546
FXSA20 KWBC 311739
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1239 PM EST TUE DEC 31 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 31 DEC 2024 AT 1740 UTC:
NOTE: THE NEXT UPDATE TO THE SOUTH AMERICAN FORECAST BULLETIN WILL
BE ON 02 JANUARY 2025. WE APOLOGIZE FOR THE INCONVENIENCE.
ON TUESDAY...THE SOUTHERN CONE OF THE CONTINENT IS SEEING THE
PRESENCE OF A CUTOFF LOW PRESSURE SYSTEM IN THE UPPER
LEVELS...EXPECTED TO BE CENTERED JUST OFFSHORE TO THE EAST OF
CHUBUT AND SANTA CRUZ PROVINCES OF ARGENTINA BY TUESDAY NIGHT.
THESE UPPER LEVEL FEATURE IS EMBEDDED IN A PROGRESSIVE PATTERN OF
TROUGHS PASSING THROUGH THE SOUTHERN PORTION OF THE CONTINENT OVER
THE NEXT SEVERAL DAYS. IN THE LOWER LEVELS A SURFACE LOW PRESSURE
SYSTEM ASSOCIATED WITH THE AFOREMENTIONED UPPER TROUGH WILL FAVOR
MOIST ONSHORE FLOW INTO THE PATAGONIA REGION OF ARGENTINA...WITH
PRECIPITABLE WATER LEVELS REACHING 25MM. AS THIS MOISTURE ENTERS
THE PATAGONIA...MOISTURE CONVERGENCE ALONG THE HIGHER ELEVATIONS
WILL FAVOR MODERATE TO HEAVY PRECIPITATION MAXIMA OF 20-40MM IN
THE REGIONS OF CENTRAL SANTA CRUZ-ARGENTINA WITH A RISK OF
THUNDERSTORMS. LOCALLY HIGHER AMOUNTS OF PRECIPITATION ARE
POSSIBLE. AS THIS SYSTEM QUICKLY PUSHES EAST AND NORTHWARD...THE
ASSOCIATED FRONTAL BOUNDARY IS EXPECTED TO ENTER THE BUENOS AIRES
REGION AND CENTRAL ARGENTINA BY WEDNESDAY EVENING. THE MID TO
UPPER TROUGH WILL HAVE EMBEDDED SHORTWAVE TROUGHS THAT COULD BEGIN
TO TILT NEGATIVELY AS THEY CROSS OVER URUGUAY AND SOUTH
BRASIL...ENHANCING THE POTENTIAL FOR SEVERE WEATHER IN THE REGION.
HOWEVER...PRECIPITATION TOTALS ARE EXPECTED TO REMAIN BELOW 25MM.
ON THURSDAY...THE FRONTAL BOUNDARY CONTINUES INTO URUGUAY AND
NORTH ARGENTINA. AS THE PRESSURES IN THE LOWER LEVELS ARE
DECREASING WITH THE PASSING OF THE UPPER TROUGH...MOISTURE IS
BEING TRANSPORTED FROM THE NORTHERN PORTION OF THE CONTINENT INTO
THE CHACO REGION OF ARGENTINA...PARAGUAY AND INTO SOUTH BOLIVIA.
THIS MOISTURE WILL CONVERGE ALONG THE ANDES MOUNTAIN AND FAVOR
HEAVY PRECIPITATION OF 20-45MM. IN SOUTHERN CHILE...AND
ATMOSPHERIC RIVER WITH HIGHER THAN NORMAL AMOUNTS OF PRECIPITABLE
WATER...EXCEEDING THE 30-35MM RANGE AS IT ENTERS SOUTH CHILE BY
WEDNESDAY AFTERNOON. DUE TO THE FAST PROGRESSION OF THE
SYSTEM...ACCUMULATION AMOUNTS ARE NOT EXPECTED TO BE ELEVATED. BY
THURSDAY MORNING...THE FRONTAL SYSTEM ASSOCIATED WITH THE
AFOREMENTIONED ATMOSPHERIC RIVER HAS DISSIPATED AS IT MAKES
CONTACT WITH THE ANDES MOUNTAIN RANGE AND A DECREASE IN
PRECIPITATION IS EXPECTED IN THE AUSTRAL REGION OF CHILE ON
THURSDAY.
TO THE NORTH...THE BOLIVIAN HIGH IS MEANDERING OVER MOST OF THE
NORTHERN PORTION OF THE CONTINENT...AND CENTERED IN BOLIVIA...AND
EXTENDING SOUTH INTO NORTH ARGENTINA ON TUESDAY AFTERNOON. AN
UPPER LEVEL TROUGH EXTENDS INTO SOUTH BRASIL...WHERE THE BASE IS
EXPECTED IN MINAS GERAIS AND ESPIRITO SANTO BY TUESDAY EVENING.
THE EASTERN REGION OF BRASIL CAN EXPECT DIFFLUENCE IN ASSOCIATION
WITH THE INTERACTION BETWEEN THE BOLIVIAN HIGH AND THE UPPER LEVEL
TROUGH AND HEAVY THUNDERSTORMS COULD BE EXPECTED ON TUESDAY INTO
WEDNESDAY MORNING. TO THE NORTH AND WEST...ANOTHER UPPER LEVEL
TROUGH EXTENDS INTO NORTH PERU FROM THE EAST PACIFIC OCEAN...WHERE
THE SUBEQUATORIAL JET IS INTERACTING WITH THE BOLIVIAN HIGH OVER
ECUADOR...COLOMBIA...NORTH PERU...AND WEST BRASIL. THESE
INTERACTIONS WILL PROVIDE A DIFFLUENT PATTERN OVER THE NEXT
SEVERAL DAYS AS THE BOLIVIAN HIGH IS EXPECTED TO INTENSIFY OVER
THE FORECAST PERIOD.
IN TERMS OF PRECIPITATION...IN THE NORTHERN PORTION OF THE
CONTINENT EXPECT MAXIMA OF 30-60MM IN AMAZONAS-BRASIL...WHILE
NORTH PERU CAN EXPECT MAXIMA OF 20-35MM. ON WEDNESDAY...THE REGION
CAN EXPECT MAXIMA OF 20-35MM IN AMAZONAS-BRASIL INTO CENTRAL
PORTIONS OF THE BRASILIAN COUNTRY. ON THURSDAY...MAXIMA OF 20-45MM
ARE EXPECTED IN EAST ECUADOR...NORTH PERU...AND MAXIMA OF 20-35MM
IN NORTHWEST BRASIL. IN EASTERN BRASIL...THE EFFECTS OF THE UPPER
TROUGH WILL FAVOR DESTABILIZATION AND DEEP CONVECTION IN MINAS
GERAIS...RIO DE JANEIRO...AND ESPIRITO SANTO. OVER THE NEXT THREE
DAYS...THE REGION CAN EXPECT GENERALIZED MAXIMA OF 20-50MM PER DAY
WITH A POSSIBILITY OF HIGHER LOCALIZED TOTALS.
CASTELLANOS...(WPC)
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