Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXSA20 KWBC 291541
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1140 AM EDT MON AUG 29 2016

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

MODEL DISCUSSION (VALID FROM AUG 29 AT 0000 UTC): AMPLIFYING POLAR
TROUGH MOVES ACROSS THE EASTERN PACIFIC INTO THE SOUTHERN CONE OF
SOUTH AMERICA EARLY ON TUESDAY MORNING. THE MID/UPPER LEVEL TROUGH
IS TO THEN MEANDER EAST INTO THE WESTERN ATLANTIC...WHERE IT IS TO
THEN DOMINATE THE FLOW THROUGH THE END OF THE WEEK. AS IT PUSHES
ACROSS SOUTHERN CHILE INTO PATAGONIA IN ARGENTINA THE DEEP MID
LEVEL TROUGH WILL SUSTAIN HEIGHTS FALLS IN EXCESS OF 150GPM. AT
LOW LEVELS...THE ASSOCIATED SURFACE TROUGH WILL EXTEND FROM THE
ANTARCTIC PENINSULA TO SOUTHERN CHILE/PATAGONIA IN
ARGENTINA...WHILE ANCHORING ON A DEEP 958-960 HPA LOW OVER THE
DRAKE PASSAGE. POLAR FRONTS WILL REVOLVE AROUND THIS AXIS...WHILE
A BUILDING POLAR RIDGE TO THE WEST SUSTAINS A COLD ADVECTIVE
PATTERN ACROSS THE BELLINGSHAUSEN SEA TO TIERRA DEL FUEGO/SOUTHERN
CHILE. THIS IS TO RESULT IN STRONG BOUNDARY LAYER WINDS DURING THE
NEXT THREE DAYS. THIS WILL DRIVE SUCCESSIVE FRONTS NORTH ACROSS
THE SOUTHERN CONE INTO CENTRAL PROVINCES IN ARGENTINA/RIO DE LA
PLATA BASIN. EARLY IN THE PERIOD THE DEEP TROUGH WILL SUSTAIN THE
ADVECTION OF SUBTROPICAL MOISTURE ACROSS THE EASTERN PACIFIC INTO
SOUTHERN CHILE. UNDER FAVORABLE JET DYNAMICS THIS IS TO TRIGGER
MODERATE CONVECTION ACROSS CHILE BETWEEN TEMUCO AND ISLA DE
CHILOE...WITH MAXIMA IN THIS AREA TO PEAK AT 20-40MM. ON WEDNESDAY
IT DECREASES TO 10-15MM IN ISOLATED TO SCATTERED CONVECTION. OVER
TIERRA DEL FUEGO INITIALLY EXPECTING SCATTERED RAIN SHOWERS TO
TRIGGER RAINFALL AMOUNTS OF 05-10MM. ON TUESDAY THE COLUMN WILL BE
COLD ENOUGH TO SUSTAIN TRANSITION TO MOSTLY SOLID
PRECIPITATION...TO RESULT IN SNOWFALL AMOUNTS OF 05-10CM. ON
WEDNESDAY THIS IS TO ONLY FAVOR TRACE AMOUNTS IN MIXED
PRECIPITATION...WITH RAIN/SNOW SHOWERS TO PESTER THE AREA FROM
TIME-TO-TIME.

