Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center
 
South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1718Z Aug 02, 2018)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product


SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
118 PM EDT THU AUG 02 2018

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

MODEL DISCUSSION (VALID FROM AUG 02 AT 0000 UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS CONTINUE IN GOOD AGREEMENT ON THE EVOLUTION
OF THE FORECAST THROUGH 108-120 HRS. THE SOLUTIONS THEN
DRIFT...AND UNCERTAINTY IS PARTICULARLY SIGNIFICANT WITH THE
EVOLUTION OF A POTENT UPPER TROUGH CROSSING THE ANDES OF CENTRAL
CHILE/ARGENTINA ON TUESDAY.

POTENT UPPER TROUGH IS FORECAST TO RAPIDLY CROSS THE ANDES OF
SOUTHERN CHILE ON THURSDAY. THIS ASSOCIATES WITH A DEEP SURFACE
CYCLONE FORECAST TO CROSS THE DRAKE PASSAGE ON LATE THURSDAY TO
ARRIVE IN THE ANTARCTIC PENINSULA ON SATURDAY MORNING. THIS WILL
LEAD TO MODERATE PRECIPITATION ON FRIDAY...WHICH WILL SUSTAIN
ACCUMULATIONS OF 20-30MM/DAY WITH THE RISK OF ISOLATED EMBEDDED
THUNDERSTORMS BETWEEN CHILOE AND TAITAO. THE NEXT ROUND OF
SIGNIFICANT WEATHER FOR CHILE IS FORECAST TO DEVELOP LATE ON
FRIDAY AS A SUBTROPICAL MOISTURE CONNECTION ARRIVES FROM THE WEST.
AS PRECIPITATION STARTS INCREASING LATE ON FRIDAY...THROUGH EARLY
SUNDAY EXPECTING ALREADY ACCUMULATIONS OF 20-40MM/DAY BETWEEN
OSORNO/VALDIVIA INTO THE TAITAO PENINSULA. BY SATURDAY...AN
ENHANCEMENT OF CONVECTIVE INSTABILITY WILL SUSTAIN ISOLATED
THUNDERSTORMS.

A POTENT TROUGH ARRIVES ON SUNDAY/MONDAY. THIS TROUGH WILL ARRIVE
WITH UPPER JET DYNAMICS FAVORABLE FOR STRONG ASCENT AND MODERATE
SNOWFALL IN THE CENTRAL ANDES OF CHILE. AS MOISTURE WILL BE
AVAILABLE...EXPECTING A PEAK IN ACCUMULATIONS BETWEEN ARAUCANIA
AND NORTHERN AYSEN...WHERE EXPECTING MAXIMA OF 25-50MM/DAY AND
EMBEDDED THUNDERSTORMS. IN THE ANDES BETWEEN OHIGGINS AND BIO
BIO...ENHANCED UPPER DIVERGENCE UNDER A 130+ UPPER JET WILL
STIMULATE MOUNTAIN SNOWFALL TO SUSTAIN ACCUMULATIONS OF 25-50CM OF
SNOW FROM MONDAY THROUGH TUESDAY.

NORTH ACROSS THE CONTINENT...A FRONT IS MEANDERING BETWEEN CENTRAL
BOLIVIA...MATO GROSSO DO SUL...SOUTHERN MINAS GERAIS. UPPER JET
DYNAMICS WILL BE FAVORABLE TO CONTINUE SUSTAINING MODERATE
RAINFALL ACCUMULATIONS ALONG THE FRONT...TO BE FURTHER ENHANCED BY
SHORT-WAVE UPPER TROUGHS PROPAGATING FROM THE WEST. A WEAK TROUGH
CROSSING THE ANDES WILL LEAD TO AN INCREASE IN AMOUNTS BY
THURSDAY-FRIDAY ACROSS EASTERN PARAGUAY/MATO GROSSO DO
SUL/PARANA...TO SUSTAIN MAXIMA OF 20-35MM/DAY THROUGH SATURDAY. BY
FRIDAY-SATURDAY...STRONGEST CONVECTION ORGANIZES IN SOUTHEASTERN
BRASIL...TO SUSTAIN MAXIMA OF 30-60MM/DAY. BY SATURDAY-SUNDAY...AS
NEW TROUGH APPROACHES FROM THE WEST...POSITIVE INTERACTION WITH
MOIST PLUME AND SURFACE FRONT WILL DEVELOP IN SOUTHERN
PERU/CENTRAL BOLIVIA WHERE EXPECTING AMOUNTS OF 30-60MM/DAY.
CONVECTION WILL DEVELOP LATE ON SATURDAY/EARLY ON SUNDAY ACROSS
SOUTHEASTERN BOLIVIA/PANTANAL TO SUSTAIN ISOLATED MAXIMA OF
20-30MM/DAY. BY SUNDAY-MONDAY...LARGEST RAINFALL ACCUMULATIONS
WILL CLUSTER ACROSS MATO GROSSO DO SUL INTO WESTERN SAU PAULO
WHERE EXPECTING MAXIMA OF 25-50MM/DAY.

NORTH OVER THE CONTINENT...STRONGEST CONVECTION IS CLUSTERING IN
EXTREME NORTHERN SOUTH AMERICA IN ASSOCIATION WITH THE ITCZ/NET.
AN UNSEASONABLY DEEP MOIST POOL IN THE WESTERN AMAZON WILL
INTERACT WITH THE NORTHERN DIVERGENT TIER OF THE UPPER RIDGE TO
SUSTAIN SCATTERED CONVECTION IN WESTERN
BRASIL-COLOMBIA-ECUADOR-NORTHERN PERU. THIS WILL SUSTAIN MAXIMA OF
15-25MM/DAY THROUGH EARLY SATURDAY...DECREASING AFTER.

SANCHEZ...SMN (ARGENTINA)
GALVEZ...WPC (USA)