Prognostic Meteorological Discussion
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FXSA20 KWBC 291632
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1231 PM EDT FRI APR 29 2016

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

MODEL DISCUSSION (VALID FROM APR 29 AT 0000 UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS ARE IN GOOD AGREEMENT MAINTAINING LONG WAVE
PATTERN ACROSS SOUTH AMERICA THROUGH THE CYCLE. PROBLEMS ARISE ON
THE SOLUTION OF A SHORT WAVE TROUGH AMPLIFYING OVER THE
SOUTHEASTERN PACIFIC AS IT MOVES TOWARDS TIERRA DEL FUEGO
PATAGONIA AFTER 96 HRS.

UNSEASONABLE STRONG AND AMPLE POLAR TROUGH EXTENDS ALONG 55W-48W
ACROSS MOST OF SOUTHERN AND CENTRAL BRASIL. THIS TROUGH CONTINUES
SUSTAINING AN IMPRESSIVE SURFACE FRONT ACROSS CENTRAL BRASIL INTO
CENTRAL AMAZONAS-BRASIL/COLOMBIA/ECUADOR BORDER. THE BOUNDARY WILL
BECOME ILL-DEFINED DURING FRIDAY/SATURDAY IN AREAS TO THE
NORTHWEST OF PARA. TO THE EAST...A SHEAR LINE IS WELL STRUCTURED
AND IS FORECAST TO EXTEND ACROSS PARA INTO GUYANA ON FRIDAY
EVENING...WESTERN BAHIA-NORTHEASTERN PARA-SURINAME ON SATURDAY
EVENING TO THEN LOSE DEFINITION. CONVECTION IS ORGANIZED WITH SHIS
SYSTEM AND WIL CONTINUE SUSTAINING ORGANIZED CONVECTION WITH
LOCALLY HEAVY RAINFALL ACROSS NORTHERN BRASIL INTO VENEZUELA AND
GUYANA/SURINAME. THROUGH EARLY SATURDAY EXPECTING MAXIMA OF
75-125MM/DAY IN THESE REGIONS...DECREASING TO MAXIMA OF
30-60MM/DAY DURING SATURDAY INTO EARLY SUNDAY. AS THE DYNAMIC
FORCING DECREASES...EXPECTING A RESTORATION OF THE DIURNAL
CONVECTION PATTERN DURING SUNDAY AND ON. THIS WILL LEAD TO
SCATTERED MAXIMA OF 20-35MM/DAY IN NORTHERN BRASIL DURING SUNDAY
INTO MONDAY...AND MAXIMA OF 15-30MM/DAY AFTER. THE FRONT WILL ALSO
LEAD TO STRONG CONVECTION ACROSS RIO DE JANEIRO/SE MINAS GERAIS
THROUGH EARLY SATURDAY WHERE EXPECTING MAXIMA OF 20-40MM/DAY.
AMOUNTS ARE TO DECREASE TO MAXIMA OF 10-15MM/DAY ON ESPIRITO SANTO
DURING SATURDAY INTO EARLY SUNDAY.

COLD FRONT IS MOVING ACROSS THE RIO DE LA PLATA IN A REGION OF
LIMITED MOISTURE. THIS COLD FRONT WILL PROPAGATE INTO THE EASTERN
COAST OF BRASIL THROUGH THE CYCLE. THE FRONT WILL ENCOUNTER A
MOISTER AIR MASS ONCE IT REACHES THE COAST/SERRA DO MAR OF
PARANA/SAO PAULO AND AREAS TO THE NORTHEAST. THIS WILL LEAD TO
SCATTERED ACCUMULATIONS OF 00-05MM/DAY ON SATURDAY INTO SUNDAY.
DURING SUNDAY...THE FRONT WILL EXTEND INTO CENTRAL ESPIRITO SANTO
WHILE A SHEAR LINE ORGANIZES INTO SOUTHERN BAHIA. BY MONDAY
EVENING THE FRONT WILL EXTEND ACROSS CENTRAL BAHIA WHILE THE SHEAR
LINE EXTENDS INTO NORTHERN BAHIA...WHERE IT IS TO STALL AFTER.
EXPECTING A SURGE IN THE LOW-LEVEL SOUTH EASTERLIES DURING LATE
SUNDAY INTO MONDAY. THIS WILL ENHANCED LOW-LEVEL CONVERGENCE ALONG
THE COASTLINE AND ACCUMULATIONS TO TRIGGER MAXIMA OF 15-30MM/DAY
DURING SUNDAY-EARLY MONDAY AND MAXIMA OF 25-50MM/DAY DURING
MONDAY-TUESDAY.

FARTHER UPSTREAM...OVER THE PACIFIC...A BROAD MID/UPPER LEVEL
TROUGH WILL CONTINUE TO PRESS AGAINST A RIDGE OFF THE COAST OF
CHILE. THROUGH SATURDAY MORNING THE RIDGE IS TO NEARLY
FLATTEN/COLLAPSE WHILE THE TROUGH WEAKENS. THIS WILL THEN FAVOR AN
INFLOW OF SHORT WAVE ENERGY AND SUBTROPICAL MOISTURE INTO CENTRAL
PORTIONS OF CHILE ON SATURDAY-SUNDAY...WHEN THE ASSOCIATED FRONT
IS TO MAKE LANDFALL. ON THE CENTRAL REGIONS OF CHILE THIS IS TO
THEN TRIGGER LIGHT CONVECTION WITH MAXIMA FORECAST TO PEAK AT
05-10MM.

ENRIQUEZ...DGAC (ECUADOR)
AYALA...DINAC (PARAGUAY)
GALVEZ/DAVISON...WPC (USA)

$$





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