375
FXSA20 KWBC 152042
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
342 PM EST WED JAN 15 2025
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 15 JAN 2025 AT 2030 UTC:
OVER THE NEXT 3 DAYS...BRASIL IS ONCE AGAIN EXPECTED TO RECEIVE
SIGNIFICANT RAIN...ESPECIALLY ACROSS THE EASTERN TO CENTRAL
PORTIONS. TODAY IS EXPECTED TO BE THE RAINIEST DAY ACROSS THE
EASTERN HALF OF BRASIL...FOLLOWED BY CENTRAL BRASIL ON
THURSDAY...THEN FRIDAY INTO SATURDAY WOULD BE A BIT DRIER AS DRY
AIR MOVES IN FROM THE EAST. THAT BEING SAID...THERE IS A SMALL
AREA OF SOUTH CENTRAL BRASIL THAT COULD OBSERVE AS MUCH AS
40-80MM. THE SACZ IS EXPECTED TO DISSIPATE BY THURSDAY...AND THE
AFOREMENTIONED DRIER AIR WILL START TO MOVE INTO EASTERN BRASIL.
IN TERMS OF RAINFALL TOTALS...MANY SECTORS OF EASTERN BRASIL ARE
FORECAST RAINFALL TOTALS MAXING OUT NEAR 35-80MM TODAY. THAT THE
GFS MODEL IS AGAIN A BIT MORE BULLISH THAN THE OTHER MODELS WITH
THE FORECAST RAINFALL AMOUNTS...AND WHILE THE OTHER GLOBAL MODELS
ARE DRIER...WE WENT WITH AN AVERAGE OF THE MODEL OUTPUTS BASED ON
RECENT OBSERVATIONS AND RECENT MODEL PERFORMANCE. FOR THURSDAY
INTO FRIDAY...CENTRAL BRASIL WILL HAVE THE HIGHER AMOUNTS OF
RAIN...MAXING OUT NEAR 30-80MM ALONG A TROUGH THAT EXTENDS FROM
PARA TO MINAS GERAIS. RAINFALL AMOUNTS ARE EXPECTED TO DIMINISH
FROM FRIDAY INTO SATURDAY...WITH MOST AREAS OF BRASIL RECEIVING
MAX VALUES BETWEEN 20-35MM...EXCEPT ONE AREA OF MATO GROSSO THAT
HAS 30-60MM IN THE FORECAST.
THE MOUNTAINOUS REGION FROM PERU INTO BOLIVIA AND NORTHERN CHILE
WILL HAVE SHOWERS AND THUNDERSTORMS EACH DAY BUT THE RAINFALL
TOTALS WILL BE GENERALLY UP TO 25MM. THAT SAID...THE MODEL
GUIDANCE IS STILL SUGGESTING AN AREA OF SOUTHERN PERU THAT COULD
OBSERVE AS MUCH AS 30-60MM ON THURSDAY INTO FRIDAY. SOUTHERN CHILE
WILL ALSO OBSERVE SHOWER ACTIVITY EACH DAY WITH THE RAINFALL
TOTALS GENERALLY PEAKING AT AROUND 15-25MM WITH MOUNTAIN SNOW
EXPECTED ON FRIDAY INTO SATURDAY. HOWEVER...A PATCH OF MOISTURE IS
FORECAST TO MOVE INTO SOUTHERN...OR AUSTRAL...CHILE LATE THURSDAY
INTO EARLY FRIDAY...CAUSING THE PRECIPITATION AMOUNTS TO BE UP TO
35MM.
IN THE UPPER LEVELS...A HIGH PRESSURE IS STILL EXPECTED TO DEVELOP
NEAR MINAS GERAIS BY THURSDAY MORNING. A LOW PRESSURE IS
APPROACHING NORTHEASTERN BRASIL TODAY. A LOW PRESSURE OVER
SOUTHEASTERN BRASIL...AS WELL AS A WEAK LOW PRESSURE OVER NORTHERN
ARGENTINA...ARE CAUSING RELATIVELY STRONG WINDS ALOFT OVER
SOUTHERN BRASIL INTO SOUTHERN PARAGUAY...WITH MAX SPEEDS NEAR 70
KNOTS. WESTERLY WINDS ARE FORECAST OVER SOUTHERN SOUTH
AMERICA...WITH WINDS WEAKENING BUT STILL NEAR 100 KT ON
THURSDAY...THOUGH WEAKENING EVEN FURTHER ON FRIDAY INTO SATURDAY
AS AN UPPER TROUGH MOVES IN.
IN THE MID LEVELS...A BROAD MID LEVEL TROUGH MOVED INTO SOUTHERN
SOUTH AMERICA TODAY AND IS EXPECTED TO MOVE INTO THE ATLANTIC BY
THIS EVENING. ZONAL WESTERLY WINDS ARE EXPECTED ACROSS AUSTRAL
SOUTH AMERICA ON FRIDAY...BUT A MID LEVEL TROUGH WILL MOVE THROUGH
LATE FRIDAY INTO SATURDAY. THE MODEL GUIDANCE CONTINUES TO
INDICATE AREAS OF HIGHER VORTICITY OVER TROPICAL SOUTH
AMERICA...AS WELL AS SOUTHEASTERN BRASIL.
IN THE LOW LEVELS...THE WINDS WILL BE FROM THE NORTH TO NORTHWEST
OVER NORTH CENTRAL TO NORTHWESTERN SOUTH AMERICA...WHICH IS
BRINGING DRY AIR TO THE AREA. EASTERLY WINDS WILL MOVE INTO
EASTERN BRASIL...ALSO WITH DRIER AIR MOVING IN. MOST OF THE
MOISTURE IS OVER CENTRAL BRASIL...WHERE THE SACZ IS WEAKENING BUT
A LOW LEVEL LOW PRESSURE IS SLOWLY DEVELOPING. STRONG 850 MB WINDS
ARE AFFECTING AUSTRAL SOUTH AMERICA...BUT EVEN STRONGER WINDS WILL
MOVE INTO THE AREA LATE FRIDAY INTO SATURDAY MORNING...WITH WIND
SPEEDS POSSIBLY REACHING 60 KT AT THE 850 MB LEVEL.
ALAMO...(WPC)
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