308
FXSA20 KWBC 171951
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 PM EST FRI JAN 17 2025
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 17 JAN 2025 AT 2000 UTC:
NOTE: THE SOUTH AMERICAN DESK BULLETIN AND CHARTS WILL BE PAUSED
ON 20 JANUARY 2025. THE NEXT UPDATE TO THE SOUTH AMERICAN DESK
PRODUCTS WILL BE ON 21 JANUARY 2025. WE APOLOGIZE FOR THE
INCONVENIENCE.
ON FRIDAY...THE SOUTHERN PORTION OF THE CONTINENT IS SEEING AN
UPPER LEVEL TROUGH ENTER THE REGION...AND INTERACT WITH THE
BOLIVIAN HIGH TO THE NORTH. THE INTERACTION BETWEEN THE TWO IS
FAVORING SHORTWAVE TROUGHS OVER CENTRAL ARGENTINA...WHICH WILL
ASSIST IN THE DEVELOPMENT OF SEVERE STORMS ON FRIDAY INTO
SATURDAY. THIS UPPER TROUGH IS ADVANCING THE FRONTOGENESIS OVER
CENTRAL ARGENTINA...AND WILL BE SUPPORTED BY THE UPPER LEVEL
TROUGH THAT EXTENDS OVER SOUTH CHILE INTO ARGENTINA. THE CENTRAL
REGION OF ARGENTINA CAN EXPECT MAXIMA OF 20-35MM WITH A MODERATE
RISK OF SEVERE WEATHER. ON SATURDAY...THE UPPER LEVEL TROUGH
PROPAGATES TO THE NORTH AND EAST...WHERE THE BASE OF THE TROUGH IS
DEVELOPING INTO A SHORTWAVE TROUGH OVER NORTHERN CHILE AND
NORTHWEST ARGENTINA. IN THE LOWER LEVELS...THE FRONTAL BOUNDARY
STRENGTHENS AND IS EXPECTED FROM SOUTH SAN
JUAN-ARGENTINA...THROUGH ENTRE RIOS-ARGENTINA...AND SOUTH URUGUAY
WHERE IT THEN EXITS INTO THE SOUTH ATLANTIC. AN OUTFLOW BOUNDARY
IS EXPECTED AHEAD OF THE FRONT OVER NORTH URUGUAY...AND NORTHERN
PORTIONS OF ARGENTINA BY SATURDAY EVENING. A MODERATE RISK OF
SEVERE WEATHER IS EXPECTED FROM NORTH ARGENTINA TO BUENOS AIRES
REGION...AND EXTREME WEST URUGUAY WITH MAXIMA OF 20-45MM. ON
SUNDAY...THE BASE OF THE SHORT WAVE TROUGH IS EXPECTED IN NORTH
ARGENTINA/URUGUAY AND INTO SOUTH BRASIL BY THE EVENING HOURS. THE
FRONTAL BOUNDARY IS EXPECTED FROM THE WESTERN INTERIOR REGION OF
THE CHACO BETWEEN BOLIVIA AND ARGENTINA...EXTENDING INTO SOUTH
PARAGUAY...AND INTO RIO GRANDE DO SUL. IN URUGUAY...A TROUGH IS
DEVELOPING JUST WEST OF THE TROUGH WITH A POTENTIAL FOR
CYCLOGENESIS ON MONDAY. INCREASED LEVELS OF PRECIPITABLE WATER ARE
EXPECTED TO BE ADVECTED ONSHORE INTO URUGUAY AND ENTRE
RIOS-ARGENTINA...WITH VENTILATION FROM THE DIVERGENT SIDE OF THE
UPPER SHORTWAVE TROUGH. THIS WILL FAVOR MAXIMA OF 40-80MM WITH A
SLIGHT RISK OF SEVERE WEATHER.
ON FRIDAY AFTERNOON..THE BOLIVIAN HIGH IS PRESENTING AS AN
ELONGATED HIGH PRESSURE SYSTEM...EXTENDING FROM THE EASTERN
PACIFIC OCEAN TO THE WEST OF PERU...INTO SOUTH PERU AND
BOLIVIA...AND A SECONDARY CELL LOCATED OVER NORTH PARAGUAY AND
SOUTH BRASIL. THIS IS DUE TO THE INTERACTION OF A RETROGRADING
UPPER LEVEL TROUGH ENTERING EAST BRASIL...BRINGING WITH IT DRIER
CONDITIONS INTO THE REGION OF EAST BRASIL. AS THIS INTERACTION IS
TAKING PLACE OVER PORTIONS OF NORTH AND CENTRAL BRASIL...INCREASED
DIVERGENCE IS EXPECTED ON FRIDAY...FAVORING DEEP CONVECTION IN
CENTRAL BRASIL. IN THE LOWER LEVELS...DRY AIR IS BEING ADVECTED IN
THE TRADE WINDS FROM THE EAST INTO EAST BRASIL...WHERE
PRECIPITATION IS EXPECTED TO REMAIN MINIMAL ON FRIDAY.
