651
FXSA20 KWBC 212029
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
328 PM EST THU NOV 21 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 21 NOV 2024 AT 2030 UTC:

THE NORTHERN HALF OF THE SOUTH AMERICAN CONTINENT WILL OBSERVE
SHOWERS AND THUNDERSTORMS EACH DAY. PARTICULARLY OVER THE AMAZON
BASIN INTO PORTIONS OF BOLIVIA. EASTERN BRAZIL AS WELL AS ITS
SOUTHEASTERN COAST WILL HAVE AN ENHANCED CHANCE OF SHOWERS AND
THUNDERSTORMS OVER THE NEXT FEW DAYS. THE REASONS DIFFER...BUT
MOST OF SOUTH AMERICA WILL BE ACTIVE WITH SHOWERS AND
THUNDERSTORMS. THE DRIER AREAS WILL BE THE NORTHERN HALF OF CHILE
AND MOST OF ARGENTINA. THERE IS A CHANCE OF DAILY SHOWERS AND
THUNDERSTORMS OVER CENTRAL ARGENTINA...NEAR LA PAMPA...HOWEVER.
SOUTHERN CHILE HAS A GOOD CHANCE OF SHOWERS IN THE LOWER
ELEVATIONS WITH MOUNTAIN SNOW POSSIBLE...ESPECIALLY FOR THE REST
OF TODAY INTO SATURDAY.

THE BOLIVIAN HIGH IS PREVAILING...WHICH IS HELPING THE DEVELOPMENT
OF CONVECTION ACROSS THE AMAZON...AS WELL AS CONTRIBUTING TO A
TIGHT PRESSURE GRADIENT...THEREFORE STRONG UPPER LEVEL WINDS
CENTRAL CHILE AND ARGENTINA. THE UPPER LEVEL WINDS ACROSS THE
AMAZON BASIN WILL NOT BE AS STRONG AS THOSE ACROSS CENTRAL CHILE
AND ARGENTINA...BUT IT WILL BE ENOUGH TO VENTILATE PULSE
THUNDERSTORMS THAT WILL DEVELOP DUE TO THE INTERACTION OF DIURNAL
HEATING...SFC TROUGHS...AND THE AVAILABLE MOISTURE. THE SHOWERS
AND THUNDERSTORMS THAT ARE EXPECTED EACH DAY ACROSS THE AREA...ARE
EXPECTED TO CAUSE RAINFALL GENERALLY IN THE 15-25MM RANGE...WITH
ISOLATED HIGHER AMOUNTS REACHING 40-45MM. THERE IS ALSO A
TROPOSPHERIC KELVIN WAVE OVER THE REGION...WHICH MAY CONTRIBUTE TO
THE RAINFALL ACROSS THE NORTHWEST AMAZON BASIN. THIS IS WHY
NORTHWEST BRASIL AND PORTIONS OF EASTERN PERU HAS A RAINFALL
FORECAST MAXING OUT AT 20-45MM. ECUADOR ALSO HAS UP TO
45MM...WHILE ELSEWHERE IN PERU HAS UP TO 35MM IN THE FORECAST.
THERE ARE SOME AREAS IN BOLIVIA THAT ARE FORECAST TO OBSERVE
FORECAST MAX VALUES REACHING 40-80MM FOR THE REST OF TODAY INTO
FRIDAY MORNING...THEN UP TO 50MM ON FRIDAY INTO SATURDAY
MORNING...WITH LOWER AMOUNTS ON SATURDAY INTO SUNDAY. CURRENT
SATELLITE IMAGERY INDICATES DEEPER CONVECTION OCCURRING OVER
EASTERN BOLIVIA...CLOSE TO THE BORDER WITH PARAGUAY...AND THIS IS
EXPECTED TO CONTINUE ACROSS THE NORTHERN AND EASTERN SECTIONS OF
BOLIVIA INTO FRIDAY MORNING.

A FRONTAL BOUNDARY...EXTENDING ACROSS THE ATLANTIC INTO EASTERN
BRAZIL WILL PROVIDE CONSTANT MOISTURE TO THE EASTERN COAST OF
BRAZIL FROM SAO PAULO TO ESPIRITO SANTO. THE HIGHER THAN NORMAL
MOISTURE WILL PREVAIL OVER THE NEXT FEW DAYS...WHICH WILL
CONTRIBUTE TO AMOUNTS OF RAIN UP TO 50MM TODAY. EVEN HIGHER
AMOUNTS OF RAIN ARE EXPECTED FROM FRIDAY INTO EARLY SUNDAY FOR THE
AFOREMENTIONED AREAS IN BRAZIL...WITH RAINFALL AMOUNTS MAXING OUT
NEAR 70MM. THE ABOVE NORMAL MOISTURE WILL PREVAIL...BUT MID AND
UPPER TROUGHS WILL START TO MOVE NORTH...AND PROVIDE STRONGER
WINDS ALOFT...INCREASING INSTABILITY.

EVEN THOUGH ARGENTINA IS EXPECTED TO BE GENERALLY DRY...A
DEVELOPING COLD FRONT OVER THE CENTRAL PORTIONS WILL INTERACT WITH
LOCALLY HIGHER THAN NORMAL MOISTURE AND A DIFFLUENT PATTERN IN THE
MID AND UPPER LEVELS. THE MODEL GUIDANCE IS NOT VERY AGGRESSIVE
WITH THE TOTAL RAINFALL AMOUNTS...WITH MAX TOTALS GENERALLY AROUND
15-35MM EACH DAY INTO THE WEEKEND...BUT THE STRONGER WINDS ALOFT
WITH THE COLD MID LEVEL TEMPERATURES ARE FAVORABLE FOR A MARGINAL
TO SLIGHT RISK OF STRONG THUNDERSTORMS EACH DAY INTO SUNDAY
MORNING.

THE NORTHERN HALF OF CHILE IS FORECAST TO REMAIN MAINLY DRY FOR
THE NEXT FEW DAYS...BUT A STRONG LOW PRESSURE IN TEH PACIFIC WILL
BRING ABOVE NORMAL MOISTURE TO THE SOUTHERN HALF OF THE COUNTRY
TODAY AND FRIDAY INTO SATURDAY. THERE ARE ALSO STRONG MID AND
UPPER LEVEL WINDS...WHICH WILL AFFECT THE AREA UNTIL SATURDAY.
THIS WILL CAUSE SHOWERS AND THUNDERSTORMS OVER THE SOUTHERN
PORTION OF CHILE...WITH MOUNTAIN SNOW. RAINFALL MAX VALUES TO 45MM
ARE FORECAST EACH DAY UNTIL SATURDAY MORNING...THEN UP TO 25MM ON
SATURDAY INTO SUNDAY AS DRIER AIR MOVES IN AND THE WINDS ALOFT
WEAKEN.


ALAMO...(WPC)
$$