SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
206 PM EDT FRI JUL 26 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 26 JUL 2024 AT 1800 UTC:

A WIDE UPPER LEVEL TROUGH EXTENDS OVER THE SOUTHERN CONE OF SOUTH
AMERICA. THE JETS ASSOCIATED WITH THE TROUGH ARE NOT AS STRONG
OVER THE REGION ON FRIDAY. THROUGHOUT THE DAY...THE JETS INTENSIFY
AND THE UPPER TROUGH PROPAGATES OVER THE REGION. TO THE WEST OF
THE TROUGH...A RIDGE IN THE UPPER LEVELS IS ADVANCING AND WILL BE
PROPAGATING EAST OVER THE WEEKEND. IN THE LOWER LEVELS...FRONTAL
PASSAGES ARE EXPECTED FROM THE SOUTH...AND THEY ARE EXPECTED TO
ADVECT COLD AIR ON FRIDAY AND SATURDAY. IN ADDITION...THE AMOUNTS
OF LOW LEVEL MOISTURE ARE EXPECTED TO REMAIN BELOW 15MM OF
PRECIPITABLE WATER. THAT IS UNTIL EARLY MONDAY...WHEN THE NEXT
ATMOSPHERIC RIVER IS EXPECTED TO BE OFFSHORE...TO THE WEST OF
CHILE. IN TERMS OF PRECIPITATION...ON FRIDAY...EXPECT MAXIMA OF
20-40MM WITH THE CHANCE OF THUNDERSTORMS. ON SATURDAY...THE
AMOUNTS ARE EXPECTED TO DECREASE TO 15-25MM. BOTH DAYS ARE
EXPECTED TO SEE MOUNTAIN SNOW IN THE HIGHER ELEVATIONS. SNOW
ACCUMULATIONS ARE EXPECTED IN MAGALLANES WITH SNOWFALL MAXIMA OF
05-10CM. ON SUNDAY...LITTLE TO NO PRECIPITATION IS EXPECTED IN THE
SOUTHERN REGION.

IN THE CENTRAL PORTION OF THE REGION...A WEAK UPPER LEVEL TROUGH
EXTENDS INTO SOUTHERN BOLIVIA AND PARAGUAY...WHILE FRONTOGENESIS
IS EXPECTED OVER THE REGION ON FRIDAY INTO SATURDAY. THE REGION
FROM BOLIVIA INTO NORTH ARGENTINA...AND BRASIL WILL BEGIN TO SEE
AN INCREASE IN PRECIPITABLE WATER OVER THE NEXT SEVERAL
DAYS...WITH A MAXIMA EXPECTED ON SUNDAY. THE UPPER LEVEL
CONDITIONS...WITH THE INCREASE IN MOISTURE WILL FAVOR INSTABILITY
OVER THE REGION. FROM LATE SATURDAY...TO EARLY MONDAY EXPECT
SEVERE WEATHER FROM NORTH ARGENTINA...INTO SOUTH PARAGUAY...SOUTH
BRASIL...AND EXTREME NORTHEAST PORTIONS OF URUGUAY. IN TERMS OF
PRECIPITATION...ON FRIDAY...TRACE AMOUNTS OF PRECIPITATION IS
EXPECTED FROM SOUTHERN PARAGUAY TO SOUTH BRASIL. ON SATURDAY..WITH
THE PASSING OF THE UPPER LEVEL TROUGH...DIVERGENCE ALOFT WILL
FAVOR MARGINAL RISK OF SEVERE WEATHER IN EXTREME NORTH ARGENTINA
AND WEST PARAGUAY...WITH MAXIMA OF 15-20MM. SIMILAR AMOUNTS ARE
EXPECTED IN SOUTHEAST RIO GRANDE DO SUL. ON SUNDAY...THE AREA IS
EXPECTING A MODERATE RISK OF SEVERE WEATHER FROM PARAGUAY...NORTH
ARGENTINA...TO SOUTHERN BRASIL. FROM FORMOSA-ARGENTINA...TO
SOUTHWEST PARAGUAY EXPECT MAXIMA OF 20-45MM. SOUTHEAST RIO GRANDE
DO SUL CAN EXPECT MAXIMA OF 20-35MM. ELSEWHERE IN ARGENTINA AND
SOUTHERN BRASIL EXPECT MAXIMA OF 15-25MM.

OF NOTE FOR THE FOLLOWING WEEK...THE MADDEN JULIAN OSCILLATION MAY
BECOME FAVORABLE FOR WETTER CONDITIONS FOR THE LATER PART OF NEXT
WEEK. THE CFS MODEL IS ESTIMATING A DIVERGENT PHASE APPROACHING
WESTERN SOUTH AMERICA BY MID NEXT WEEK...AND A KELVIN WAVE MAY BE
PROPAGATING INTO THE REGION AS WELL. THE EXACT TIMING OF THE
ARRIVAL TO THE CONTINENT IS STILL UNCERTAIN...HOWEVER...CONDITIONS
MAY SHIFT BY MID WEEK AND INTO THE LATER PART OF NEXT WEEK...TO
WETTER AND WITH HEAVIER PRECIPITATIONS IF THE SYNOPTIC CONDITIONS
ARE IN PLACE. WE ARE MONITORING THE SITUATION AS MODEL GUIDANCE
GAINS CONFIDENCE.

ACOSTA...(WPC)