HOWEVER...THE MOISTURE OVER THE AMAZON RIVER BASIN WILL CONTINUE
TO CONVERGE IN NORTH AND CENTRAL BRASIL...WHERE IT WILL CONTINUE
PROPAGATING WEST INTO BOLIVIA BY SATURDAY MORNING. ON
FRIDAY...MAXIMA OF 40-80MM ARE EXPECTED IN AMAPA-BRASIL AS
MOISTURE IS CONVERGING ALONG THE COAST AS A MOIST TROUGH ENTERS
THE REGION. VENTILATION FROM THE UPPER LEVEL DIVERGENCE WILL FAVOR
HEAVY PRECIPITATION. NORTH PARA-BRASIL CAN EXPECT MAXIMA OF
30-60MM WITH THE PRESENCE OF THE ITCZ/NET INTERACTING WITH THE
VENTILATION FROM THE UPPER LEVELS. IN THE SOUTH...FROM NORTH MATO
GROSSO DO SUL AND MATO GROSSO INTO EAST BOLIVIA...EXPECT MAXIMA OF
35-70MM. ON SATURDAY...THE UPPER LEVEL TROUGH IN EAST BRASIL
CONTINUES TO PROPAGATE WEST EXTENDING FROM THE EASTERN COAST OF
BRASIL TO EAST MATO GROSSO AND GOIAS BY SATURDAY EVENING. THE
BOLIVIAN HIGH IS ALSO MEANDERING TO THE WEST AND THE MAIN CELL IS
EXTENDING OVER THE EAST PACIFIC AND EXTENDING OVER MOST OF
PERU...BOLIVIA...AND WEST BRASIL. A WEAKER ELONGATED CELL OF THE
BOLIVIAN HIGH EXTENDS INTO SOUTH BRASIL. IN THE LOWER
LEVELS...AREAS OF MOISTURE CONVERGENCE ARE EXPECTED OVER THE
AMAZON RIVER BASIN IN PARA AND MATO GROSSO...WHEREAS TO THE
EAST...THE PRESENCE OF THE UPPER LEVEL TROUGH AND ADVECTED DRY AIR
IS DRYING MOST OF EASTERN BRASIL ON SATURDAY. IN TERMS OF
PRECIPITATION...EXPECT MAXIMA OF 35-70MM IN NORTH
PARA-BRASIL...AND MAXIMA OF 30-60MM IN MATO GROSSO. PORTIONS OF
AMAPA...AND SOUTH PARA CAN EXPECT MAXIMA OF 20-45MM. A LOW LEVEL
TROUGH IN SAO PAULO IS FAVORING CONVECTION OVER THE REGION AND
WILL FAVOR SIMILAR AMOUNTS. ON SUNDAY...THE AFOREMENTIONED FRONTAL
BOUNDARY ORIGINATING FROM CENTRAL ARGENTINA IS EXPECTED TO
INTERACT WITH THE LARGE AMOUNT OF MOISTURE FROM THE NORTH IN
REGIONS OF BOLIVIA AND PARAGUAY. EXPECT THE INFLUENCE OF THE UPPER
DIVERGENCE ASSOCIATED WITH THE PERIPHERY OF THE BOLIVIAN HIGH TO
FAVOR DEEP CONVECTION IN THE REGION ON SUNDAY. AS THE FRONTAL
BOUNDARY ENTERS THE REGION...EXPECT MAXIMA OF 50-100MM FROM
TARIJA-BOLIVIA TO SOUTH SANTA CRUZ-BOLIVIA. MAXIMA OF 30-60MM ARE
EXPECTED FROM NORTH PARAGUAY TO SOUTHEAST SANTA CRUZ-BOLIVIA. RIO
GRANDE DO SUL-BRASIL CAN EXPECT MAXIMA OF 25-50MM WITH A MODERATE
RISK OF SEVERE WEATHER. CENTRAL PORTIONS OF BOLIVIA CAN EXPECT
MAXIMA OF 20-45MM ON SUNDAY. AS THIS SYSTEM CONTINUES TO PROPAGATE
NORTHWARD...REGIONS OF HEAVY PRECIPITATION ARE EXPECTED IN CENTRAL
PORTIONS OF BOLIVIA ON MONDAY...AS AREAS OF VENTILATION FROM THE
INTERACTION BETWEEN AN UPPER LEVEL TROUGH OVER CENTRAL BRASIL AND
THE BOLIVIAN HIGH TO THE WEST.
CASTELLANOS...(WPC)
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