SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
352 PM EDT THU SEP 12 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 12 SEP 2024 AT 1945 UTC:

ON THURSDAY...THE SEVERE CONDITIONS OVER PORTIONS OF
PARAGUAY...NORTH AND EAST ARGENTINA...SOUTHERN BRASIL...AND
URUGUAY ARE EXPECTED TO CONTINUE. THE UPPER LEVEL TROUGH EXTENDS
INTO THE CENTRAL BOLIVIA...AND CENTRAL BRASIL...WITH A SHORTWAVE
TROUGH OVER AMAZONAS-BRASIL. THE POTENT BLOCKING PATTERN OVER
WESTERN SOUTH AMERICA....ALSO IS PRESENT OVER THE NORTHEASTERN
SOUTH AMERICA. THIS PATTERN WILL FAVOR THE DEVELOPMENT OF SHORT
WAVE TROUGHS EMBEDDED ALONG THE WIDE TROUGH OVER CENTRAL BOLIVIA
AND CENTRAL BRASIL...AND EXTEND INTO PARAGUAY...ARGENTINA..AND
SOUTH BRASIL/URUGUAY. SOME OF THESE SHORT WAVE TROUGHS COULD ALSO
BE IN A NEGATIVELY TILTEDÂPOSITION...ENHANCING THE POTENTIAL FOR
SEVERE WEATHER. IN ADDITION...THE INTERACTIONS BETWEEN THESE MID
TO UPPER LEVEL SYSTEMS WILL FAVOR STRONG DIFFLUENCE ON
THURSDAY....AND IT IS EXPECTED TO INCREASE OVER THE FORECAST
PERIOD AS THE MID TO UPPER TROUGH PROPAGATES TO THE NORTH AND
EAST. THE INCREASE OF AVAILABLE MOISTURE OVER THE NEXT THREE DAYS
WILL FAVOR FOR INCREASED AMOUNTS OF PRECIPITATION IN THE REGION.
IN THE LOWER LEVELS...A FRONTAL BOUNDARY EXTENDS FROM PORTIONS OF
SOUTH-CENTRAL BOLIVIA...THE BORDER REGION OF PARAGUAY AND
BRASIL...INTO PARANA AND SANTA CATARINA IN BRASIL...BECOMING THE
TRIGGER FOR CONVECTION IN THE REGION. IN TERMS OF
PRECIPITATION...EXPECT MAXIMA OF 35-70MM IN SOUTHERN
PARAGUAY...AND MISIONES/CORRIENTES IN ARGENTINA. MAXIMA OF 20-45MM
ARE EXPECTED IN SANTA CATARINA AND RIO GRANDE DO SUL. THE
AFOREMENTIONED REGIONS CAN EXPECT A MODERATE RISK OF SEVERE
WEATHER. CENTRAL PORTIONS OF BOLIVIA CAN EXPECT MAXIMA OF 15-20MM
WITH A SLIGHT CHANCE OF SEVERE WEATHER. BY FRIDAY....THE FRONT IS
EXPECTED TO STATIONARY OVER EAST-CENTRAL BOLIVIA...INTO
PARAGUAY...AND INTO PARANA-BRASIL. FROM NORTHERN PARAGUAY...TO
WEST PARANA...EXPECT MAXIMA OF 30-60MM WITH A MODERATE RISK OF
SEVERE WEATHER. TO THE NORTH...IN SOUTHERN BOLIVIA...INTO NORTH
PARAGUAY...EXPECT MAXIMA OF 20-40MM. TO THE SOUTH...IN SANTA
CATARINA AND EAST RIO GRANDE DO SUL...EXPECT MAXIMA OF 20-45MM
WITH A SLIGHT RISK OF SEVERE WEATHER. ELSEWHERE IN SOUTH
BRASIL...AND NORTH BOLIVIA...EXPECT MAXIMA BELOW 25MM. BY
SATURDAY...THE FRONTAL BOUNDARY IS EXPECTED TO GET ASSISTANCE FROM
THE PROGRESSIVE UPPER LEVEL TROUGH THAT ENHANCES ITS EAST AND
NORTHWARD MOVEMENT FROM SATURDAY EVENING ONWARD. AVAILABLE
MOISTURE CONTINUES TO REMAIN HIGH AND FAVOR MAXIMA OF 35-70MM IN
EAST PARAGUAY...AND INTO MATO GROSSO DO SUL AND NORTH PARANA. A
MODERATE RISK OF SEVERE WEATHER IS EXPECTED. MAXIMA OF 20-45MM IS
EXPECTED IN SAO PAULO WITH A MARGINAL RISK OF SEVERE WEATHER.
NORTHEAST BOLIVIA CAN EXPECT MAXIMA OF 20-40MM.

IN THE SOUTHERN CONE OF THE CONTINENT...SOUTHERN CHILE COULD
EXPECT THE ADVECTION OF COLDER AIR AND SOME MOISTURE WITH THE
PRESENCE OF FRONTAL BOUNDARIES MOVING INTO THE AREA OVER THE NEXT
FEW DAYS. ON THURSDAY...A FRONTAL BOUNDARY EXTENDS INTO NORTH
AYSEN AND IT IS QUICKLY FOLLOWED BY A SECONDARY COLD FRONT COMING
FROM THE SOUTH THAT WILL BRING COLDER AIR OVER THE WEEKEND. BY
FRIDAY...THE FRONTAL BOUNDARY HAS DISSIPATED OVER THE
CONTINENT...BUT A COLD PORTION OF THE FRONT EXTENDS INTO THE
SOUTHEASTERN COAST OF BUENOS AIRES. ON SATURDAY AN ATMOSPHERIC
RIVERÂADVANCES OVER THE SOUTHEASTERN PACIFICÂ AND APPROACHES THE
SOUTHERN REGION OF CHILE. THERE WILL BE A SLIGHT INCREASE OF
AVAILABLE MOISTURE...AND THUS A GENERAL INCREASE OF PRECIPITATION
IN THE REGION. ON THURSDAY AND FRIDAY...EXPECT MAXIMA TO REMAIN
BELOW 20MM IN ZONA SUR AND ZONA AUSTRAL. THE SNOWFALL MAX OF
05-10CM ARE EXPECTED IN SOUTHERN MAGALLANES ON THURSDAY. ON
SATURDAY...EXPECT MAXIMA OF 15-30MM IN SOUTH AYSEN AND NORTH
MAGALLANES...WHILE MAXIMA WILL REMAIN BELOW 15MM IN NORTH AYSEN
AND SOUTH MAGALLANES.

ACOSTA...(WPC)