971
FXSA20 KWBC 191909
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
309 PM EDT MON AUG 19 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 19 AUG 2024 AT 19 UTC:
A SYSTEM OF INTEREST IS AN UPPER TROUGH OFF THE COAST OF SOUTHERN
CHILE...WHICH IS BECOMING CUTOFF ON MONDAY. THE LOW HAS VERY COLD
TEMPERATURES NEAR THE CENTER...REFLECTING IN 1000-500 HPA
THICKNESS UNDER 5280 GPM. THE COLD CORE IS FAVORING THUNDERSTORMS
OFF THE COAST OF SOUTHERN CHILE...BUT MOST IMPORTANTLY...IS
ENHANCING VENTILATION ACROSS THE ANDES OF CENTRAL AND SOUTHERN
ARGENTINA AND CHILE. IN THE LOW-LEVELS...THE PRESENCE OF A POLAR
HIGH IN CENTRAL PATAGONIA IS FAVORING EASTERLY FLOW ACROSS
PORTIONS OF CENTRAL ARGENTINA. THIS IS HIGHLIGHTING MOISTURE
CONVERGENCE EAST OF THE ANDES. THIS IS RESULTING IN SCATTERED TO
WIDESPREAD LIGHT PRECIPITATION FROM SAN JUAN AND MENDOZA SOUTH
INTO PORTIONS OF NEUQUEN AND WESTERN RIO NEGRO IN ARGENTINA. COLD
TEMPERATURES IS YIELDING TO SCATTERED SNOWFALL...ESPECIALLY ALONG
AND EAST OF THE ANDES. THE UPPER TROUGH IS FORECAST TO MOVE VERY
LITTLE THROUGH WEDNESDAY...TO THEN CROSS THE ANDES THROUGH
THURSDAY EVENING. THIS SLOW-TO-EVOLVE SYSTEM WILL PROLONG THE
EVENT IN ARGENTINA. THROUGH EARLY TUESDAY...EXPECT SNOWFALL
REACHING 05-10CM/DAY AND ISOLATED MAXIMA OF 15-20CM IN NORTHERN
NEUQUEN/SOUTHERN MENDOZA. NORTH INTO SAN JUAN AND SAN LUIS EXPECT
05-10MM/DAY AND ISOLATED MAXIMA OF 15MM. ON TUESDAY...EXPECT THE
CORE OF THE EVENT TO MOVE EAST INTO LA PAMPA/SOUTHERN SAN LUIS
WHERE EXPECT 05-10MM/DAY AND ISOLATED MAXIMA OF 15-20MM WITH A
RISK OF MIXED PRECIPITATION BUT LITTLE SNOW ACCUMULATION. NOTE
THAT SNOWFALL IS STILL EXPECTED IN THE CORDILLERA...WHERE MAXIMA
OF 15-25CM/DAY IS FORECAST BETWEEN 31S AND 36S...WHILE NORTH INTO
27S EXPECT MAXIMA UNDER 15CM/DAY. ALSO ON TUESDAY...EXPECT COASTAL
CONVECTION BETWEEN O'HIGGINS IN CHILE AND ARAUCANIA...TO FAVOR
05-10MM/DAY AND ISOLATED MAXIMA OF 15-20MM. ON WEDNESDAY...AS THE
SURFACE LOW ENTERS CENTRAL CHILE...EXPECT SCATTERED AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15MM FROM VALPARAISO INTO BIO BIO. IN
THE ADJACENT CORDILLERA...EXPECT ADDITIONAL SNOWFALL AMOUNTS OF
15-30CM/DAY.
IN MID-PORTIONS OF THE CONTINENT...A STATIONARY FRONT EXTENDS FROM
SOUTH BRASIL ACROSS THE PARAGUAY-ARGENTINA BORDER INTO SOUTHERN
BOLIVIA. A NARROW ATMOSPHERIC RIVER OF 30-40MM EXTENDS ACROSS THE
BOUNDARY...WHICH IS FAVORING SCATTERED CONVECTION IN RIO GRANDE DO
SUL-BRASIL. AS THE AFOREMENTIONED UPPER TROUGH IN THE EASTERN
PACIFIC STARTS TO APPROACH THE ANDES...EXPECT A GRADUAL INCREASE
IN VENTILATION AND THE SHEARING OF CYCLONIC VORTICITY INTO
PORTIONS OF ARGENTINA. THIS WILL FAVOR A STREGNTHENING OF THE
SALLJ AND DEEP-LAYER MOISTURE TRANSPORT INTO PORTIONS OF
NORTH-CENTRAL ARGENTINA. THROUGH EARLY TUESDAY...CONVECTION ALONG
THE FRONT WILL FAVOR MAXIMA OF 20-35MM/DAY AND A SLIGHT RISK OF
SEVERITY FROM CORRIENTES INTO SOUTHERN RIO GRANDE DO SUL/NORTHERN
URUGUAY. ISENTROPIC LIFT WILL INTERACT WITH THE APPROACHING UPPER
TROUGH AND MAXIMA OF 30-60MM/DAY IN CORRIENTES...ENTRE RIOS...MOST
OF URUGUAY AND SOUTHERN RIO GRANDE DO SUL...INCLUDING A SLIGHT
RISK FOR SEVERITY. LIGHTER PRECIPITATION IS EXPECTED ACROSS THE
NORTHERN BUENOS AIRES PROVINCE AND SANTA FE WITH MAXIMA UNDER
15-20MM. ON WEDNESDAY...THE SURFACE FRONT IS FORECAST TO START
MEANDERING NORTHWARD. BY THE EVENING EXPECT IT ALONG CENTRAL RIO
GRANDE DO SUL...SOUTHEAST PARAGUAY...SOUTHERN BOLIVIA. EXPECT THE
HEAVIEST PRECIPITATION IN THE COLD SIDE OF THE
FRONT...PARTICULARLY BETWEEN CHACO/FORMOSA IN ARGENTINA INTO
CORRIENTES...NORTHERN ENTRE RIOS AND NORTHERN URUGUAY/WESTERN RIO
GRANDE DO SUL. EXPECT MAXIMA OF 40-80MM WITH A MODERATE RISK FOR
SEVERITY. ALONG SOUTHERN URUGUAY AND THE EASTERN BUENOS AIRES
PROVINCE EXPECT MAXIMA OF 15MM AS THE OCCLUDED LOW EXITS THE COAST
HIGHLIGHTING ONSHORE EASTERLY FLOW.
NORTH OVER THE CONTINENT THE DRY SEASON CONTINUES. GIVEN VERY
LIMITED AVAILABLE MOISTURE...EXPECTING LIGHT PRECIPITATION TO
CLUSTER IN PORTIONJS OF THE NORTHERN AMAZON BASIN AND DEVELOP IN A
VERY ISOLATED MANNER.
GALVEZ...(WPC)
PALAVECINO...(SMN ARGENTINA)
LOPEZ...(DMH PARAGUAY)
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