051
FXSA20 KWBC 211941
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
340 PM EDT WED AUG 21 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 21 AUG 2024 AT 19 UTC:
A LARGE AND POTENT UPPER TROUGH IS CROSSING THE ANDES ON
WEDNESDAY. THE TROUGH CENTERS ON A LOW NEAR 41S AND 74W...AND
EXTENDS AN AXIS NORTH INTO NORTHWEST BOLIVIA. THE SYSTEM IS ALSO
ACCOMPANIED BY UPPER JETS...WHICH WILL PLAY A ROLE IN ENHANCING
CONVECTION IN PARAGUAY...NORTHEAST ARGENTINA...URUGUAY AND
SOUTHERN BRASIL. A REMARKABLE ASPECT OF THIS TROUGH IS THE COLD
AIR MASS ASSOCIATED WITH IT. THIS REFLECTS IN 1000-500 HPA
THICKNESS VALUES BELOW 5340 GPM EXTENDING CROM CENTRAL PATAGONIA
NORTH INTO SAN JUAN AND NORTHERN CORDOBA IN CENTRAL ARGENTINA.
MODELS ARE SHOWING SUCH THICKNESS VALUES PROPAGATING AS FAR AS RIO
GRANDE DO SUL/SANTA CATARINA AND CORRIENTES BY SATURDAY/EARLY
SUNDAY. ASIDE FROM VERY LOW TEMPERATURES...THE PASSAGE OF THE
TROUGH AND ASSOCIATED SURFACE FRONTS WILL FAVOR MODERATE TO
LOCALLY HEAVY PRECIPITATION AS THEY INTERACT WITH A MOIST PLUMME
BREWING ACROSS PARAGUAY/NORTHEAST ARGENTINA INTO THE RIO DE LA
PLATA REGION.
IN TERMS OF FRONTAL POSITIONS...A FRONT IS FORECAST TO EXTEND
ACROSS RIO GRANDE DO SUL...WEST PARAGUAY...SOUTHERN BOLIVIA BY
WEDNESDAY EVENING. SIMULTANEOUSLY...EXPECT CYCLOGENESIS IN THE
BUENOS AIRES PROVINCE TO UNDULATE ANOTHER FRONT EXTENDING FROM A
LOW NEAR MAR DEL PLATA INTO A FRONT ACROSS CENTRAL URUGUAY...CHACO
IN ARGENTINA. AS THE POLAR HIGH BUILDS...THE SYSTEMS ARE EXPECTED
TO MOVE NORTHEAST AND MERGE BY FRIDAY. BY FRIDAY EVENING EXPECT
THE FRONT ACROSS SOUTHERN SAO PAULO IN BRASIL...SOUTHWEST MATO
GROSSO INTO NORTH-CENTRAL BOLIVIA. ON WEDNESDAY EXPECT THE LARGEST
ACCUMULATIONS DEVELOPING FROM CHACO...FORMOSA AND CORRIENTES IN
ARGENTINA INTO NORTHERN URUGUAY WHERE EXPECT MAXIMA OF 40-80MM AND
A MODERATE RISK FOR SEVERE CONVECTION. DOWNSTREAM ACROSS ENTRE
RIOS AND MOST OF URUGUAY EXPECT MAXIMA OF 25-50MM/DAY WITH A
MARGINAL RISK FOR SEVERE CONVECTION. IN COASTAL AREAS OF THE
BUENOS AIRES PROVINCE...ONSHORE FLOW ASSOCIATED WITH THE OCCLUDED
LOW WILL FAVOR MAXIMA OF 15-30MM. ON THURSDAY...THE LARGEST
AMOUNTS ARE EXPECTED IN CENTRAL AND SOUTHERN PARAGUAY AND THE BAJO
CHACO INTO MISIONES AND WESTERN RIO GRANDE DO SUL...WHERE EXPECT
MAXIMA OF 50-100MM/DAY AND A MODERATE RISK OF SEVERE CONVECTION.
DOWNSTREAM IN EASTERN RIO GRANDE DO SUL EXPECT MAXIMA OF 25-50MM.
ON FRIDAY...EXPECT POST FRONTAL CONVECTION IN EASTERN AND
NORTHEASTERN PARAGUAY AND PARANA-BRASIL TO PRODUCE MAXIMA OF
15-30MM/DAY WITH A MARGINAL RISK FOR SEVERITY. IN MISIONES AND
SANTA CATARINA EXPECT SIMILAR ACCUMULATION.
ALSO IN ASSOCIATION WITH THE COLD UPPER TROUGH...A LOW IS FORECAST
TO MEANDER ONSHORE FROM THE EASTERN PACIFIC INTO CENTRAL-SOUTHERN
CHILE ON WEDNESDAY THROUGH EARLY FRIDAY. THIS WILL FAVOR SNOWFALL
MAXIMA OF 20-40CM IN THE ANDES BETWEEN O HIGGINS AND NUBLE ON
WEDNESDAY WHILE SHOWERS FAVOR MAXIMA OF 15MM IN COASTAL LOCATION.
EXPECT LIGHTER ACCUMULATION ON THURSDAY.
NORTH OVER THE CONTINENT...EXPECT GENERALLY FAIR WEATHER
CONDITIONS DUE TO LIMITED AMOUNTS OF AVAILABLE MOISTURE.
GALVEZ...(WPC)
PALAVECINO...(SMN ARGENTINA)
LOPEZ...(DMH PARAGUAY)
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