352
FXSA20 KWBC 291942
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM EST WED JAN 29 2025
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 29 JAN 2025 AT 1940 UTC:
AN UPPER-LEVEL TROUGH IS CURRENTLY MOVING THROUGH NORTHEAST
ARGENTINA INTO URUGUAY...AND IS EXPECTED TO PROPAGATE INTO THE
ATLANTIC BY FRIDAY...WHERE IT WILL DEEPEN AND DEVELOP INTO A
LOW-PRESSURE SYSTEM. THAT SAID...AN ASSOCIATED TROUGH WILL REMAIN
IN PLACE OVER THE AREA INTO THE WEEKEND...WITH ITS AXIS NEAR
SOUTHEASTERN BRASIL..URUGUAY...AND PARAGUAY. THIS TROUGH WILL
CONTINUE TO INTERACT WITH THE BOLIVIAN HIGH...CAUSING LOCALLY
STRONGER WINDS ACROSS NORTHERN ARGENTINA INTO SOUTHERN BRAZIL
TODAY. THE BOLIVIAN HIGH WILL MOVE WEST AND WILL BE POSITIONED
OVER THE PACIFIC...WEST OF CHILE BY THIS WEEKEND...HOWEVER. OVER
AUSTRAL SOUTH AMERICA...AN UPPER-LEVEL JET REMAINS ACTIVE...AIDING
IN DYNAMIC SUPPORT FOR PRECIPITATION IN THE REGION...ESPECIALLY
THIS AFTERNOON AND EVENING AS A SHORTWAVE TROUGH MOVES INTO
AUSTRAL SOUTH AMERICA. IN THE MID-LEVELS...A SHORTWAVE TROUGH WILL
TRACK THROUGH NORTHERN ARGENTINA INTO SOUTHERN BRAZIL AND URUGUAY
TODAY...ENHANCING THE CHANCES OF CONVECTION ACROSS PARAGUAY.
STRONG ZONAL WESTERLY WINDS ARE EXPECTED ACROSS AUSTRAL SOUTH
AMERICA TODAY INTO THURSDAY...SUPPORTING ENHANCED MOISTURE
ADVECTION AND PRECIPITATION OVER THE REGION. HOWEVER...A MID LEVEL
TROUGH WILL MOVE IN LATE THURSDAY INTO FRIDAY...THOUGH THE WINDS
WILL REMAIN STRONG...REACHING OVER 75KT. OVER NORTHERN SOUTH
AMERICA...A MID-LEVEL HIGH-PRESSURE SYSTEM IS CENTERED OVER
EASTERN BRAZIL AND BOLIVIA TODAY...STABILIZING MUCH OF THE REGION.
HOWEVER...A MID LEVEL TROUGH WILL PERSIST OVER PARAGUAY AND
SOUTHEASTERN BRASIL LATE IN THE WEEK INTO THE WEEKEND...ENHANCING
THE CHANCES OF SHOWERS AND THUNDERSTORMS.
A SERIES OF LOW-LEVEL TROUGHS WILL BE PRESENT ACROSS THE SOUTH
AMERICAN CONTINENT OVER THE NEXT FEW DAYS...ENHANCING MOISTURE
CONVERGENCE IN SEVERAL REGIONS. THERE IS SOME INDICATION BY THE
MODEL GUIDANCE THAT THE LOWER LEVELS MAY DEVELOP A PATTERN
MARGINALLY CONSISTENT WITH THE DEVELOPMENT OF A SACZ LATE THIS
WEEKEND...THOUGH THIS IS BEYOND THE FORECAST PERIOD AND THERE IS
CONSIDERABLE UNCERTAINTY STILL...IT IS SOMETHING TO
WATCH...HOWEVER. A COLD FRONT WITH STRONG LOW-LEVEL WINDS WILL
MOVE INTO AUSTRAL CHILE TONIGHT INTO THURSDAY. THIS BOUNDARY WILL
CONTINUE TO DRIVE AN ATMOSPHERIC RIVER INTO THE REGION...BRINGING
PRECIPITABLE WATER THAT IS ABOUT 2 STANDARD DEVIATIONS HIGHER THAN
NORMAL FOR THE AREA. THEREFORE...EXCESSIVE RAINFALL IS EXPECTED
ACROSS PORTIONS OF AUSTRAL CHILE TODAY INTO THURSDAY. THE FRONTAL
BOUNDARY IS EXPECTED TO PUSH THROUGH AND IT MAY BE TO THE EAST OF
THE CHILE MOUNTAINS BY THURSDAY NIGHT...BUT THE ATMOSPHERIC RIVER
WILL CONTINUE TO AFFECT PORTIONS OF CHILE AS IT SLOWLY MOVED
NORTH...ALBEIT WITH LESS MOISTURE WITH EACH PASSING DAY.
