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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 2009Z Jun 28, 2024)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
409 PM EDT FRI JUN 28 2024

GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/

SOUTH AMERICAN DISCUSSION FOR 28 JUN 2024 AT 19 UTC: A SYSTEM OF
INTEREST IS AN ATMOSPHERIC RIVER FORECAST TO ARRIVE IN CHILE
AUSTRAL ON SATURDAY. NOTE THAT THE MOIST PLUME IS FORECAST TO
REACH PRECIPITABLE WATER VALUES OF 20-25MM AND IS EXPECTED TO
ARRIVE INTO MAGALLANES/AYSEN ACOMPANIED BY 30-45KT NORTHWESTERLY
WINDS AT 850 HPA. ALTHOUGH ENHANCEMENT BY UPPER JET DYNAMICS IS
EXPECTED WELL TO THE NORTH OF THESE REGIONS...TWO NEGATIVELY
TILTED SHORT WAVE MID-LEVEL TROUGHS ARE LIKELY TO PROVIDE TWO
PERIODS OF DYNAMICAL ENHANCEMENT. EXPECT ACCUMULATION OF
15-20MM/DAY AND LOCALIZED MAXIMA OF 30-60MM IN REGIONS OF
TOPOGRAPHICAL FORCING FROM SATURDAY MORNING INTO SUNDAY MORNING.
DURING SUNDAY...WIND DIRECTIONS ARE FORECAST TO BECOME
SOUTHWESTERLIES ACROSS MAGALLANES/AYSEN INTO SOUTHERN PATAGONIA.
THIS WILL BRING A MUCH COOLER AIR MASS AND FAVOR A RETURN OF
SNOWFALL. HOWEVER...MODERATE ACCUMULATIONS ARE EXPECTED IN WESTERN
AND SOUTHERSTERN SLOPES OF THE ANDES...WHILE VERY LIMITED/SMALL
ACCUMULATIONS DEVELOP IN PATAGONIA. IN TERMS OF AMOUNTS...EXPECT
05-10CM/DAY AND MAXIMA OF 15CM. HOWEVER...ISOLATED HIGHER AMOUNTS
ARE EXPECTED IN HIGH ELEVATIONS.

A LARGE MID-UPPER TROUGH IN THE SOUTH ATLANTIC CONTINUES TO FAVOR
COLD AND WINDY CONDITIONS ALONG THE CENTRAL COAST OF ARGENTINA AND
URUGUAY. THIS ALSO ASSOCIATED WITH A POLAR HIGH DEVELOPING IN
INTERIOR PORTIONS OF CENTRAL ARGENTINA ON FRIDAY. THE SYSTEM
ASSOCIATED WITH A LONG-FETCH SURFACE FRONT THAT BY FRIDAY EVENING
IS EXPECTED ACROSS PARANA-BRASIL...THE PANTANAL...AND SANTA CRUZ
DE LA SIERRA IN BOLIVIA. AS THE SURFACE HIGH BUILDS IN NORTHEAST
ARGENTINA ON SATURDAY...EXPECT THE FRONT TO CONTINUE ADVANCING
NORTHWARD. BY SATURDAY EVENINT IT IS EXPECTED ACROSS EASTERN RIO
DE JANEIRO...WESTERN MINAS GERAIS...CENTRAL MATO GROSSO...NORTHERN
BOLIVIA. BY SUNDAY EVENING EXPECT THE FRONT ALONG ESPIRITO
SANTO-BRASIL...AND A WEAKENING/FRONTOLIZING BOUNDARY ACROSS
SOUTHWEST BRASIL INTO CENTRAL PERU. IN TERMS OF
PRECIPITATION...THROUGH EARLY SATURDAY EXPECT 05-10MM/DAY AND
MAXIMA OF 15-20MM IN POST FRONTAL REGIONS ACROSS PARANA/SANTA
CATARINA IN BRASIL...INTO MOST OF PARAGUAY. IN CENTRAL BOLIVIA
EXPECT MAXIMA OF 15-30MM ALONG THE ANDES. BY SATURDAY THROUGH
EARLY SUNDAY EXPECT MAXIMA OF 15-25MM IN SAO PAULO AND RIO DE
JANEIRO IN BRASIL...WHILE IN SOUTHERN PERU/NORTHWEST BOLIVIA
EXPECT MAXIMA OF 20-35MM IN FRONTAL CONVECTION. ON SUNDAY...EXPECT
MAXIMA OF 15-25MM IN ESPIRITO SANTO-BRASIL IN FRONTAL CONVECTION.
IN SAO PAULO/RIO DE JANEIRO...THE RIGHT ENTRANCE OF AN UPPER JET
WILL STIMULATE THE DEVELOPMENT OF THUNDERSTORMS TO FAVOR SIMILAR
AMOUNTS. WEST ACROSS CENTRAL PERU...UPSLOPE NORTH OF THE WEAKENING
BOUNDARY WILL FAVOR MAXIMA OF 20-35MM.

IN TROPICAL SOUTH AMERICA...SEASONALLY DRY CONDITIONS ARE EXPECTED
TO CONTINUE...AS HEAVY PRECIPITATING SYSTEMS CLUSTER IN LATITUDES
TO THE NORTH OF 05N.

GALVEZ..(WPC)
PALAVECINO (SMN-ARGENTINA)
SARABIA (DMC-CHILE)