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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1516Z May 26, 2020)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1116 AM EDT TUE MAY 26 2020

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

FORECAST DISCUSSION FROM MAY 26/16UTC: A MID/UPPER LEVEL TROUGH ON
THE NORTHERN STREAM LIES OFF THE SOUTHEAST COAST OF BRASIL WHILE
CENTERING ON A CLOSED LOW NEAR 37S 40W. THIS IS FORECAST TO SLOWLY
PULL TO THE EAST-SOUTHEAST DURING THE NEXT 24-36 HRS...THEN
ACCELERATES LATER IN THE WEEK. AT LOW LEVELS...THIS SUSTAINS AN
ELNGATED FRONT ORIGINAITING ON A DEEP OCCLUDED LOW OFF THE SOUTH
COAST OF BRASIL...WITH BOUNDARY TRAILING ACROSS ESPIRITO SANTO IN
BRASIL TO SOUTHERN AMAZONAS. THIS SUSTAINS A PREFRONTAL SHEAR LINE
ACROSS SOUTHERN PARA TO RORAIMA/SOUTHERN VENEZUELA. THE
FRONT...AND PREFRONTAL SHEAR LINE...ARE TO PERSIST DURING THE NEXT
TWO DAYS...BUT AS THE UPPER LEVEL TROUGH MEANDERS AWAY...THEY ARE
TO GRADUALLY DISSIPATE. MEANWHILE...EXPECTING SCATTERED CONVECTION
TO CLUSTER ALONG THE SHEAR LINE...WITH ACCUMULATION OF
20-35MM/DAY. HIGHER AMOUNTS ARE EXPECTED OVER SOUTHERN VENEZUELA
TO AMAZONIA IN SOUTHERN COLOMBIA...WHERE THIS WILL SUSTAIN MAXIMA
OF 35-70MM. OTHER CONVECTION IS EXPECTED ACROSS ESPIRITO
SANTO-EASTERN BAHIA. IN THIS AREA INITIALLY EXPECTING ACCUMULATION
OF 05-10MM. ON THURSDAY-FRIDAY THIS INCREASES TO 20-40MM AS
ENHANCED BY A STRONG EAST-SOUTHEASTERLY FLOW.

UPSTREAM OVER THE EASTERN PACIFIC...A LONG WAVE TROUGH IS TO
EXTEND TO THE NORTH-NORTHWEST FROM THE BELLINGSHAUSEN SEA TO 20S
85W EARLY ON WEDNESDAY MORNING. THROUGH THURSDAY THIS IS TO SLOWLY
LIFT ACROSS SOUTHERN CHILE TO PATAGONIA IN ARGENTINA...WHILE A
SHORT WAVE TROUGH ON THE NORTHERN STREA CUTS OFF TO THE NORTH. THE
LATTER IS TO STALL OVER THE EASTERN PACIFIC OFF THE
CENTRAL/NORTHERN COAST OF CHILE...WHILE THE FORMER
AMPLIFIES/DEEPENS OVER THE WESTERN ATLANTIC. AT LOW LEVELS THIS IS
TO INITIALLY FAVOR A BROAD/LOW AMPLITUDE TROUGH OVER THE SOUTHERN
CONE...WITH A SURFACE FRONT MEANDERING ACROSS NORTHERN PATAGONIA
IN ARGENTINA-CONCEPCION IN SOUTHERN CHILE. THE FRONT IS TO REMAIN
NEARLY STATIONARY THROUGH WEDNESDAY EVENING...THEN SURGES ACROSS
CENTRAL ARGENTINA ON THURSDAY AS A FRONTAL LOW FORMS OVER
PATAGONIA/LA PAMPA. THE LOW IS TO DEEPEN/RAPIDLY OCCLUDE AS IT
MEANDERS OFF THE COAST OF ARGENTINA ON FRIDAY. BUILDING POLAR
RIDGE TO THE SOUTH WILL THEN SUSTAIN A PAMPERO LOW LEVEL JET THAT
DISPLACES THE FRONT NORTH ACROSS URUGUAY-CORDOBA IN ARGENTINA ON
FRIDAY. THIS THEN RACES ACROSS SOUTHERN BRASIL-PARAGUAY TO
SOUTHEAST BOLIVIA ON SATURDAY. OVER SOUTHERN CHILE THIS WILL
SUSTAIN SCATTERED CONVECTION DURING THE NEXT COUPLE OF DAY...WITH
MAXIMA OF 15-20MM/DAY. OVER PATAGONIA...THE OCCLUDING LOW WILL
GENERALLY FAVOR LIGHT CONVECTION ON THURSDAY...WITH MAXIMA OF
05-10MM. SIMILAR AMOUNTS ARE EXPECTED OVER SOUTHERN BUENOS AIRES
PROVINCE ON FRIDAY...WITH POTENTIAL FOR LIGHT SNOW ACROSS SIERRA
DE LA VENTANA/TANDIL. HEAVY SNOWFALL AMOUNTS...HOWEVER...ARE
EXPECTED ALONG THE CENTRAL/NORTHERN ANDES OF CHILE BETWEEN
27S-31S...WITH ACCUMULATION OF 15-20CM ON FRIDAY...AND AN
ADDITIONAL 05-10CM ON SATURDAY. AS IT SURGES ACROSS NORTHWEST
ARGENTINA TO BOLIVIA THIS WILL TRIGGER LIGHT/LOCALLY MODERATE
RAINFALL AMOUNTS...WITH MAXIMA OF 05-10MM.

DAVISON...WPC (USA)
GALVEZ...WPC (USA)