324
FXSA20 KWBC 232019
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
418 PM EDT MON SEP 23 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 23 SEP 2024 AT 20 UTC:
THE UPPER LEVEL ANALYSIS SHOWS A BROAD UPPER TROUGH EXTENDING
ACROSS THE SOUTHERN CONE...SOUTHWEST SOUTH AMERICA INTO THE
EASTERN PACIFIC NEAR 20S 95W. THIS TROUGH IS PRESSING AGAINST A
CELL OF THE SUBTROPICAL UPPER RIDGE THAT CENTERS OVER NORTHERN
BOLIVIA. THE HIGH EXTENDS AN AXIS INTO SOUTHERN BRASIL...WHICH IS
YIELDING TO AN ELONGATED UPPER JET FROM 25S 88W...THROUGH CENTRAL
CHILE INTO 40S 50W. IN THE MID-LEVELS...A BLOCKING MID-LEVEL RIDGE
IS PRESENT IN SOUTHERN BRASIL...PARAGUAY...BOLIVIA. AS THIS RIDGE
PERSISTS...IT WILL LIMIT THE NORTHWARD PROGRESSION OF FRONTS INTO
MID-SECTIONS OF THE CONTINENT THROUGH WEDNESDAY. IN THE LOW
LEVELS...A BOUNDARY THAT EXTENDS ACROSS SOUTHERN RIO GRANDE DO
SUL...NORTHEAST ARGENTINA...FORMOSA/SALTA IN NORTHWEST ARGENTINA.
THE SALLJ IS PRESENT...AND IS FAVORING MOISTURE CONVERGENCE IN THE
COOL SIDE OF THE BOUNDARY...ACROSS PORTIONS OF NORTHEAST
ARGENTINA...URUGUAY AND FAR SOUTHERN BRASIL. MOST CONVECTION IS
DEVELOPING IN THESE REGIONS AND BECOMING MARGINALLY SEVERE AIDED
BY COOL MID-LEVEL TEMPERATURES.
GIVEN THE QUASI-STATIONARY NATURE OF THE MID-UPPER FLOW PATTERN
THROUGH WEDNESDAY...EXPECT RECURRENT FORMATION OF HEAVY RAIN
PRODUCING THUNDERSTORMS ACROSS NORTHEAST ARGENTINA...CENTRAL AND
NORTHERN URUGUAY...AND FAR SOUTHERN BRASIL...FAVORING TWO-DAY
STORM TOTAL AMOUNTS IN THE 100-200MM RANGE. ON MONDAY...EXPECT THE
LARGEST AMOUNTS TO CLUSTER BETWEEN NORTHERN ENTRE
RIOS...CENTRAL-NORTHERN URUGUAY AND SOUTHERN RIO GRANDE DO SUL.
EXPECT ACCUMULATION OF 20-40MM/DAY AND MAXIMA OF 50-100MM WITH A
MODERATE RISK FOR SEVERITY. ON TUESDAY...EXPECT 15-30MM/DAY AND
MAXIMA OF 75-125MM IN THE SAME REGION...INCLUDING A MODERATE RISK
FOR SEVERITY. ON WEDNESDAY...AS AN UPPER TROUGH STARTS CROSSING
THE ANDES...EXPECT THE SURFACE FRONT TO START MEANDERING
NORTHWARD. THIS WILL LEAD TO A NORTHWARD RELOCATION OF THE AREA OF
HEAVIEST PRECIPITATION TO CORRIENTES...NORTHERN AND CENTRAL RIO
GRANDE DO SUL...WHERE EXPECT MAXIMA OF 35-70MM WITH A SLIGHT RISK
FOR SEVERITY.
ALSO OF INTEREST...ENHANCED WESTERLY FLOW IN FAR SOUTHERN CHILE
WILL FAVOR MODERATE PRECIPITATION THROUGH THE CYCLE. GIVEN THE
PRESENCE OF A COLD AIR MASS WITH 1000-500 THICKNESS NEAR AND BELOW
5280 GPM SOUTH OF 48S...EXPECT PERIODS OF MODERATE SNOWFALL. ON
MONDAY EXPECT SNOW ACCUMULATION OF 20-35CM IN ELEVATED TERRAIN OF
AYSEN AND IN WESTERN MAGALLANES. THIS DECREASES TO MAXIMA OF
10-20CM ON TUESDAY. ON WEDNESDAY EXPECT AN INCREASE IN AREAS PRONE
TO RAINFALL WITH FORECAST MAXIMA OF 30-60MM FROM NORTHERN
MAGALLANES INTO SOUTHERN AYSEN. STILL...EXPECT SNOW IN HIGH
ELEVATIONS.
GALVEZ...(WPC)
TINOCO...(WPC)
LOPEZ...(DMH-PARAGUAY)
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