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South American Forecast Discussion
 
(Latest Discussion - Issued 1717Z Aug 28, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
117 PM EDT THU AUG 28 2014

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

MODEL DISCUSSION (VALID FROM AUGUST 28 AT 00UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS ARE IN BETTER AGREEMENT WITH RESPECT TO
YESTERDAY IN FORECAST EVOLUTION. THIS IS TRUE ESPECIALLY OVER THE
EASTERN PACIFIC...WHEN THEY NOW CROSS A SHORT WAVE ACROSS CENTRAL
CHILE ON DAYS 04 AND 05.

BLOCKING RIDGE WILL DOMINATE THE FORECAST CYCLE AS IT SITS OVER
THE SOUTHERN CONE. THIS WILL LIMIT THE PROGRESSION OF FRONTS
ACROSS SOUTHERN CHILE...LIMITING ACTIVITY TO EXTREME SOUTHERN
TIERRA DEL FUEGO AND PORTIONS OS SOUTH-CENTRAL CHILE/NORTHEASTERN
ARGENTINA. INITIALLY...RIDGE WILL DOMINATE MOST OF THE CONTINENT
FROM BRASIL/PARAGUAY SOUTH INTO THE ANTARCTIC PENINSULA. A LONG
WAVE TROUGH WITH NUMEROUS SHORT WAVE VORTICES IS MEANDERING OVER
THE EASTERN PACIFIC. STEERING FLOW OFF/OVER THE COASTS OF
CENTRAL/SOUTHERN CHILE WILL BE FROM THE NORTH. THIS IS LIMITING
THE POTENTIAL IMPACT OF SYSTEMS IN CONTINENTAL AREAS. SHOWERS WILL
LEAD TO MAXIMA OF 05-10MM/DAY THROUGH 36 HRS FROM CONCEPCION TO
THE SOUTH INTO THE ISLA CHILOE REGION. BY 36-60 HRS...A SHORT WAVE
TROUGH AND ASSOCIATED LOW-LEVEL MOISTURE CONVERGENCE WILL
STIMULATE ACTIVITY IN THE SAME REGION PRODUCING ISOLATED MAXIMA OF
15-25MM/DAY. MAXIMA OF 05-10MM/DAY IS EXPECTED FURTHER NORTH INTO
TALCA/CURICO. THE NEXT ROUND OF ACTIVITY IN CHILE IS EXPECTED INTO
DAY 04...WHEN SHORT WAVE TROUGH WILL APPROACH CENTRAL CHILE AND
LEAD TO MAXIMUM ACCUMULATIONS OF 10-15MM/DAY FROM THE SANTIAGO
REGION SOUTH INTO CONCEPCION/LOS ANGELES.

TO THE EAST...QUIET PATTERN IN ARGENTINA WILL BE INTERRUPTED ON
DAY 03 AS SHORT WAVE TROUGH CROSSES THE ANDES. THIS WILL STIMULATE
ACTIVITY IN PARAGUAY/CORRIENTES/MISIONES INTO PARTS OF SOUTHERN
BRASIL TO PRODUCE MAXIMA OF 15-25MM/DAY. SIMILAR AMOUNTS ARE
EXPECTED ON DAY 04...EXTENDING INTO THE SAO PAULO REGION.

LIGHT CONVECTION WILL PRODUCE SHOWERS ACROSS EXTREME SOUTHEASTERN
BRASIL IN ASSOCIATION WITH A FRONT THAT IS BECOMING STATIONARY.
ACTIVITY WILL CONCENTRATE ACROSS RIO DO JANEIRO/ESPIRITO SANTO
WITH MAXIMA OF 05-10MM/DAY THROUGH 60 HRS.

TO THE WEST...AS LONG WAVE UPPER TROUGH APPROACHES PERU/NORTHERN
CHILE FROM THE SOUTHWEST...EXPECTING UPPER DIVERGENCE TO INCREASE
AND STIMULATE DIURNAL CONVECTION OVER THE ANDES. AN UNSEASONABLY
MOIST AIR MASS REMAINS OVER THE WESTERN AMAZON BASIN. THIS WILL
LEAD TO SCATTERED STORMS ACROSS WESTERN AMAZONIA WITH MAXIMA OF
15-30MM/DAY THROUGH 36HRS...AND 15-20MM/DAY BY 36-60 HRS. ALONG
THE CENTRAL ANDES...EXPECTING ALSO AN ENHANCEMENT IN ACTIVITY WITH
MAXIMA OF 05-10MM/DAY THROUGH 84 HRS...AND THE RISK FOR SNOW
SHOWERS IN HIGHER ELEVATIONS ESPECIALLY BY 36-84 HRS.

JALFIN...SMN (ARGENTINA)
CAROCA...DMC (CHILE)
GALVEZ...WPC (USA)