SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
351 PM EST TUE DEC 03 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 03 DEC 2024 AT 1930 UTC: A
BROAD POLAR MID-UPPER TROUGH CONTINUES EXTENDING OVER THE WEDDELL
SEA AND SOUTHWEST ATLANTIC. AS THIS TROUGH IS FORECAST TO MOVE
LITTLE THROUGH THE FORECAST CYCLE...IT IS EXPECTED TO STEER
SHORTER WAVES NORTHWARD ALONG THE SOUTH COAST OF CHILE. A TROUGH
CURRENTLY EXTENDING SOUTH OF 40S AND NEAR 87-90W IS FORECAST TO
MEANDER NORTHWARD SLOWLY TO EXTEND ACROSS PENINSULA VANDEZ INTO
CONCEPCION BY FRIDAY AFTERNOON. THE SLOW MOVEMENT OF THIS TROUGH
WILL ALLOW FOR CYCLOGENESIS TO DEVELOP IN PATAGONIA ON WEDNESDAY.
DEVELOPING EASTERLY FLOW IN THE LOWER TROPOSPHERE WILL INTERACT
WITH UPPER TROUGH DYNAMICS TO DEVELOP PERIODS OF MODERATE
PRECIPITATION BY WEDNESDAY THROUGH EARLY THURSDAY EXPECT MAXIMA OF
15-20MM IN THE CENTRLA PATAGONIA OF ARGENTINA WHILE WEST OF THE
ANDES ONSHORE FLOW WILL FAVOR MAXIMA OF 15-25MM. ON THURSDAY
THROUGH EARLY FRIDAY EXPECT HEAVY PRECIPITATION DEVELOPING NORTH
OF COMODORO RIVADAVIA INTO THE VIEDMA REGION...WHERE EXPECT
10-15MM/DAY AND MAXIMA OF 20-45MM...WHILE IN INTERIOR PORTIONS OF
THE PATAGONIA EXPECT 05-10MM/DAY AND ISOLATED MAXIMA OF 15-25MM.

THE PERSISTENT BOLIVIAN HIGH IN CENTRAL PORTIONS OF THE CONTINENT
IS FAVORING A BRANCH OF THE SUBTROPICAL JET ACROSS NORTH-CENTRAL
ARGENTINA NEAR 30-32N. AS THE AFOREMENTIONED UPPER TROUGH
APPROACHES THE REGION ON THURSDAY TO THE SOUTH OF THIS
JET...EXPECT MID-TROPOSPHERIC AIR TO BE SUFFICIENTLY COOL TO FAVOR
ENHANCED INSTABILITY AND THE POTENTIAL FOR SEVERE WEATHER.
ALTHOUGH LARGE VALUES OF PRECIPITABLE WATER ARE EXPECTED TO REMAIN
MOSTLY IN CENTRLA BRASIL...AVAILABLE MOISTURE WILL BE SUFFICIENT
TO TRIGGER MAXIMA OF 20-35MM IN URUGUAY/RIO GRANDE DO SUL AND
NORTHEAST ARGENTINA WITH A MODERATE RISK FOR SEVERE WEATHER. IN
CENTRAL PORTIONS OF ARGENTINA EXPECT MAXIMA OF 15-20MM ALSO WITH A
MODERATE RISK FOR SEVERE WEATHER.

IN TROPICAL PORTIONS OF THE CONTINENT...EXPECT A CONTINUED
ACTIVATION OF CONVECTION AS A POTENT CAVADO DO NORDESTE LOW
INTERACTS WITH THE BOLIVIAN HIGH TO THE WEST. THIS...IN
COMBINATION WITH A GRADUAL DECREASE OF LARGE SCALE UPPER
CONVERGENCE ASSOCIATED WITH THE MJO...WILL YIELD TO A CONTINUED
ACTIVATION OF DIURNAL CONVECTION IN THE AMAZON BASIN AND PERIODS
WITH MODERATE ACCUMULATIONS. OF INTEREST IS A SURFACE FRONT
PROPAGATING ACROSS SOUTHEAST BRASIL ON TUESDAY. THIS WILL FAVOR
MAXIMA OF 75-125MM ALONG RIO DE JANEIRO AND NORTHERNH SAO
PAULO...WHILE IN AREAS INLAND SUCH AS MINAS GERAIS AND GOIAS
EXPECT MAXIMA OF 40-80MM AND A RISK FOR MCS FORMATION. ALSO IN
ASSOCIATION WITH THE WESTERN TIER OF THE FRONT...FORECAST TO
WEAKEN ACROSS CENTRAL AND NORTHERN BOLIVIA ON TUESDAY...EXPECT
MAXIMA OF 30-60MM. ON WEDNESDAY EXPECT MAXIMA OF 30-60MM FROM RIO
DE JANEIRO INTO EASTERN PARA/WESTERN MARANHAO. AREAS OF HEAVY
RAINFALL ARE FORECAST TO RELOCATE WESTWARD TO CENTER IN
RONDONIA...MATO GROSSO AND SOUTHWEST PARA/AMAZONAS ON THURSDAY.

GALVEZ/TINOCO...(WPC)