218
FXSA20 KWBC 222059
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
359 PM EST FRI NOV 22 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 22 NOV 2024 AT 2100 UTC:

THE NORTHERN HALF OF THE SOUTH AMERICAN CONTINENT IS STILL
EXPECTED TO OBSERVE SHOWERS AND THUNDERSTORMS EACH DAY. ESPECIALLY
ACROSS THE AMAZON BASIN AND THE NORTHERN PORTIONS OF BOLIVIA.
EASTERN BRAZIL...ESPECIALLY FROM SAO PAULO TO ESPIRITO SANTO WILL
HAVE AN ENHANCED CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE NEXT
FEW DAYS AS A FRONTAL BOUNDARY EXTENDS FROM THE ATLANTIC INTO THE
EASTERN COAST OF BRAZIL. ELSEWHERE IN SOUTH AMERICA...THE NORTHERN
HALF OF CHILE AND MOST OF ARGENTINA WILL BE DRIER THAN THE
NORTHERN HALF OF THE CONTINENT. THAT BEING SAID...THERE IS A
CHANCE OF DAILY SHOWERS AND THUNDERSTORMS OVER CENTRAL
ARGENTINA...WITH SOME OF THE THUNDERSTORMS WITH A CHANCE OF BEING
SEVERE. CENTRAL TO SOUTHERN CHILE ALSO HAS A GOOD CHANCE OF
SHOWERS AND ISOLATED THUNDERSTORMS THROUGH THE WEEKEND. MOUNTAIN
SNOW IS POSSIBLE TODAY INTO EARLY SATURDAY.

THE BOLIVIAN HIGH IS STILL PREVAILING...WHICH CONTINUES TO PROMOTE
STRONG UPPER LEVEL WINDS FURTHER SOUTH OVER CHILE AND ARGENTINA.
THE UPPER LEVEL WINDS ACROSS CENTRAL ARGENTINA AND CHILE WILL BE
RELATIVELY STRONG...WITH WINDS MAXING OUT AT AROUND 100KT ON
SATURDAY...INCREASING ON SUNDAY AND MONDAY TO AROUND 125-145KT.
THE UPPER LEVEL WINDS OVER THE AMAZON BASIN WILL BE RELATIVELY
WEAK...BUT DIURNAL CONVECTION WILL DEVELOP OVER THE AREA AS
DIURNAL HEATING INTERACTS WITH SFC TROUGHS...AND THE AVAILABLE
MOISTURE. THE THUNDERSTORMS THAT ARE EXPECTED EACH DAY ACROSS THE
AMAZON BASIN ARE EXPECTED TO PRODUCE RAINFALL AMOUNTS GENERALLY IN
THE 15-25MM RANGE...WITH ISOLATED HIGHER AMOUNTS REACHING 40-45MM.
THE MODEL GUIDANCE IS VERY BULLISH WITH RAINFALL AMOUNTS OVER
SOUTHERN BOLIVIA...PERHAPS DUE TO HIGHER THAN NORMAL MOISTURE OVER
THE AREA...BUT THE RAINFALL SOLUTIONS ARE OVERESTIMATING THE
OBSERVED VALUES...FOR THAT REASON WE WENT LOWER THAN THE MODELS IN
THE RAINFALL FORECAST AMOUNTS OVER THE BOLIVIAN PLATEAU...WITH
TOTALS MAXING OUT AT AROUND 15-25MM FOR THE MOST PART...THOUGH
NORTHERN BOLIVIA IS FORECAST UP TO 45MM. CURRENT SATELLITE IMAGERY
INDICATES DECENT CONVECTION OCCURRING OVER MUCH OF THE NORTHERN
HALF OF SOUTH AMERICA...WITH THE DEEPEST CONVECTION OCCURRING OVER
SOUTHERN BRAZIL INTO EASTERN BOLIVIA...CLOSE TO PARAGUAY. BASED ON
THE LATEST GUIDANCE...THIS CONVECTION WILL PERSIST OVER THE NEXT
SEVERAL HOURS BUT WILL GRADUALLY DECREASE IN THE OVERNIGHT HOURS.

