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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1649Z Jun 02, 2020)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1249 PM EDT TUE JUN 02 2020

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

FORECAST DISCUSSION FROM JUNE 02/17UTC: THE WATER VAPOR IMAGERY
SHOWS A CLOSED LOW/SHORT WAVE TROUGH OFF THE SOUTH COAST OF CHILE.
UNDER THE INFLUENCE OF A MID/UPPER LEVEL RIDGE TO THE WEST...THIS
LOW IS FORECAST TO LIFT ALONG THE COAST TO VALPARAISO CHILE EARLY
ON WEDNESDAY MORNING. THE LOW IS TO CONTINUE NORTH...TO BRIEFLY
STALL JUST WEST OF THE ANDES/NEAR LA SERENA EARLY ON THURSDAY
MORNING. EARLY ON FRIDAY MORNING...AS A DEEPENING MID LEVEL TROUGH
BECOMES THE DOMINANT SYNOPTIC FEATURE OVER THE EASTERN
PACIFIC...THE CLOSED LOW IS FORECAST TO JUMP ACROSS THE NORTHERN
ANDES OF CHILE TO THE NORTHWEST PROVINCES IN ARGENTINA. IT IS TO
THEN TRACK TO THE EAST-SOUTHEAST ACROSS NORTHERN ARGENTINA TO
SOUTHERN BRASIL/URUGUAY DURING THE DAY ON FRIDAY. AT 250 HPA...A
POLAR JET MAXIMA ROUNDING THE CLOSED LOW IS TO THEN FAVOR AN UPPER
DIVERGENT PATTERN AS IT STREAMS ACROSS NORTHERN ARGENTINA TO
URUGUAY/SOUTHERN BRASIL. AT LOW LEVELS...A MEANDERING FRONT
STRETCHES ACROSS THE SOUTH ATLANTIC-SAO PAULO-MATO GROSSO DO SUL
IN BRASIL TO CENTRAL BOLIVIA...WHILE THE MID LEVEL TROUGH SUSTAINS
A SECONDARY BOUNDARY OVER CENTRAL ARGENTINA/CENTRAL CHILE. AS THE
MID LEVEL LOW/SHORT WAVE TROUGH SPILLS ACROSS THE NORTHERN ANDES
OF CHILE...IT IS TO INTERACT WITH THE OLD BOUNDARY TO THE
NORTH...FAVORING A FRONTAL WAVE OVER PARAGUAY EARLY ON THURSDAY
MORNING. ON THURSDAY TO FRIDAY...UNDER FAVORABLE JET
DYNAMICS...THE FRONTAL LOW IS FORECAST TO DEEPEN WHILE RAPIDLY
OCCLUDING ACROSS URUGUAY/ENTRE RIOS IN ARGENTINA. OVER THE CENTRAL
ANDES OF CHILE THIS IS TO TRIGGER HEAVY SNOWFALL AMOUNTS...WITH
MAXIMA OF 20-30CM THROUGH WEDNESDAY MORNING...WHILE ALONG THE
CENTRAL COAST OF CHILE IT WILL SUSTAIN LIGHT RAINFALL AMOUNTS WITH
MAXIMA OF 05-10MM. OVER PARAGUAY...THE DEEPENING FRONTAL LOW WILL
SUSTAIN MAXIMA OF 15-30MM LATER ON WEDNESDAY/EARLY ON THURSDAY
MORNING. ON THURSDAY THIS INCREASES TO 35-70MM WHILE BUILDING EAST
ACROSS MISIONES IN ARGENTINA TO SOUTHERN BRASIL. MOISTURE WRAPPING
AROUND THE OCCLUDING LOW IS TO THEN FAVOR AN ECHO TRAINING PATTERN
ACROSS URUGUAY-ENTRE RIOS IN ARGENTINA ON FRIDAY-SATURDAY...WITH
MAXIMA OF 30-60MM.

UPSTREAM OVER THE EASTERN PACIFIC...A MID/UPPER LEVEL RIDGE IS TO
INITIALLY EXTEND SOUTH BETWEEN 80W-100W. EARLY IN THE CYCLE...A
POLAR TROUGH IS TO STREAM JUST SOUTH OF THIS RIDGE...WITH AXIS TO
FOCUS ITS SHORT WAVE ENERGY AND SUBTROPICAL MOISTURE ACROSS THE
SOUTHERN REGIONS OF CHILE. THROUGH THURSDAY...THE INFLOW OF SHORT
WAVE ENERGY WILL RESULT IN THE EROSION OF THE MID LEVEL RIDGE
PATTERN. THIS SETS THE STAGE FOR A HIGH AMPLITUDE/LONG WAVE TROUGH
TO AMPLIFY ACROSS THE EASTERN PACIFIC ALONG 85W/90W TO 20S LATER
ON FRIDAY. THE HIGH AMPLITUDE TROUGH IS TO ALSO FOCUS SHORT WAVE
ENERGY AND SUBTROPICAL MOISTURE ACROSS THE SOUTHERN REGIONS OF
CHILE. AT LOW LEVELS...A BROAD POLAR TROUGH IS TO MOVE TO THE
SOUTHEAST PACIFIC/BELLINGSHAUSEN SEA ON WEDNESDAY...WITH AXIS TO
QUICKLY EXPAND ACROSS THE SOUTHERN CONE WHILE MOVING EAST ACROSS
THE ANTARCTIC PENINSULA TO THE WEDDELL SEA. STRONG BOUNDARY LAYER
WINDS ACCOMPANY THE DEEPENING SURFACE TROUGH...WITH WINDS ACROSS
SOUTHERN CHILE/TIERRA DEL FUEGO-PATAGONIA IN ARGENTINA TO PEAK AT
35-50KT. THE STRONG WINDS WILL ENHANCE LOW LEVEL MOISTURE
TRANSPORT AND CONVERGENCE ON THE SOUTHERN REGIONS OF CHILE...WHILE
ADIABATICALLY ASCENDING ACROSS THE SOUTHERN ANDES. THE 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...A BROAD CELL OF THE
SUBTROPICAL RIDGE ENVELOPS CONTINENTAL AREA TO THE NORTH OF
20S...WITH AXIS ANCHORING ON A CLOSED HIGH OVER NORTHEAST STATES
OF BRASIL. THROUGH THURSDAY MORNING THE CLOSED HIGH IS TO MEANDER
TO THE WEST-SOUTHWEST TO MATO GROSSO IN CENTRAL BRASIL...AND
LATTER IN THE CYCLE IT WILL DRIFT WEST TO NORTHERN BOLIVIA. AS THE
RIDGE HOLDS TO THE NORTH...A SUBTROPICAL JET IS TO BOUND THE
SOUTHERN FRINGES OF THIS RIDGE DURING THE NEXT 84-96 HRS. THE
RIDGE ALOFT IS TO ALSO 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.
MOST ACTIVE OVER PARA/AMAPA IN BRASIL IS EXPECTED EARLY IN THE
CYCLE WITH MAXIMA OF 20-30MM...WHILE OVER AMAZONAS TO THE
WEST/SOUTHERN COLOMBIA-NORTHERN JUNGLE OF PERU IT INCREASES FROM
20-30MM EARLY IN THE CYCLE TO 30-60MM ON THURSDAY.
THIS...HOWEVER...WILL BE SHORT LASTING...WITH ACTIVITY FORECAST TO
GRADUALLY EBB DURING THE WEEKEND.

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