157
FXSA20 KWBC 182028
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
328 PM EST WED DEC 18 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 18 DEC 2024 AT 2015 UTC:
UPPER LEVELS...A STRONG UPPER LEVEL TROUGH IS NOW EAST OF BRASIL
AND INTO THE WESTERN ATLANTIC. ACROSS THE TROPICAL SOUTH
AMERICA...THE BOLIVIAN HIGH PRESSURE CONTINUES TO MAINTAIN MOSTLY
LIGHT WINDS ALOFT BUT STILL CONTRIBUTES TO STRONG WINDS ACROSS THE
NORTHERN PORTIONS OF CHILE AND ARGENTINA. THERE IS A SHORTWAVE
TROUGH PASSING THROUGH CENTRAL ARGENTINA TODAY...WHICH WILL MOVE
OFFSHORE LATE THURSDAY NIGHT. ANOTHER UPPER LEVEL TROUGH HAS MOVED
OVER THE SOUTHERN PORTIONS OF THE CONTINENT AND NOW HAS ITS AXIS
ACROSS THE SOUTHWESTERN ATLANTIC. THERE IS ALSO STRONG WINDS ALOFT
MOVING INTO THE SOUTHERN THIRD OF THE CONTINENT...WITH WINDS
EXCEEDING 100 KNOTS OVER SOUTHERN CHILE AND THE MOUNTAINOUS AREAS
OF SOUTHERN ARGENTINA.
MID LEVELS...A SIMILAR PATTERN EXISTS AT THE MID LEVELS...WITH THE
TROUGH AXIS HAVING MOVED EASTWARD ACROSS CENTRAL SOUTH AMERICA.
STRONG VORTICITY IS PRESENT OVER CENTRAL ARGENTINA AS A SHORTWAVE
MID LEVEL TROUGH PASSES THROUGH...WHICH WILL SUPPORT CONVECTIVE
DEVELOPMENT IN THESE AREAS. THE BROADER MID LEVEL TROUGH OVER
SOUTHERN SOUTH AMERICA IS ALSO ADVANCING EASTWARD...MAINTAINING
RELATIVELY STRONG WINDS IN THESE REGIONS. MID LEVELS ACROSS
TROPICAL SOUTH AMERICA REMAIN UNDER LIGHTER WINDS AND A WEAK HIGH
PRESSURE INFLUENCE.
SEVERAL TROUGHS AND AREAS OF CONVERGENCE IN THE LOWER LEVELS WILL
CONTINUE TO PROMOTE CONVECTION OVER PORTIONS OF NORTH-CENTRAL
ARGENTINA INTO PARAGUAY INTO THURSDAY...THEN OVER SOUTHERN BRASIL
ON FRIDAY INTO SATURDAY. AVAILABLE MOISTURE REMAINS HIGHER THAN
NORMAL ACROSS MOST OF THE CONTINENT TODAY EXCEPT FOR COASTAL
PERU...BOLIVIA...NORTHERN CHILE...AND PORTIONS OF SOUTHERN BRASIL
AND URUGUAY. MOISTURE WILL DECREASE GRADUALLY OVER THE NEXT COUPLE
OF DAYS ACROSS THE SOUTHERN HALF OF THE CONTINENT.
HOWEVER...SOUTH-CENTRAL CHILE WILL EXPERIENCE A BRIEF PERIOD OF
MUCH HIGHER THAN NORMAL MOISTURE ON THURSDAY...CONTRIBUTING TO AN
INCREASE IN PRECIPITATION.
COMBINED WITH THE STRONG MID AND UPPER LEVEL WINDS...THERE IS A
SLIGHT RISK OF SEVERE WEATHER OVER ISOLATED AREAS OF NORTH CENTRAL
ARGENTINA INTO SOUTHERN BRASIL. THESE AREAS OF HEAVIER
PRECIPITATION ARE EXPECTED TO OBSERVE DAILY MAX RAINFALL AMOUNTS
BETWEEN 30 TO 80MM. OTHER AREAS WILL RECEIVE LESSER AMOUNTS OF
RAIN...WITH THE TROPICAL REGION OF SOUTH AMERICA OBSERVING TYPICAL
DIURNAL CONVECTION WITH MAX VALUES GENERALLY RANGING FROM
15-35MM...THOUGH ISOLATED HIGHER AMOUNTS ARE POSSIBLE.
ALAMO...(WPC)
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