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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1638Z Sep 24, 2018)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1238 PM EDT MON SEP 24 2018

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

MODEL DISCUSSION (VALID FROM SEP 24 AT 0000 UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS ARE IN FAIRLY GOOD AGREEMENT THROUGH 84
HRS...WHEN CONFIDENCE STARTS DECREASING RAPIDLY. THE ECMWF AND
UKMET MODELS ARE IN BETTER AGREEMENT ON THE EVOLUTION OF THE LONG
WAVE PATTERN...WHICH SUGGESTS AN ANTARCTIC INCURSION FOR THE
SOUTHERN CONE DURING DAYS 05 AND 06. YET...CONFIDENCE IS STILL LOW.

BROAD TROUGH EXTENDS TO THE WEST OF THE CENTRAL ANDES. THIS IS
SHEARING A SHORT WAVE TROUGH THAT IS FORECAST TO CROSS BOLIVIA
INTO PARAGUAY DURING LATE HOURS OF MONDAY. THIS WILL INTERACT WITH
SURFACE FRONT LINGERING IN MID-SECTIONS OF THE CONTINENT TO
SUSTAIN ANOTHER ROUND OF STRONG CONVECTION IN THE ARGENTINEAN
CHACO AND CORRIENTES/WESTERN RIO GRANDE DO SUL ON LATE MONDAY INTO
EARLY HOURS OF TUESDAY. EXPECTING MAXIMA OF 50-100MM/DAY WITH THE
RISK OF MCS FORMATION. IN PARAGUAY-SANTA CATARINA/EASTERN RIO
GRANDE DO SUL EXPECTING MAXIMA OF 20-35MM. BY
TUESDAY-WEDNESDAY...EXPECTING ANOTHER ROUND OF STRONG EARLY
MORNING CONVECTION IN CORRIENTES-ARGENTINA TO SUSTAIN MAXIMA OF
50-100MM/DAY. UPSTREAM ACROSS PARAGUAY...EXPECTING MAXIMA OF
25-50MM. BY WEDNESDAY-THURSDAY...EXPECTING ACCUMULATIONS OF
20-30MM/DAY ACROSS SOUTHEASTERN PARAGUAY AND NORTHEASTERN
ARGENTINA/SOUTHERN MATO GROSSO DO SUL IN BRASIL. AFTER THIS
PERIOD...CONFIDENCE ON THE EVOLUTION OF PRECIPITATION IN
MID-SECTIONS OF THE CONTINENT DECREASES.

TO THE SOUTH...AN UPPER TROUGH AND ASSOCIATED SURFACE FRONTS WILL
ARRIVE INTO SOUTHERN CHILE ON MONDAY. THIS WILL SUSTAIN
ACCUMULATIONS OF 10-15MM/DAY WITH THE RISK OF EMBEDDED
CUMULONIMBUS. ALSO...AS EASTERLY FLOW DEVELOPS IN SOUTHERN
PATAGONIA...EXPECTING SIMILAR ACCUMULATIONS THROUGH EARLY TUESDAY.
THE NEXT ROUND OF SIGNIFICANT PRECIPITATION FOR CHILE IS EXPECTED
TO START UNRAVELING ON THURSDAY TO PEAK BETWEEN FRIDAY AND
SATURDAY. THE EXACT TIMING AND EXPECTED ACCUMULATIONS ARE STILL
UNCERTAIN GIVEN LACK OF CONFIDENCE ON THE SOLUTIONS. YET...UNDER
THE AMPLIFICATION OF AN UPPER TROUGH OFF THE COASTS OF CHILE AS
LONG-FETCH SOUTHERLY FLOW DEVELOPS...EXPECTING A NORTHWARD
AMPLIFICATION OF THE UPPER TROUGH AND ASSOCIATED UPPER JETS BY
FRIDAY. THIS WILL LEAD TO ENHANCED UPPER DYNAMICS TO SUSTAIN
MODERATE PRECIPITATION IN AREAS BETWEEN BIO BIO AND LOS LAGOS ON
THURSDAY THROUGH SATURDAY...AND MOUNTAIN SNOWFALL DEVELOPING
ESPECIALLY DURING THE WEEKEND. PRELIMINARY QPF SUGGESTS
ACCUMULATIONS INCREASING TO MAXIMA OF 15-20MM/DAY BETWEEN BIO BIO
AND LOS LAGOS ON THURSDAY-FRIDAY...PEAKING AT MAXIMA OF
20-35MM/DAY BETWEEN SOUTHERN MAULE AND LOS LAGOS ON
FRIDAY-SATURDAY.

SANCHEZ...SMN (ARGENTINA)
SALAZAR...SENAMHI (BOLIVIA)
GALVEZ...WPC (USA)