SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT FRI AUG 23 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 23 AUG 2024 AT 18:55 UTC:

A LARGE UPPER TROUGH CENTERS ON A LOW OVER NORTHEAST PATAGONIA ON
FRIDAY MORNING...AND HAS A SLOW PROGRESSION AS IT MOVES INTO THE
ATLANTIC. THE TROUGH COVERS MOST OF SOUTHERN SOUTH AMERICA AND
EXTENDS IT AXIS NORTH INTO CENTRAL BOLIVIA. THIS TROUGH ASSOCIATES
WITH A BUILDING POLAR HIGH IN CENTRAL ARGENTINA...AND A RELATED
SURFACE FRONT. BY FRIDAY EVENING EXPECT THE FRONT ALONG SAO
PAULO...CENTRAL MATO GROSSO...NORTHERN BOLIVIA...SOUTHERN PERU. BY
SATURDAY EVENING IT IS FORECAST ALONG RIO DE JANEIRO...CENTRAL
MATO GROSSO...ACRE...CENTRAL PERU. BY SUNDAY EVENING EXPECT IT
ACROSS SOUTHERN ESPIRITO SANTO...CENTRAL MATO
GROSSO...RONDONIA...CENTRAL PERU. BY SUNDAY EVENING...EXPECT A
RAPID WEAKENING TREND IN AREAS WEST OF 50W. ALSO ON
SUNDAY...EXPECT THE ORGANIZATION OF A SHEAR LINE...WHICH IS
FORECAST TO EXTEND ACROSS GOIAS...CENTRAL AMAZONAS-BRASIL...THE
BRAZIL-COLOMBIA BORDER. MOST PRECIPITATION IS FORECAST TO REMAIN
IN THE POST-FRONTAL REGION OF THE FRONT...WHERE MOISTURE
CONVERGENCE ASSOCIATED BY THE LOW-LEVEL JET AND INTERACTION WITH
UPPER TROUGH AND UPPER JET DYNAMICS IS FORECAST TO PEAK. ON
FRIDAY...THIS WILL FAVOR MAXIMA OF 20-35MM FROM SOUTHERN MATO
GROSSO DO SUL INTO COASTAL PARANA WITH A MARGINAL RISK OF
SEVERITY. EXPECT ALSO MAXIMA OF 20-35MM IN COASTAL SANTA CATARINA.
OROGRAPHIC INTERACTIONS WILL FAVOR MAXIMA OF 20-35MM IN CENTRAL
BOLIVIA AND MAXIMA OF 15-20MM IN SOUTHERN PERU. ON
SATURDAY...EXPECT MAXIMA OF 15-30MM IN MATO GROSSO DO SUL AND
COASTAL SAO PAULO. ALONG THE EASTERN SLOPES OF THE ANDES IN
CENTRAL/SOUTHERN PERU AND NORTHERN BOLIVIA...OR SELVA
ALTA...EXPECT SIMILAR AMOUNTS. ON SUNDAY...EXPECT THE LARGEST
RAINFALL ACCUMULATIONS IN SOUTHERN RIO DE JANEIRO/SOUTHEAST SAO
PAULO...WHERE ONSHORE POST-FRONTAL SOUTHWESTERLIES WILL TRIGGER
MAXIMA OF 25-50MM. ANOTHER REGION OF INTEREST IS THE TAIL OF THE
SHEAR LINE...WHERE SHEAR LINE CONVERGENCE WILL INTERACT WITH A
PRECIPITABLE WATER POOL OF NEARLY 50MM...AND TRIGGER MAXIMA OF
20-40MM IN FAR NORTHWEST BRASIL INTO SOUTHEAST COLOMBIA. CONTINUED
MOISTURE CONVERGENCE IN NORTHERN AND CENTRAL PERU WILL FAVOR
MAXIMA OF 20-35MM.

ANOTHER SYSTEM OF INTEREST IS AN ATMOSPHERIC RIVER THAT IS
FORECAST TO ENTER IN SOUTHERN CHILE EARLY ON SUNDAY. HOWEVER...THE
SYSTEM AND ITS ASSOCIATED FRONT WILL NOT EXHIBIT A ZONAL
ORIENTATION...WHICH WILL LIMIT POTENTIAL ACCUMULATION. THIS WILL
YIELD IN MAXIMA GENERALLY UNDER 15MM/DAY ON SUNDAY...EXTENDING
FROM BIO BIO SOUTH INTO NORTHERN MAGALLANES. THIS INCLUDES
MOUNTAIN SNOWFALL.

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