145
FXSA20 KWBC 041915
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
215 PM EST WED DEC 04 2024

GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/

SOUTH AMERICAN FORECAST BULLETIN FOR 04 DEC 2024 AT 1810 UTC: A
MID-UPPER TROUGH IS PROPAGATING ACROSS SOUTHERN SOUTH AMERICA FROM
SOUTHWEST TO NORTHEAST...AS IT IS BEING STEERED BY A LARGER
MID-UPPER POLAR TROUGH LOCATED IN THE SOUTHWEST ATLANTIC. THE
TROUGH IS FORECAST TO PROPAGATE FROM SOUTHERN PATAGONIA...TAITAO
PENINSULA...31S 88W ON WEDNESDAY TO 50S 53W...SOUTHWEST BUENOS
AIRES PROVINCE...MENDOZA BY FRIDAY EVENING. THE SLOW EVOLUTION OF
THE UPPER TROUGH IS DEVELOPING LOW-LEVEL EASTERLY FLOW IN CENTRAL
PATAGONIA...WHICH IS RESULTING IN THE DEVELOPMENT OF DEEP
CONVECTION AND MODERATE PRECIPITATION FOR THE REGION. THROUGH
EARLY THURSDAY EXPECT MAXIMA OF 15-20MM. FROM THURSDAY INTO EARLY
FRIDAY THIS IS EXPECTED TO INCREASE TO 15-20MM/DAY AND MAXIMA OF
25-50MM IN EASTERN RIO NEGRO. THIS DECREASES THEREAFTER. ALSO ON
THURSDAY...AS AVAILABLE LOW-LEVEL MOISTURE RECOVERS IN CENTRAL
ARGENTINA AND THE RIO DE LA PLATA REGION AND A SURFACE FRONT
ORGANIZES...EXPECT THE DEVELOPMENT OF SCATTERED MOIST CONVECTION.
GIVEN LOW TEMPERATURES IN THE MID-TROPOSPHERE...EXPECT SUFFICIENT
INSTABILITY TO STIMULATE THE DEVELOPMENT OF SEVERE CONVECTION. BY
THURSDAY INTO EARLY FRIDAY...EXPECT MAXIMA OF 20-45MM DEVELOPING
FROM ENTRE RIOS INTO CENTRAL AND NORTHERN URUGUAY AND SOUTHERN RIO
GRANDE DO SUL...WITH A MODERATE RISK OF SEVERITY. ACROSS CENTRAL
ARGENTINA FROM CORDOBA INTO MOST OF THE BUENOS AIRES PROVINCE
EXPECT MAXIMA OF 15-20MM/DAY ALSO WITH A MODERATE RISK FOR
SEVERITY. ON FRIDAY INTO EARLY SATURDAY...EXPECT A
REINTENSIFICATION OF THE SALLJ ACROSS BOLIVIA AND PARAGUAY...WHICH
WILL STIMULATE MOISTURE CONVERGENCE IN SOUTHERN
PARAGUAY...NORTHEAST ARGENTINA AND PORTIONS OF SOUTHERN BRASIL.
INTERACTIONS WITH SHORT WAVE MID-UPPER TROUGHS WILL FAVOR PERIODS
OF HEAVY RAINFALL. EXPECT AMOUNTS OF 20-40MM WITH POTENTIAL MAXIMA
OF 75-125MM AND A RISK FOR MCS FORMATION. IN NORTHWEST ARGENTINA
AS WELL AS IN SOUTHERN RIO GRANDE DO SUL EXPECT 05-10MM/DAY AND
MAXIMA OF 15-30MM.

IN TROPICAL SOUTH AMERICA...THE BOLIVIAN HIGH CONTINUES BEING THE
DOMINANT FEATURE WHILE CENTERING OVER WESTERN MATO GROSSO AND
EXTENDING FROM SOUTHEAST BRASIL INTO NORTHWEST BRASIL/NORTHERN
PERU. A CLOSED UPPER LOW (OR VORTICE CICLONIC DE ALTOS NIVELS -
VCAN) CENTERS OVER FAR NORTHEAST BRASIL. THIS IS ENHANCING
SOUTHERLY UPPER FLOW AND VENTILATION IN EASTERN BRASIL. THE VCAN
IS FORECAST TO RETROGRADE TO CENTER OVER SOUTHEAST PARA BY
SATURDAY EVENING...WHICH WILL RESULT IN A GRADUAL WESTWARD
MIGRATION OF THE REGION OF HIGHEST VENTILATION/UPPER DIVERGENCE
BETWEEN THE BOLIVIAN HIGH AND THE VCAN. FURTHERMORE...A GRADUAL
DECREASE IN UPPER CONVERGENCE IN THE LARGE SCALE...IN ASSOCIATION
WITH THE MJO...WILL FAVOR MODERATE RAINFALL DEVELOPING IN PORTIONS
OF THE CENTRAL AND WESTERN AMAZON AS THE FORECAST CYCLE
PROGRESSES. IN TERMS OF THE AREAS WHERE THE HEAVIEST PRECIPITATION
IS EXPECTED...ON WEDNESDAY EXPECT MAXIMA OF 30-60MM FROM SOUTHERN
MARANHAO INTO PARA IN BRASIL...AND MAXIMA OF 20-45MM FROM GOIAS
INTO MINAS GERAIS AND RIO DE JANEIRO. IN NORTHWEST BRASIL/NORTHERN
PERU EXPECT MAXIMA OF 15-30MM. EXPECT SIMILAR AMOUNTS ALONG A
TROUGH LOCATED FROM THE PANTANAL INTO NORTHERN BOLIVIA AND
SOUTHERN PERU. ON THURSDAY...EXPECT THE HEAVIEST PRECIPITATION TO
CLUSTER FROM CENTRAL PARA AND CENTRAL AMAZONAS SOUTH INTO MATO
GROSSO AND RONDONIA...WHERE EXPECT MAXIMA OF 35-70MM. IN SOUTHEAST
BRASIL...EXPECT MAXIMA OF 15-30MM ALONG A SURFACE TROUGH FORECAST
TO EXTEND FROM RIO DE JANEIRO INTO NORTHERN MATO GROSSO DO SUL. ON
FRIDAY EXPECT MAXIMA OF 20-45MM ACROSS MOST OF THE CENTRAL AMAZOBN
FROM NORTHERN PARA INTO AMAZONAS AND RONDONIA. ALSO ON
FRIDAY...ENHANCED VENTILATION AND CYCLONIC VORTICITY ALONG THE
NORTHERLY LOW-LEVEL JET WILL FAVOR MAXIMA OF 40-80MM ALONG THE
CENTRAL AND SOUTHERN AMAZON OF PERU AND NORTHWEST BOLIVIA.

GALVEZ...(WPC)
$$