SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
333 PM EDT WED SEP 04 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 04 SEP 2024 AT 1900 UTC:

AN ATMOSPHERIC RIVER IS RAPIDLY MOVING INTO SOUTHERN CHILE AND IS
FORECAST TO ARRIVE LATE ON WEDNESDAY EVENING. THIS SYSTEM IS
ACCOMPANIED BY PRECIPITABLE WATER VALUES IN THE 20-25MM RANGE.
ALTHOUGH THESE VALUES ARE NOT EXTREME AND THE SYSTEM AND
ASSOCIATED FRONTS ARE FORECAST TO MOVE NORTHWARD RAPIDLY...STRONG
LOW-LEVEL WINDS WILL PLAY AN IMPORTANT ROLE IN HIGHLIGHTING
OROGRAPHIC ENHANCEMENT. THROUGH EARLY THURSDAY EXPECT MAXIMA OF
25-50MM FROM MELINKA SOUTH INTO SOUTHERN AYSEN AND MAXIMA OF 15MM
IN LOS LAGOS...INCLUDING MOUNTAIN SNOW. ON THURSDAY...THE
PRECIPITATION WILL FOCUS BETWEEN BIO BIO AND NORTHERN AYSEN WHERE
EXPECT MAXIMA OF 15-20MM AND MOUNTAIN SNOW. AMOUNTS ARE EXPECTED
TO RAPIDLY DECREASE AFTER IN ASSOCIATION WITH THIS ATMOSPHERIC
RIVER.

ANOTHER SYSTEM OF INTEREST IN THE SOUTHERN CONE IS A BROAD UPPER
TROUGH THAT IS AMPLIFYING OVER THE BELLINGSHAUSEN SEA. THIS TROUGH
IS EXPECTED TO GRADUALLY BUILD NORTHWARDS...WHICH WILL YIELD TO A
STRENGTHENING OF THE SOUTHERN POLAR UPPER JET. THIS EVOLUTION WILL
FAVOR THE DEVELOPMENT OF A TRAIN OF SURFACE FRONTS THAT WILL
MEANDER NORTHWARD TO REACH THE SOUTHERN CONE BY LATE THURSDAY.
ONCE AGAIN...EXPECT STRONG WINDS WITH THIS SYSTEM. MODELS ARE
SUGGESTING SPEEDS REACHING VALUES NEAR 70KT AT 850 HPA LATE
THURSDAY EVENING. ENHANCED MOISTURE CONVERGENCE WILL FAVOR ONCE
AGAIN MODERATE PRECIPITATION. FROM LATE THURSDAY TO EARLY
FRIDAY...EXPECT MAXIMA OF 25-50MM DEVELOPING FRMO SOUTHERN AYSEN
INTO THE DARWIN CORDILLERA. THIS PEAKS AT MAXIMA OF 35-70MM ON
FRIDAY INTO EARLY SATURDAY...DUE TO INTERACTIONS WITH THE SOUTHERN
POLAR UPPER JET AND AN ARRIVING UPPER TROUGH. NOTE THAT MOUNTAIN
SNOW IS EXPECTED AS WELL. A COLDER AIR MASS IS EXPECTED LATE IN
THE WEEKEND INTO EARLY NEXT WEEK HIGHLIGHTING SNOWFALL.

A SURFACE FRONT CONTINUES PROPAGATING RAPIDLY ACROSS MID-SECTIONS
OF THE CONTINENT. BY WEDNESDAY EVENING EXPECT IT ACROSS SANTA
CATARINA...PANTANAL...CENTRAL BOLIVIA. BY THURSDAY EVENING EXPECT
A FRONT ACROSS WESTERN RIO DE JANEIRO INTO A FRONTOLIZING BOUNDARY
ACROSS NORTHERN MATO GROSSO DO SUL...RONDONIA...CENTRAL PERU.
INTERACTIONS WITH AN UPPER TROUGH THAT IS CROSSING THE ANDES IS
STIMULATING DEEP CONVECTION FROM SOUTHEAST PARAGUAY INTO SOUTHERN
BRASIL. THROUGH EARLY THURSDAY EXPECT MAXIMA OF 15-25MM FROM
SOUTH-CENTRAL PARAGUAY INTO RIO GRANDE DO SUL. IN EASTERN
PARAGUAY/WESTERN PARANA/SANTA CATARINA EXPECT MAXIMA OF 15-30MM
WITH A SLIGHT RISK OF SEVERITY. ON THURSDAY...EXPECT THE HEAVIEST
PRECIPITATION TO FOCUS IN COLOMBIA/ECUADOR/NORTHERN PERU...WHERE
ENHANCED MOISTURE CONVERGENCE WILL FAVOR MAXIMA OF 15-30MM. IN
WESTERN BRASIL EXPECT MAXIMA OF 15-20MM. IN SOUTHEAST
BRASIL...EXPECT MAXIMA OF 15-20MM.

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