SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
249 PM EST TUE NOV 19 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 19 NOV 2024 AT 1850 UTC:

IN THE SOUTHERN STREAM...A BROAD DEEP-LAYER TROUGH CENTERS OVER
THE BELLINGSHAUSEN SEA AND FAR SOUTHEASTERN PACIFIC. MID-UPPER
SHORT WAVE TROUGHS ARE REVOLVING AROUND THE MAIN AXIS. THIS IS
LIMITING THE EASTWARD PROGRESSION OF SURFACE FRONTS ONCE THEY
ARRIVE TO THE SOUTHERN CONE...AND IS ALSO ENHANCING THE MERIDIONAL
COMPONENT OF THE FLOW...WHICH IS LIMITING PRECIPITATION AMOUNTS
WEST OF THE ANDES. THE HIGHEST LIKELIHOOD FOR MODERATE
PRECIPITATION IS EXPECTED ON THURSDAY...WHEN ENHANCED MOISTURE
CONVERGENCE WILL FAVOR 10-15MM/DAY AND MAXIMA OF 20-35MM IN
SOUTHERN AYSEN AND NORTHWEST MAGALLANES IN CHILE.

IN THE NORTHERN STREAM...SHORT WAVE UPPER TROUGHS ARE PROPAGATING
INTO THE CONTINENT. A TROUGH IS FORECAST TO CROSS THE ANDES IF
CENTRAL CHILE AND CENTRAL ARGENTINA ON WEDNESDAY. THE RAPID
PROGRESSION OF THIS SYSTEM AND LIMITED AMOUNTS OF AVAILABLE
MOISTURE WILL LIMIT PRECIPITATION AMOUNTS IN ARGENTINA.
HOWEVER...EXPECT A SLIGHT RISK OF SEVERITY AS CONVECTION DEVELOPS
IN INTERIOR PORTIONS OF CENTRAL ARGENTINA AND NORTHERN PATAGONIA.
ON WEDNESDAY...EXPECT 05-10MM/DAY AND ISOLATED MAXIMA OF 15-30MM
IN MENDOZA/SAN JUAN/SAN LUIS...WHILE IN NORTHERN PATAGONIA EXPECT
MAXIMA OF 15MM. ON THURSDAY...EXPECT MAXIMA OF 10MM AND A MARGINAL
RISK FOR SEVERITY CLUSTERING IN NORTHERN PATAGONIA.

THE BOLIVIAN HIGH CONTINUES WELL ESTABLISHED. THIS IS VENTILATING
CONVECTION IN MOST OF THE AMAZON BASIN BUT ALSO IN CENTRAL
PORTIONS OF THE CONTINENT...AS IT INTERACTS WITH UPPER TROUGHS
MOVING EASTWARD IN THE WESTERLIES. ONE OF THESE TROUGHS IS
CROSSING THE ANDES...AND IS SUSTAINING CYCLOGENESIS IN NORTHEAST
ARGENTINA. IN THE LOW-LEVELS...A FRONT EXTENDS OVER THE SOUTH
ATLANTIC ALONG 28S INTO THE COAST OF RIO GRANDE DO SUL IN BRASIL.
EXPECT CYCLOGENESIS TO DEVELOP ALONG THIS BOUNDARY LATER ON
TUESDAY...WHICH WILL REINFORCE LONG-FETCH MOIST EASTERLY FLOW
ALONG AND TO THE SOUTH OF THE BOUNDARY. THIS WILL FAVOR
15-30MM/DAY AND MAXIMA OF 50-100MM THROUGH EARLY WEDNESDAY...GIVEN
A RISK FOR ECHO TRAINING. IN SOUTHEAST PARAGUAY AND SANTA CATARINA
EXPECT MAXIMA OF 20-45MM. ON WEDNESDAY...AS THE SURFACE LOW EXITS
INTO THE SOUTH ATLANTIC...EXPECT THE COLD FRONT TO ADVANCE
NORTHWARD TO EXTEND INTO SOUTHERN SAO PAULO BY THE EVENING.
PERSISTENT LONG-FETCH ONSHORE FLOW INTO THE MOUNTAINS OF SANTA
CATARINA AND RIO GRANDE DO SUL WILL FAVOR 15-20MM/DAY AND MAXIMA
OF 30-60MM/DAY. ON THURSDAY...EXPECT THE FRONT TO EXTEND ACROSS
SOUTHERN ESPIRITO SANTO...SOUTHERN MINAS GERAIS AND SOUTHERN MATO
GROSSO DO SUL. ONSHORE FLOW WILL FAVOR MAXIMA OF 30-60MM FROM
SANTA CATARINA TO SOUTHERN SAO PAULO. FRONTAL CONVECTION IN
ESPIRITO SANTO/EASTERN RIO DE JANEIRO WILL FAVOR MAXIMA OF
35-70MM. INLAND ACROSS MINAS GERAIS AND MATO GROSSO DO SUL EXPECT
MAXIMA OF 20-45MM.

ANOTHER REGION OF INTEREST IS BOLIVIA...SOUTHERN PERU AND THE
SOUTHWEST AMAZON IN GENERAL. A MID-LEVEL TROUGH EXTENDING OVER
BOLIVIA AND SOUTHERN PERU IS HIGHLIGHTING CONVECTION. PRECIPITABLE
WATER VALUES IN THE REGION ARE IN THE 50-60MM RANGE AND ARE
EXPECTED TO REMAIN HIGH THROUGH THE FORECAST CYCLE. THIS WILL
CONTINUE TO HIGHLIGHT THE POTENTIAL FOR MODERATE AND LOCALLY HEAVY
PRECIPITATION THROUGH THE FORECAST CYCLE. THROUGH EARLY
WEDNESDAY...EXPECT MAXIMA OF 25-50MM IN CENTRAL PERU...AND MAXIMA
OF 20-45MM IN MOST OF LOWER BOLIVIA. IN THE PANTANAL AND NORTHERN
AND EASTERN PARAGUAY EXPECT MAXIMA OF 20-35MM. ON WEDNESDAY
THROUGH EARLY THURSDAY...EXPECT MAXIMA OF 25-50MM IN THE AMAZON OF
CENTRAL AND SOUTHERN PERU...WHILE IN CENTRAL BOLIVIA...NORTHERN
AND EASTERN PARAGUAY/MATO GROSSO DO SUL EXPECT MAXIMA OF 20-35MM.
ON THURSDAY...AN INCREASE IN LOW-LEVEL SOUTHERLY FLOW ACROSS THE
CHACO WILL HIGHLIGHT LOW-LEVEL MOISTURE CONVERGENCE IN BOLIVIA AND
SOUTHERN MATO GROSSO...WHERE EXPECT MAXIMA OF 35-70MM.

NOTE THAT AS A TROPOSPHERIC KELVIN WAVE APPROACHES THE REGION ON
THURSDAY AND INTO THE WEEKEND...ACCUMULATIONS ARE LIKELY TO
INCREASE IN PORTIONS OF THE NORTHWEST AMAZON BASIN. THIS WILL
FAVOR MAXIMA OF 20-40MM IN NORTHWEST BRASIL...NORTHERN PERU AND
SOUTHERN COLOMBIA/ECUADOR BY THURSDAY.

GALVEZ...(WPC)
LOPEZ...(DMH-PARAGUAY)