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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1720Z Jun 01, 2020)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
120 PM EDT MON JUN 01 2020

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

FORECAST DISCUSSION FROM JUNE 01/17UTC: A MID/UPPER LEVEL SHORT
WAVE TROUGH ON THE SOUTHERN STREAM LIFTS ALONG THE SOUTH COAST OF
CHILE EARLY IN THE FORECAST CYCLE. AS THE MID LEVEL TROUGH REACHES
CENTRAL LATER ON TUESDAY...IT IS TO EVOLVE INTO A CLOSED LOW. AS
IT MEANDERS OFF THE COAST...THE LOW/SHORT WAVE TROUGH IS TO SLOWLY
SHEAR SHORT WAVE ENERGY EAST ACROSS THE CENTRAL ANDES INTO THE
CENTRAL PROVINCES IN ARGENTINA. ON FRIDAY THE MID LEVEL TROUGH
WEAKENS ENOUGH THAT IT COULD SPILL ACROSS THE ANDES TO NORTHERN
ARGENTINA. UNDER FAVORABLE JET DYNAMICS IT IS TO BECOME BETTER
ORGANIZED...WITH AXIS TO CENTER ON A CLOSED LOW OVER URUGUAY/RIO
GRANDE DO SUL IN SOUTHERN BRASIL. AT LOW LEVELS...A MEANDERING
FRONT STRETCHES ACROSS SAO PAULO-MATO GROSSO DO SUL IN BRASIL TO
CENTRAL BOLIVIA EARLY IN THE CYCLE...WHILE THE MID LEVEL TROUGH IS
TO SUSTAIN A PROGRESSIVE FRONT THAT SURGES ACROSS PATAGONIA IN
ARGENTINA/SOUTHERN REGIONS OF CHILE. THE LATTER ADVANCES ACROSS
CENTRAL ARGENTINA ON TUESDAY-WEDNESDAY...WHILE THE OLD BOUNDARY TO
THE NORTH STARTS TO RETROGRESS ACROSS PARAGUAY TO NORTHERN
ARGENTINA. AS THEY INTERACT...A DEEPENING FRONTAL WAVE FORMS OVER
CORRIENTES IN ARGENTINA LATER ON WEDNESDAY...FORECAST TO GRADUALLY
DEEPEN WHILE OCCLUDING OVER URUGUAY/RIO GRANDE DO SUL LATER IN THE
WEEK. THIS WILL THEN DRIVE THE FRONT NORTH ACROSS THE SOUTHERN
STATES OF BRASIL INTO TROPICAL SOUTH AMERICA. THIS SYSTEM HAS THE
MAKINGS OF A HEAVY RAINFALL PRODUCER. OVER SOUTHERN CHILE IT WILL
SUSTAIN MODERATE TO HEAVY CONVECTION EARLY IN THE CYCLE...WITH
MAXIMA OF 20-30MM. ON THE CENTRAL ANDES...AS ENHANCED BY THE MID
LEVEL VORTEX...THIS WILL TRIGGER HEAVY SNOWFALL AMOUNTS...WITH
MAXIMA OF 20-30CM. ON THURSDAY-FRIDAY...AS THE FRONTAL WAVE
DEEPENS/OCCLUDES...IT WILL FAVOR AN MCS OVER PARAGUAY-SOUTHERN
BRASIL/MISIONES IN ARGENTINA...WITH RAINFALL AMOUNTS OF
25-50MM/DAY. OVER URUGUAY...PEAK IN CONVECTION IS EXPECTED ON
FRIDAY...WHEN CONDITIONS APPEAR FAVORABLE FOR AN ECHO TRAINING
EVENT...TO SUSTAIN MAXIMA OF 30-60MM.

A HIGHLY AMPLIFIED MID/UPPER LEVEL TROUGH IS TO SLOWLY
FOLLOW...WITH AXIS TO AMPLIFY FROM THE BELLINGSHAUSEN SEA TO THE
ARCHIPELAGO DE JUAN FERNANDEZ EARLY ON FRIDAY MORNING. THE LONG
WAVE TROUGH IS TO THEN FOCUS SUBTROPICAL MOISTURE AND SHORT WAVE
ENERGY ACROSS THE SOUTHERN REGIONS OF CHILE...WHERE IT IS TO
SUSTAIN ORGANIZED CONVECTION. AT LOW LEVELS...THIS WILL SUSTAIN A
BROAD TROUGH ENVELOPING THE BELLINGSHAUSEN SEA/SOUTHEAST PACIFIC
LATER ON WEDNESDAY...WITH AXIS TO RAPIDLY AMPLIFY ACROSS THE
SOUTHERN CONE/LATER IN THE WEEK. THIS WILL BE ACCOMPANIED BY
STRONG BOUNDARY LAYER WINDS...PEAKING AT 35-50KT DURING THE LATTER
PART OF THE WEEK...ENHANCING LOW LEVEL MOISTURE CONVERGENCE AND
ADIABATIC ASCENT ACROSS SOUTHERN CHILE. MOST ACTIVE CONVECTION
WITH THIS FEATURE IS EXPECTED BETWEEN PUERTO MONTT AND ISLA DE
CHILOE IN SOUTHERN CHILE...WITH MAXIMA OF 15-30MM EXPECTED ON
WEDNESDAY-THURSDAY...INCREASING TO 20-40MM ON THURSDAY-FRIDAY.
HEAVY CONVECTION IS TO THEN PERSIST THROUGH SATURDAY
MORNING...WITH STORM TOTAL AMOUNTS NEARING 100MM BY THE END OF THE
PERIOD.

NORTH OVER THE CONTINENT...AT 200 HPA...BROAD CELL OF THE
SUBTROPICAL RIDGE ENVELOPS CONTINENTAL AREA TO THE NORTH OF 20S.
THIS PATTERN IS TO HOLD DURING THE NEXT FIVE-TO-SIX DAYS. AS THE
RIDGE HOLDS TO THE NORTH...A SUBTROPICAL JET IS TO BOUND THE
SOUTHERN FRINGES OF THIS RIDGE. THE RIDGE ALOFT IS TO FAVOR A
DIVERGENT PATTERN OVER EQUATORIAL SOUTH AMERICA. THIS WILL VENT
DEEP CONVECTION IN ASSOCIATION WITH TROPICAL WAVES STREAMING ALONG
THE ITCZ/NEAR EQUATORIAL TROUGH..WITH ONE ENTERING PARA/AMAPA IN
BRASIL TO SUSTAIN MODERATE RAINFALL AMOUNTS WITH MAXIMA OF
20-30MM/DAY OVER THE NEXT COUPLE OF DAYS. AS IT MOVES ACROSS
RORAIMA TO AMAZONAS TO THE WEST LATER IN THE WEEK IT DECREASES TO
15-20MM. ANOTHER WAVE STREAMING ACROSS AMAZONAS IN BRASIL WILL
SUSTAIN SCATTERED CONVECTION...WITH MAXIMA OF 20-35MM EARLY IN THE
CYCLE. AS IT PULLS INTO SOUTHERN COLOMBIA/NORTHERN PERU TO EASTERN
ECUADOR ON WEDNESDAY-THURSDAY THIS INCREASES TO MAXIMA OF 30-60MM.

DAVISON...WPC (USA)
GALVEZ...WPC (USA)