494
FXSA20 KWBC 282046
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
346 PM EST TUE JAN 28 2025
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 28 JAN 2025 AT 2045 UTC:
SOUTH AMERICA IS UNDER THE CONVERGENT PHASE OF THE MADDEN-JULIAN
OSCILLATION TODAY...THOUGH POSSIBLY DECREASING BY THE END OF THE
MONTH. THERE IS ALSO THE POTENTIAL OF AN ATMOSPHERIC KELVIN WAVE
ENTERING THE REGION BY THE LATTER PART OF THE WORKWEEK...WHICH
COULD ENHANCE CONVECTION.
AN UPPER-LEVEL TROUGH IS CURRENTLY MOVING THROUGH ARGENTINA AND IS
EXPECTED TO PROPAGATE INTO THE ATLANTIC BY FRIDAY...WHERE IT WILL
DEEPEN AND DEVELOP INTO A LOW-PRESSURE SYSTEM. AS THIS TROUGH
INTERACTS WITH THE BOLIVIAN HIGH...LOCALLY STRONGER WINDS ARE
ANTICIPATED ACROSS NORTHERN ARGENTINA INTO SOUTHERN BRAZIL.
ADDITIONALLY...AN UPPER LOW OVER NORTHWESTERN BRAZIL WILL INTERACT
WITH THE BOLIVIAN HIGH...LEADING TO LOCALLY ENHANCED WINDS ACROSS
WESTERN BRAZIL AND NORTHERN BOLIVIA TODAY THROUGH THURSDAY
MORNING. OVER SOUTHERN SOUTH AMERICA...AN UPPER-LEVEL JET REMAINS
ACTIVE ACROSS AUSTRAL SOUTH AMERICA...AIDING IN DYNAMIC SUPPORT
FOR PRECIPITATION EVENTS IN THE REGION.
AT MID-LEVELS...A SHORTWAVE TROUGH WILL TRACK THROUGH NORTHERN
ARGENTINA INTO SOUTHERN BRAZIL AND URUGUAY TODAY INTO
WEDNESDAY...GENERATING ENHANCED VORTICITY IN THE AREA. THIS WILL
ELEVATE THE LIKELIHOOD OF CONVECTION...PARTICULARLY IN REGIONS
WITH FAVORABLE MOISTURE CONVERGENCE. STRONG ZONAL WESTERLY WINDS
ARE EXPECTED ACROSS AUSTRAL SOUTH AMERICA...SUPPORTING ENHANCED
MOISTURE ADVECTION AND PRECIPITATION OVER THE REGION. OVER
NORTHERN SOUTH AMERICA...A BROAD MID-LEVEL HIGH-PRESSURE SYSTEM IS
CENTERED OVER EASTERN BRAZIL AND BOLIVIA...STABILIZING MUCH OF THE
REGION. HOWEVER...A WEAK MID-LEVEL TROUGH WITH ENHANCED VORTICITY
IS EXPECTED ACROSS THE NORTHERNMOST CENTRAL SECTIONS OF SOUTH
AMERICA DURING MIDWEEK...POTENTIALLY SUPPORTING LOCALIZED
CONVECTIVE ACTIVITY.
A SERIES OF LOW-LEVEL TROUGHS WILL DEVELOP ACROSS THE SOUTH
AMERICAN CONTINENT OVER THE NEXT FEW DAYS...ENHANCING MOISTURE
CONVERGENCE IN SEVERAL REGIONS. THE SOUTH AMERICAN LOW-LEVEL JET
(SALLJ) WILL TRANSPORT MOISTURE SOUTHWARD INTO CENTRAL
ARGENTINA...INCREASING THE POTENTIAL FOR PRECIPITATION THROUGH
THURSDAY. MEANWHILE...A FRONTAL BOUNDARY WITH STRONG LOW-LEVEL
WINDS WILL MOVE INTO AUSTRAL CHILE TODAY...PERSISTING THROUGH
THURSDAY. THIS BOUNDARY WILL DRIVE AN ATMOSPHERIC RIVER INTO THE
REGION...BRINGING APPROXIMATELY 30MM OF PRECIPITABLE WATER...WHICH
IS 2 STANDARD DEVIATIONS ABOVE NORMAL. AS A RESULT...EXCESSIVE
RAINFALL IS EXPECTED ACROSS PORTIONS OF AUSTRAL CHILE THROUGH
MIDWEEK INTO THURSDAY. IN TERMS OF RAINFALL AMOUNTS AND ACTIVE
WEATHER...THERE IS A RISK OF MCS DEVELOPMENT AND SEVERE WEATHER
ACROSS NORTHERN ARGENTINA TODAY...WITH 40-80MM OF RAINFALL
POSSIBLE. PORTIONS OF PARAGUAY MAY ALSO EXPERIENCE SEVERE WEATHER
TODAY...THOUGH EXPECTED RAINFALL TOTALS ARE LOWER...WITH UP TO
35MM FORECASTED. MEANWHILE...THE ATMOSPHERIC RIVER AND FRONTAL
BOUNDARY OVER AUSTRAL CHILE COULD RESULT IN 30-60MM OF RAIN.
LOOKING AHEAD TO WEDNESDAY 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 STRONG MID AND
UPPER-LEVEL WINDS...WILL SIGNIFICANTLY ENHANCE SHOWER ACTIVITY.
AND OUR FORECAST SUGGESTS THE CHANCE FOR SIGNIFICANT RAINFALL
TOTALS...WITH MAXIMA POTENTIALLY REACHING 100MM. BY THURSDAY INTO
FRIDAY...THE RAINFALL PATTERN IS EXPECTED TO BECOME MORE
WIDESPREAD AND LESS CONCENTRATED OVER NORTHERN SOUTH AMERICA. MUCH
OF TROPICAL SOUTH AMERICA MAY EXPERIENCE RAINFALL MAXIMA OF
20-45MM...THOUGH THE MID AND UPPER-LEVEL WINDS ARE NOT EXPECTED TO
BE AS FAVORABLE FOR STRONG CONVECTION. HIGHER-THAN-NORMAL MOISTURE
WILL PERSIST ACROSS THE TROPICAL SOUTH AMERICAN REGION...BUT WITH
THE MID AND UPPER-LEVEL TROUGHS MOVING INTO THE ATLANTIC BY
THEN...THE RISK OF SEVERE WEATHER OVER CENTRAL SOUTH AMERICA WILL
DIMINISH. IN AUSTRAL CHILE...ELEVATED MOISTURE LEVELS ASSOCIATED
WITH THE ATMOSPHERIC RIVER WILL CONTINUE...THOUGH IT WILL BE
SHORTER-LIVED. RAINFALL AMOUNTS FOR THE REGION ARE FORECAST TO MAX
OUT AT AROUND 45MM.
ALAMO...(WPC)
ALAMO...(WPC)
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