SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1243 PM EDT TUE APR 26 2022

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

FORECAST DISCUSSION FROM APR 26/17 UTC: CONSISTENT WITH PREVIOUS
FORECASTS...UNDER THE INFLUENCE OF A LONG WAVE RIDGE TO THE
WEST...A HIGH AMPLITUDE MID/UPPER LEVEL TROUGH IS FORECAST TO
AMPLIFY FROM THE ANTARCTIC PENINSULA TO MID SECTIONS OF SOUTH
AMERICA LATER TODAY. IN STRONG AGREEMENT...THE GLOBAL MODELS THEN
FORECAST THE HIGH AMPLITUDE TROUGH TO SLOWLY RELOCATE ACROSS THE
CONTINENT TO THE WESTERN ATLANTIC THROUGH THE EARLY MORNING HOURS
ON THURSDAY. THIS WILL THEN EVOLVE INTO A BROAD TROUGH WHILE
SLOWLY PULLING TO THE EAST-SOUTHEAST. MEANWHILE...AS IT ENTERS THE
CONTINENT...A SUBTROPICAL AND A NORTHERN POLAR JET MAXIMA ARE
FORECAST TO ROUND THE BASE OF THE LONG WAVE AXIS. AS THEY STREAM
ACROSS CHILE TO ARGENTINA THE JETS ARE FORECAST TO COUPLE OFF THE
COAST OF BUENOS AIRES...FAVORING A BROAD AREA OF UPPER DIVERGENCE.
UNDER THE INFLUENCE OF THE HIGH AMPLITUDE TROUGH AND FAVORABLE
UPPER LEVEL JET DYNAMICS...THE ENVIRONMENTAL CONDITIONS REMAIN
FAVORABLE FOR EXPLOSIVE CYCLOGENESIS (FORMATION OF A
METEOROLOGICAL BOMB)...WITH A 996 HPA LOW SOUTH OF BUENOS AIRES
PROVINCE LATER THIS EVENING...TO STRENGTHENT TO A 984 HPA LOW BY
DAYBREAK ON WEDNESDAY. THROUGH THE END OF THE DAY IT IS TO
MAINTAIN THE INTENSE RATE OF INTENSIFICATION...DEEPENING TO A 956
HPA LOW AS IT NEARS 50S 50W. THE SURFACE LOW REACHES MAXIMUM
INTENSITY OF 936 HPA AS IT NEARS THE SOUTH GEORGIA ISLAND EARLY ON
THURSDAY MORNING. AT LOW LEVELS THIS WILL LIKELY FAVOR HURRICANE
INTENSITY WINDS AS IT PROPAGATES TO THE SOUTHEAST...WHILE AT UPPER
LEVELS IT WOULD LEAD TO EXTREME AIRCRAFT TURBULENCE.

MEANWHILE...THIS WILL SUSTAIN A BROAD TROUGH ACROSS THE SOUTHERN
CONE...WITH FRONTAL LOWS TO REVOLVE AROUND THIS AXIS. A
PARTICULARLY STRONG LOW ENTERS SOUTHERN CHILE LATER THIS EVENING.
THIS WILL ACCELERATE ACROSS NORTHERN PATAGONIA TO THE WESTERN
ATLANTIC AS THE AFOREMENTIONED METEOROLOGICAL BOMB INTENSIFES
BETWEEN THE MALVINAS/FALKLAND AND THE SOUTH GEORGIA ISLANDS. OVER
THE CONTINENT THESE COMBINE IN SUPPORT OF A PROGRESSIVE FRONT THAT
ADVANCES ACROSS CENTRAL TO NORTHERN ARGENTINA/SOUTHERN BRASIL
LATER ON WEDNESDAY. DRIVEN BY A POLAR RIDGE TO THE SOUTH AND A
SOUTHERLY LOW LEVEL JET...THIS THEN SURGES ACROSS PARAGUAY TO
BOLIVIA ON THURSDAY...WHERE IT IS EXPECTED TO STALL THROUGH THE
END OF THE WEEK. OVER CHILE BETWEEN CONCEPCION AND ISLA DE CHILOE
TO THE SOUTH THIS WILL SUSTAIN MODERATE COASTAL CONVECTION WITH
ACCUMULATION OF 20-45MM THROUGH EARLY WEDNESDAY MORNING...WHILE
ACROSS THE CENTRAL AND SOUTHERN ANDES EXPECTING SNOWFALL AMOUNTS
OF NEARLY A METER PER DAY THROUGH THURSDAY MORNING. OVER THE RIO
DE LA PLATA BASIN/URUGUAY THIS WILL TRIGGER HEAVY SEVERE
CONVECTION...WITH ACCUMULATION OF 35-70MM. ON WEDNESDAY THIS
INCREASES TO 75-125MM WHILE BUILDING NORTH ACROSS URUGUAY TO
SOUTHERN BRASIL/CORRIENTES IN ARGENTINA. MODERATE TO HEAVY
CONVECTION WILL THEN PERSIST ACROSS PARA/RIO GRANDE DO SUL IN
SOUTHERN BRASIL AS WELL AS MISIONES IN ARGENTINA THROUGH THE END
OF THE WEEK. ACROSS CENTRAL BOLIVIA THE MOST INTENSE IS EXPECTED
ON THURSDAY...WITH MAXIMA OF 30-60MM. THIS WEAKENS AS IT SPREADS
NORTH ALONG THE SOUTHERN TO CENTRAL JUNGLE OF PERU...WITH MAXIMA
OF 20-35MM...BUT LATER IN THE WEEK COMBINES INTO A HEAVY RAINFALL
PRODUCING MCS BETWEEN THE NORTHERN JUNGLE OF PERU AND ECUADOR.

AS THE AFOREMENTIONED LONG WAVE TROUGH LIFTS ACROSS THE SOUTHERN
CONE...IT WILL PRESS AGAINST A BROAD CELL OF THE SUBTROPICAL RIDGE
TO THE NORTH...WITH THE LATTER EXTENDING WEST-TO-EAST BETWEEN
24S-08S...WHILE A CELL OF THE SUBEQUATORIAL RIDGE TO THE NORTH
DOMINATES THE FLOW ACROSS NORTHERN SOUTH AMERICA. THE DUAL
BARRELED RIDGE PATTERN WILL RESULT IN A BROAD AREA OF UPPER
DIVERGENCE ACROSS EQUATORIAL SOUTH AMERICA. THIS WILL VENT
CONVECTIVE DEVELOPMENT ACROSS NORTHERN BRASIL-THE
GUIANAS/VENEZUEAL TO COLOMBIA-NORTHERN PERU AND ECUADOR. IN THIS
AREA EXPECTING RAINFALL AMOUNTS OF 15-25MM/DAY...WITH MAXIMA
INCREASING TO 25-50MM AS ENHANCED BY PERTURBATIONS IN THE LOW/MID
LEVEL EASTERLIES. OTHER CONVECTION IS EXPECTED ALONG THE NORTHEAST
COAST OF BRASIL BETWEEN ESPIRITO SANTO AND EASTERN BAHIA DUE TO
TRADE WINDS CONVERGENCE.

DAVISON...WPC (USA)