE TO
THE EAST/NORTHEAST. THROUGH FRIDAY AFTERNOON THE TROUGH IS TO
WEAKEN/FILL AS ANOTHER LIFTS ACROSS PERU/BOLIVIA. THROUGH SATURDAY
THE LATTER IS TO THEN AMPLIFY TO THE NORTH/NORTHWEST ALONG THE LEE
OF THE PERUVIAN ANDES TO COLOMBIA. THE TROUGH IS TO THEN SLOWLY
MOVE EAST ACROSS BRASIL AS AN UPPER LEVEL RIDGE BUILDS FROM THE
WEST. MOST ACTIVE CONVECTION WITH THESE PERTURBATIONS IS TO
CLUSTER ACROSS EASTERN ECUADOR TO CENTRAL COLOMBIA...WITH MODERATE
RAINFALL AMOUNTS OF 20-30MM/DAY...WHILE TO THE EAST ACTIVITY
ACROSS NORTHERN PERU-AMAZONAS IN BRASIL WILL SUSTAIN RAINFALL
AMOUNTS OF 15-20MM/DAY. THROUGH EARLY NEXT WEEK THE CONVECTION IS
TO SPREAD EASTWARD ACROSS EQUATORIAL SOUTH AMERICA...EXPANDING
ACROSS PARA TO AMAPA/AMAZON RIVER DELTA. THIS IS CONSIDERABLY
WETTER THAN NORMAL FOR THIS TIME OF THE YEAR.

DAVISON...WPC (USA)