Prognostic Meteorological Discussion
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FXSA20 KWBC 311528
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1127 AM EDT TUE MAY 31 2016

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

MODEL DISCUSSION (VALID FROM MAY 31 AT 0000 UTC): CONFIDENCE IN
THE FORECAST IS HIGH THROUGH 96-108 HRS...WITH MODELS THEN
DIVERGING ON SHORT WAVE PATTERN EVOLUTION DURING THE LATTER PART
OF THE FORECAST.

THE NORTHERN STREAM PATTERN ACROSS THE EASTERN PACIFIC IS TO
REMAIN ACTIVE AS SUCCESSIVE MID/UPPER LEVEL PERTURBATIONS STREAM
TOWARD CENTRAL/NORTHERN PORTIONS OF CHILE...WITH A SUBTROPICAL JET
MAXIMA TO BOUND THE NORTHERN FRINGES OF THE TROUGH AS IT MEANDERS
INTO CHILE. THESE ARE TO FOCUS THEIR SHORT WAVE ENERGY ACROSS THE
CONTINENT BETWEEN 20S-40S...WHILE THE JET ALOFT IS TO FAVOR A
DIVERGENT PATTERN. THE INFLOW OF SHORT WAVE ENERGY WILL BE
ACCOMPANIED BY A TONGUE OF SUBTROPICAL MOISTURE. THIS WILL COMBINE
WITH ABOVE NORMAL SEA SURFACE TEMPERATURES TO LIKELY FAVOR HEAVY
PRECIPITATION AMOUNTS. AT LOW LEVELS...AN ELONGATED FRONT MEANDERS
EAST INTO CENTRAL CHILE BY 66-72 HRS...WHERE IT IS TO REMAIN
THROUGH 108-120 HRS. THIS IS TO FAVOR A LOW LEVEL CONVERGENT
PATTERN THAT IS TO SUSTAIN GENERATION OF HEAVY RAINS WITH EMBEDDED
THUNDERSTORMS. THE MOST INTENSE IS EXPECTED BETWEEN VALPARAISO TO
JUST NORTH OF LA SERENA ON THURSDAY AFTERNOON THROUGH SATURDAY
MORNING. ON THURSDAY TO FRIDAY EXPECTING MAXIMA OF
25-50MM...INCREASING TO 50-100MM ON FRIDAY TO SATURDAY. THIS IS TO
ALSO SUSTAIN HEAVY SNOWFALL AMOUNTS ACROSS THE CENTRAL
ANDES...WITH DAILY ACCUMULATION OF 50-100CM AND LOCALIZED MAXIMA
OF 150CM.

BROAD MID/UPPER LEVEL TROUGH ENVELOPS CONTINENTAL AREA BETWEEN
20S-45S. THIS IS TO SLOWLY PULL TO THE EAST-SOUTHEAST AS THE
AFOREMENTIONED PERTURBATIONS STREAM ACROSS THE EASTERN PACIFIC TO
CHILE/WESTERN ARGENTINA. EARLY IN THE CYCLE THE TROUGH IS TO
ANCHOR ON TWO LOWS...WITH ONE TO CENTER JUST WEST OF CONCEPCION
CHILE WHILE THE OTHER MEANDERS OVER THE BUENOS AIRES PROVINCE.
THROUGH 60-66 HRS THESE ARE TO SLOWLY PULL TO THE EAST-SOUTHEAST.
AT LOW LEVELS THIS IS TO SUSTAIN A BROAD OCCLUDED TROUGH OVER THE
WESTERN ATLANTIC/CENTRAL ARGENTINA...WITH A SURFACE FRONT
MEANDERING ACROSS SAO PAULO TO MATO GROSSO DO SUL/SANTA CRUZ IN
EASTERN BOLIVIA. UNDER INFLUENCE OF THE OCCLUDED LOW...HEAVY RAINS
ARE TO AFFECT SOUTHERN BUENOS AIRES PROVINCE/LA PAMPA THROUGH 36
HRS WITH MAXIMA OF 25-50M THROUGH 36 HRS...AND 15-30MM AT 36-60
HRS. THIS DECREASES TO TRACE AMOUNTS BY 72-84 HRS. ALONG THE
MEANDERING FRONT...MEANWHILE... INITIALLY EXPECTING MAXIMA OF
15-25MM BETWEEN MATO GROSSO AND SAO PAULO IN BRASIL. BY 36-108 HRS
THIS IS TO INCREASE TO 20-40MM/DAY...WHILE OVER EASTERN-CENTRAL
BOLIVIA IT IS TO PEAK AT 10-15MM.

NORTH OVER THE CONTINENT...AT 200 HPA...BROAD CELL OF THE
SUBEQUATORIAL RIDGE IS TO EXTEND WEST ACROSS EQUATORIAL SOUTH
AMERICA TO THE EASTERN TROPICAL PACIFIC. THROUGH 72-96 HRS THE
RIDGE PATTERN ALOFT IS TO STRENGTHEN...TIGHTENING THE GRADIENT AS
IT PRESSES AGAINST A BROAD TROUGH TO THE SOUTH. THE RIDGE ALOFT IS
TO VENT DEEP CONVECTION ACROSS BRASIL-PERU TO THE NORTH OF
10S...WITH MAXIMA TO PEAK AROUND 15-25MM. THROUGH 96-120 HRS
CONVECTION ACROSS NORTHERN AMAZONAS-RORAIMA IN BRASIL TO SOUTHERN
COLOMBIA IS FORECAST TO INTENSIFY AS UPPER LEVEL RIDGE PATTERN
STRENGTHENS OVER THE CONTINENT...WITH DAILY MAXIMA INCREASING TO
20-35MM.

AYALA...DINAC (PARAGUAY)
DAVISON...WPC (USA)

$$





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