ALSO AT 500 HPA...A SHORT WAVE TROUGH MEANDERS EAST ACROSS
NORTHERN CHILE INTO NORTHWEST ARGENTINA LATER THIS EVENING. AS THE
POLAR TROUGH DEEPENS TO THE SOUTH...THE SHORT WAVE TROUGH WILL
THEN ACCELERATE ACROSS NORTHERN ARGENTINA-PARAGUAY TO SOUTHERN
BRASIL LATER ON TUESDAY. THROUGH THURSDAY IT MIGRATES FARTHER EAST
INTO THE SOUTH ATLANTIC WHERE IT MERGES WITH THE BROAD POLAR
TROUGH TO THE SOUTH. AT LOW LEVELS THIS SUSTAINS AN OCCLUDING LOW
OVER MESOPOTAMIA IN ARGENTINA/SOUTHERN BRASIL LATER TODAY. THE
DEEPENING LOW WILL FAVOR A SOUTHERLY JET ACROSS CHACO ARGENTINO TO
BOLIVIA. THE SOUTHERLY SURGE WILL THEN DRIVE THE ASSOCIATED FRONT
NORTH ACROSS MATO GROSSO DO SUL-RONDONIA IN BRASIL TO NORTHERN
BOLIVIA. THROUGH TUESDAY EVENING THE FRONT IS TO CONTINUE NORTH
ACROSS SAO PAULO IN BRASIL...TRAILING ACROSS MATO GROSSO TO ACRE
IN BRASIL/SOUTHERN JUNGLE OF PERU. EARLY ON WEDNESDAY...AS UPPER
LEVEL SUPPORT WEAKENS...THE FRONT IS TO STALL OVER SAO
PAULO/SOUTHERN MINAS GERAIS WHILE TRAILING WEST TO SANTA
CRUZ/NORTHERN BOLIVIA. OVER CORRIENTES IN ARGENTINA-SOUTHERN
BRASIL THE OCCLUDING LOW WILL TRIGGER MODERATE CONVECTION WITH
ACCUMULATION OF 25-50MM EXPECTED THROUGH MIDMORNING ON TUESDAY. ON
TUESDAY...AS THE FRONT MOVES TO SAO PAULO...IT IS TO SUSTAIN
RAINFALL MAXIMA OF 20-40MM. HIGHER AMOUNTS...HOWEVER...ARE
EXPECTED TO THE NORTH AS THE FRONT SURGES ACROSS BOLIVIA. IN THIS
AREA EXPECTING MAXIMA OF 35-70MM THROUGH TUESDAY MORNING. AS THE
CONVECTION SPREADS NORTH ACROSS ACRE/SOUTHERN AMAZONAS IN BRASIL
AND THE PERUVIAN JUNGLE THIS WILL DECREASE TO 20-35MM DURING THE
DAY ON TUESDAY...WHILE HIGHER AMOUNTS ARE TO BUILD ACROSS NORTHERN
AMAZONAS-NORTHERN JUNGLE OF PERU AND SOUTHERN COLOMBIA ON TUESDAY
TO WEDNESDAY...WITH MAXIMA IN THIS AREA EXPECTED TO PEAK AT
25-50MM. THROUGH THURSDAY THIS WILL DECREASE TO 15-20MM.

BUILDING CONVECTION ACROSS BRASIL WILL RELEASE LATENT HEAT INTO
THE ATMOSPHERE. IN RESPONSE TO THE AVAILABLE ENERGY THE MODELS
SHOW AN UPPER LEVEL RIDGE SLOWLY BUILDING ACROSS BRASIL THROUGH
WEDNESDAY AFTERNOON. THE BUILDING RIDGE IS TO CONTINUE VENTING
DIURNAL CONVECTION ACROSS NORTHWEST SOUTH AMERICA/PERUVIAN JUNGLE
THROUGH THE END OF THE WEEK. AS THE RIDGE HOLDS...SHORT WAVE
TROUGHS WILL PROPAGATE ACROSS THE EASTERN TROPICAL PACIFIC. THESE
ARE TO ENTER THE CONTINENT BETWEEN NORTHERN CHILE-CENTRAL PERU. AS
SUCCESSIVE PERTURBATIONS MAKE LANDFALL TO THE NORTH...THESE ARE TO
FAVOR AN UPPER DIVERGENT PATTERN ACROSS THE HIGH JUNGLE IN
SOUTHERN PERU. STARTING ON WEDNESDAY THIS IS TO THEN FAVOR
MODERATE CONVECTION WITH ACCUMULATION OF 15-20MM. THROUGH FRIDAY
ACTIVITY WILL GRADUALLY SPREAD TO THE SOUTHEAST ACROSS BOLIVIA
WHERE IT IS TO INCREASE TO 20-35MM.

OSORIO...DMC (CHILE)
CASTILLO...UCR (COSTA RICA)
ALVA...SENAMHI (PERU)
DAVISON...WPC (USA)
$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.