THE AFOREMENTIONED FRONTAL BOUNDARY...WHICH IS EXTENDING ACROSS
THE ATLANTIC INTO EASTERN BRAZIL IS STILL EXPECTED TO PROVIDE
CONSTANT MOISTURE TO PORTIONS OF THE EASTERN COAST OF
BRAZIL...FROM SAO PAULO TO ESPIRITO SANTO. THE HIGHER THAN NORMAL
MOISTURE WILL PREVAIL THROUGH THE WEEKEND INTO MONDAY...WHICH WILL
CONTRIBUTE TO AMOUNTS OF RAIN UP TO 70MM TODAY. EVEN HIGHER
AMOUNTS OF RAIN ARE EXPECTED FROM SATURDAY INTO EARLY
SUNDAY...WITH MAX TOTALS AS HIGH AS 100MM...THEN UP TO 60MM ON
SUNDAY INTO MONDAY. THESE HIGH AMOUNTS OF RAIN WILL BE DUE TO THE
COMBINATION OF THE ABOVE NORMAL MOISTURE AND THE MID AND UPPER
TROUGHS THAT WILL MOVE NORTH...AND PROVIDE STRONGER
WINDS...DIVERGENCE AND AN INCREASE IN INSTABILITY.

EVEN THOUGH ARGENTINA IS EXPECTED TO BE GENERALLY DRY...A
DEVELOPING COLD FRONT OVER THE CENTRAL PORTIONS AND THE STRONG MID
AND UPPER LEVEL WINDS...WILL INTERACT WITH LOCALLY HIGHER THAN
NORMAL MOISTURE TO CAUSE SHOWERS AND THUNDERSTORMS OVER CENTRAL
ARGENTINA TODAY AND SATURDAY. THE MAX RAINFALL TOTALS ARE FORECAST
TO BE GENERALLY AROUND 10-25MM TODAY AND SATURDAY...BUT THE
STRONGER WINDS ALOFT WITH THE COLD MID LEVEL TEMPERATURES ARE
FAVORABLE FOR A MARGINAL TO SLIGHT RISK OF STRONG THUNDERSTORMS
EACH DAY. FOR SUNDAY INTO MONDAY...A DIFFLUENT PATTERN IN THE
UPPER LEVELS WILL HELP IN THE DEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ACROSS NORTHEASTERN ARGENTINA...WHERE UP TO 50MM OF
RAIN ARE FORECAST. THIS SYNOPTIC PATTERN MAY CAUSE A MODERATE RISK
OF SEVERE WEATHER ACROSS NORTHEASTERN ARGENTINA INTO SOUTHERN
URUGUAY.

THE NORTHERN HALF OF CHILE IS STILL FORECAST TO REMAIN MAINLY DRY
THROUGH THE WEEKEND...BUT A STRONG LOW PRESSURE IN THE PACIFIC
WILL BRING ABOVE NORMAL MOISTURE TO THE CENTRAL TO SOUTH CENTRAL
PORTIONS OF THE COUNTRY FROM TODAY THROUGH EARLY SUNDAY. THERE ARE
ALSO STRONG MID AND UPPER LEVEL WINDS...WHICH WILL AFFECT THE AREA
THROUGH THE WEEKEND. THIS WILL CAUSE SHOWERS AND THUNDERSTORMS
OVER THE CENTRAL TO SOUTHERN PORTIONS OF CHILE. RAINFALL MAX
VALUES TO 30MM ARE FORECAST EACH DAY UNTIL SUNDAY MORNING...THEN
UP TO 25MM ON SUNDAY INTO MONDAY AS DRIER AIR MOVES IN.


ALAMO...(WPC)
$$