415
FXSA20 KWBC 262003
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
302 PM EST TUE NOV 26 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 26 NOV 2024 AT 1900 UTC:
THE MADDEN-JULIAN OSCILLATION IS FORECAST TO REMAIN CONVERGENT FOR
THE REST OF THE WEEK AND INTO THE WEEKEND. THIS COULD LIMIT THE
AREAS OF HEAVIEST PRECIPITATION FOR THE NEXT SEVERAL DAYS. AT THIS
TIME...SECTORS OF NORTHERN ARGENTINA INTO URUGUAY AND SOUTHERN
PARAGUAY HAVE THE BEST CHANCE FOR SIGNIFICANT RAIN OVER THE NEXT 3
DAYS. HOWEVER...ISOLATED AREAS OF CENTRAL BOLIVIA COULD ALSO
OBSERVE ISOLATED BUT SIGNIFICANT RAINFALL...MAINLY DUE TO THE
INTERACTION OF THE AVAILABLE DEEP MOISTURE WITH THE DIURNAL
HEATING AND THE LOCAL OROGRAPHIC EFFECTS.
AN UPPER TROUGH AND ASSOCIATED LOW JUST WEST OF THE COAST OF
SOUTHERN CHILE WILL MOVE EAST VERY SLOWLY AS IT WEAKENS. THAT
BEING SAID...THIS TROUGH IS ALSO REFLECTED IN THE MID LEVELS...AND
IT HAS A VORTICITY MAXIMA ASSOCIATED WITH IT...WHICH WILL MOVE
THROUGH CHILE AND ARGENTINA OVER THE NEXT FEW DAYS...CONTRIBUTING
TO THE ENHANCED CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE AREA.
THE UPPER LEVEL WINDS WILL BE STRONG ENOUGH ACROSS CHILE AND
ARGENTINA TO CONTRIBUTE IN THE THUNDERSTORM DEVELOPMENT OVER THE
AREA...ESPECIALLY WHEN CONSIDERING THE COLD MID-LEVEL TEMPERATURES
AND THE LOW-LEVEL MOISTURE ADVECTION FROM THE NORTHWEST. THE
RAINFALL FORECAST FOR THE REST OF TODAY INTO WEDNESDAY MORNING
ACROSS NORTHEASTERN ARGENTINA INTO SOUTHERN BRAZIL AND
NORTHWESTERN URUGUAY...WHERE THERE IS ALSO A LOW LEVEL TROUGH AND
UPPER LEVEL DIFFLUENCE...COULD HAVE RAINFALL MAXIMA NEAR 35-70MM
WITH A SLIGHT RISK OF SEVERE WEATHER. A BIT FURTHER WEST INTO
NORTHWESTERN ARGENTINA THE FORECAST RAIN IS A BIT LESS...WITH MAX
TOTALS BEING FORECAST AROUND 20-40MM. FURTHER SOUTH INTO CENTRAL
ARGENTINA AND EASTERN URUGUAY...THERE IS ANOTHER LOW LEVEL TROUGH
BUT THE AMOUNT OF MOISTURE AND AND UPPER LEVEL DYNAMICS WILL BE
LESS CONDUCIVE FOR VERY HIGH AMOUNTS OF RAIN...THEREFORE MAX
TOTALS BETWEEN 15 AND 30MM ARE FORECAST...THOUGH THERE IS ALSO A
MARGINAL RISK OF SEVERE WEATHER OVER EASTERN URUGUAY. THE STRONG
MID AND UPPER LEVEL WINDS INTO CHILE WILL CAUSE ENHANCED
INSTABILITY IN THE AREA...AND FOR THAT REASON THERE IS A CHANCE OF
THUNDERSTORMS OVER THE LOS LAGOS AND LOS RIOS REGION...BUT THE
RAINFALL IS FORECAST TO MAX OUT AT AROUND 15 TO 20MM.
ACROSS THE NORTHERN HALF OF THE CONTINENT...MOST OF THE RAINFALL
EXPECTED EACH DAY WOULD BE HEAVILY INFLUENCED BUY THE DIURNAL
HEATING AND LOCAL EFFECTS. SOME AREAS OF ENHANCED CONVECTION COULD
BE IN AREAS WHERE LOW LEVEL TROUGHS ARE PRESENT...AS IS THE CASE
NOW...AS SUGGESTED BY THE LATEST SATELLITE IMAGERY...WHICH IS
INDICATING A LINE OF CONVECTION THAT HAS DEVELOPED FROM
GUYANA...SOUTH TO BOLIVIA. THAT SAID...OVERALL...MANY AREAS OF
BRAZIL...PERU...AND BOLIVIA ARE OBSERVING THE DEVELOPING OF
CONVECTION AND ARE SLOWLY MOVING WITH THE LOW LEVEL WINDS. THE
DEVELOPING SHOWERS AND THUNDERSTORMS ARE EXPECTED TO CONTINUE INTO
THE EVENING...BUT DECREASE BY WEDNESDAY MORNING. A SIMILAR PATTERN
COULD BE EXPECTED FROM WEDNESDAY INTO THURSDAY...THEN ALSO FROM
THURSDAY INTO FRIDAY...BUT WITH LESS OVERALL RAINFALL COVERAGE
EACH DAY AS DRIER AIR STARTS TO MOVE IN FROM THE NORTHEAST INTO
THE NORTHEASTERN PART OF SOUTH AMERICA.
A STATIONARY FRONT EXTENDS FROM THE SOUTH ATLANTIC INTO NORTHEAST
BRASIL AND IT IS FORECAST FOR IT TO REMAIN IN PLACE THROUGH EARLY
THURSDAY...WEAKENING SLIGHTLY EACH DAY AND REMAINING AS A TROUGH
BY THURSDAY EVENING. AN UPPER TROUGH THAT HAS BEEN ENHANCING
CONVECTION WITH THIS SYSTEM IS GRADUALLY WEAKENING...WHICH WILL
YIELD TO A DECREASE IN AMOUNTS FROM MAXIMA OF 20-35MM TODAY INTO
WEDNESDAY MORNING...TO A MAXIMA OF 15-25MM FOR WEDNESDAY INTO
THURSDAY...AND NO SIGNIFICANT RAIN IS EXPECTED ON THURSDAY INTO
FRIDAY...NOT ONLY BECAUSE OF THE WEAKENING FRONT INTO A
TROUGH...BUT ALSO DUE TO THE INTRUSION OF THE AFOREMENTIONED DRY
AIR INTO NORTHEASTERN SOUTH AMERICA.
ALAMO...(WPC)
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