IN TERMS OF RAINFALL AMOUNTS AND ACTIVE WEATHER OVER THE NEXT FEW
DAYS...WITH THE EXCEPTION OF A COLD FRONT CAUSING SOME RAINFALL
OVER A SMALL AREA OF SOUTHERN ARGENTINA ON THURSDAY AND ANOTHER
SMALL AREA OVER BUENOS AIRES ON FRIDAY...ARGENTINA IS EXPECTED TO
REMAIN FAIRLY DRY...AS WELL AS THE NORTHERN HALF OF CHILE. THAT
SAID...TROPICAL SOUTH AMERICA AND AUSTRAL SOUTH AMERICA WILL HAVE
SIGNIFICANT RAINFALL IN SOME AREAS...ESPECIALLY AS ABOVE NORMAL
MOISTURE IS EXPECTED TO PERSIST OVER THE AFOREMENTIONED AREAS.
THOUGH DRIER AIR WILL BE MOVING IN FROM THE NORTH ACROSS THE
GUIANAS BY SATURDAY.
TODAY INTO EARLY THURSDAY...A SURFACE TROUGH...COMBINED WITH THE
INTERACTION OF AN UPPER-LEVEL AND MID-LEVEL SHORTWAVE
TROUGH...WILL INCREASE THE RISK OF MCS DEVELOPMENT IN PARAGUAY.
ADDITIONALLY...AN AREA OF EASTERN BRAZIL MAY SEE 30-60MM OF
RAINFALL DURING THIS PERIOD. ACROSS AUSTRAL CHILE...THE
ATMOSPHERIC RIVER...IN CONJUNCTION WITH THE STRONG MID AND
UPPER-LEVEL WINDS...WILL SIGNIFICANTLY ENHANCE SHOWER
ACTIVITY...POSSIBLY CAUSING AS MUCH AS 50-100MM OF RAIN ACROSS
AUSTRAL CHILE. ACROSS TROPICAL SOUTH AMERICA...MIST OF THE AREA IS
EXPECTED TO OBSERVE RAINFALL MAXIMA OF AROUND 20-45MM...WITH THE
EXCEPTION OF THE AFOREMENTIONED AREAS IN PARAGUAY AND EASTERN
BRASIL...AS WELL AS SOME AREAS OF NORTHERN BRASIL ALONG A LOW
LEVEL TROUGH...WHICH IS FORECAST UP TO 50MM OF RAIN TODAY. FOR
THURSDAY INTO FRIDAY...SOME AREAS OF EASTERN BRASIL AS WELL AS A
SMALL SECTION NEAR MARANHAO AND TOCANTINS IN BRASIL MAY HAVE
STRONG STORMS...BUT OTHER AREAS ACROSS NORTHERN SOUTH AMERICA WILL
BE OBSERVING DIURNAL THUNDERSTORMS...WITH MAX TOTALS GENERALLY
BETWEEN 20-45MM. A SIMILAR RAINFALL PATTERN CAN BE EXPECTED ON
FRIDAY INTO SATURDAY ACROSS TROPICAL SOUTH AMERICA...WITH THE
HIGHEST AMOUNTS OF RAIN EXPECTED ACROSS SAO PAULO ALONG A LOW
LEVEL TROUGH...WITH TOTALS MAXING OUT AT 30-60MM...AND A SMALL
AREA NEAR MARANHAO WITH MAXIMA NEAR 35-70MM. OTHERWISE...OTHER
AREAS WILL HAVE DIURNAL CONVECTION WITH MAXIMA IN THE ORDER OF
20-45MM.
ALAMO...(WPC)
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