SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
330 PM EDT TUE SEP 03 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 03 SEP 2024 AT 1930 UTC:

A TIGHT BELT OF WESTERLIES IN THE SOUTHERN CONE IS FORECAST TO
PERSIST THROUGH THE LATE WORK WEEK TO FAVOR SEVERAL DAYS WITH
SCATTERED PRECIPITATION AND IN AREAS SOUTH OF 48S. THE COLDEST
CONDITIONS ARE EXPECTED ON TUESDAY...WHEN 1000-500 HPA THICKNESS
DROPPING TO 5280 GPM DURING THE DAY WILL LIKELY ENHANCE PERIODS
WITH SNOW VERSUS THOSE WITH RAIN. NEVERTHELESS...EXPECT AN
INCREASE IN THICKNESS/WARMING EARLY ON WEDNESDAY...WHICH WILL
LIKELY STIMULATE A MIX OF RAIN AND SNOW DURING THE REST OF THE
FORECAST CYCLE. ON TUESDAY EXPECT MAXIMA OF 15-30MM ACCOMPANIED BY
MOUNTAIN SNOW. ON WEDNESDAY EXPECT SIMILAR AMOUNTS IN THE DARWIN
CORDILLERA AND WINDS APPROACHING 50KT IN THE BOUNDARY LAYER IN
NORTHERN PORTIONS OF THE DRAKE PASSAGE. ON THURSDAY EXPECT A MOIST
AIRMASS TO MOVE IN FROM THE WEST TO FAVOR AN INCREASE IN
PRECIPITATION TOTALS TO MAXIMA OF 20-45MM.

ANOTHER SYSTEM OF INTEREST IS AN ATMOSPHERIC RIVER AND SET OF
ASSOCIATED FRONTS. ON TUESDAY AFTERNOON...THE WARM FRONT...TRIPLE
POINT AND FRONTAL EDGE OF THE MOIST PLUME ARE APPROACHING 38S
100W. THIS SYSTEM IS FORECAST TO ENTER SOUTHERN CHILE LATE ON
WEDNESDAY AND PROGRESS NORTHWARD WHILE WEAKENING DURING THURSDAY.
THE RAPID PROGRESSION AND MERIDIONAL WINDS IN THE LOW TROPOSPHERE
WILL LIMIT POTENTIAL ACCUMULATIONS WITH THIS SYSTEM. ON WEDNESDAY
THROUGH EARLY THURSDAY EXPECT MAXIMA OF 25-50MM FROM MELINKA SOUTH
INTO SOUTHERN AYSEN. IN ISLA CHILOE/LOS LAGOS EXPECT MAXIMA OF
15MM. ON THURSDAY EXPECT MAXIMA OF 20-35MM FROM TAITAO INTO
ARAUCANIA. NOTE THAT MOUNTAIN SNOW IS EXPECTED THROUGH THE EVENT.

A BROAD MID-UPPER RIDGE OVER THE EASTERN PACIFIC ASSOCIATES WITH A
POTENT UPPER JET ALONG ITS SOUTHERN PERIPHERY. THIS
JET...CURRENTLY LOCATED OFF THE COAST OF CENTRAL CHILE...WILL
YIELD TO THE AMPLIFICATION OF AN UPPER TROUGH THROUGH WEDNESDAY.
THE AMPLIFICATION OF THE TROUGH AND ITS EXPECTED EAST-NORTHEAST
TRAJECTORY WILL STIMULATE ASCENT FROM NORTHEAST ARGENTINA
INITIALLY INTO SOUTHEAST BRAZIL BY THURSDAY. PRECIPITABLE WATER IS
APPROACHING 40MM IN CORRIENTES/NORTHERN URUGUAY. THIS AND A
WEAKENING SURFACE FRONT WILL TRIGGER NOCTURNAL CONVECTION EARLY ON
WEDNESDAY TO FAVOR MAXIMA OF 15-30MM/DAY AND A MARGINAL RISK OF
SEVERITY. EXPECT THE EVENT TO PEAK ON WEDNESDAY THROUGH EARLY
THURSDAY...WHEN AMOUNTS ARE FORECAST TO REACH 10-15MM/DAY AND
MAXIMA OF 20-40MM FROM SOUTHERN PARAGUAY INTORIO GRANDE DO SUL. IN
EASTERN PARAGUAY/MISIONES-ARGENTINA AND WESTERN PARANA EXPECT
MAXIMA OF15-30MM WITH A SLIGHT RISK FOR SEVERE WEATHER. ON
THURSDAY...EXPECT MAXIMA OF 15-20MM FROM SANTA CATARINA/PARANA
INTO COASTAL SAO PAULO. NOTE A MARGINAL RISK FOR SEVERITY AS WELL.

THE AFOREMENTIONED EVENT IN CENTRAL SOUTH AMERICA WILL ASSOCIATE
WITH A RAPIDLY-PROGRESSING SURFACE FRONT ACROSS CENTRAL PORTIONS
OF THE CONTINENT. BY WEDNESDAY EVENING EXPECT THE FRONT ACROSS
SANTA CATARINA...PANTANAL...CENTRAL BOLIVIA. BY THURSDAY EVENING
EXPECT A FRONTOLIZING BOUNDARY ACROSS RIO DE JANEIRO...CENTRAL
MATO GROSSO...NORTHERN PERU. MOISTURE CONVERGENCE IS EXPECTED TO
PEAK IN THE WESTERN AMAZON BASIN ON THURSDAY...WHEN EXPECT MAXIMA
OF 20-40MM IN NORTHERN PERU/ECUADOR...AND MAXIMA OF 15-30MM IN FAR
WESTERN BRASIL.

GALVEZ...(WPC)
TINOCO...(WPC)