282
FXSA20 KWBC 241714
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1214 PM EST TUE DEC 24 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 24 DEC 2024 AT 1710 UTC:
MADDEN-JULIAN CONDITIONS ARE BECOMING GRADUALLY MORE FAVORABLE FOR
VENTILATION AND HEAVIER PRECIPITATION IN SOUTH
AMERICA...PARTICULARLY IN TROPICAL PORTIONS OF THE CONTINENT. THIS
WILL FAVOR A GRADUAL INCREASE IN THE COVERAGE AND INTENSITY OF
PRECIPITATING CONVECTION AS THE WEEKEND APPROACHES.
AN AMPLIFIED POSITIVELY TILTED MID-UPPER TROUGH EXTENDS ACROSS THE
BUENOS AIRES PROVINCE INTO SAN JUAN AND LA SERENA ON TUESDAY
MORNING. THE TROUGH IS EXPECTED TO MEANDER EASTWARD INTO
URUGUAY...NORTHERN SANTA FE THROUGH EARLY HOURS OF CHRISTMAS
DAY...ACCOMPANIED BY AN UPPER JET MAXIMA TO ITS NORTH. HEIGHT
FALLS AND THE DIVERGENT EXIT OF THIS JET ARE EXPECTED TO STIMULATE
CYCLOGENESIS OFF THE COAST OF URUGUAY AND RIO GRANDE DO SUL ON
WEDNESDAY. THE DEVELOPING LOW IS FORECAST TO MEANDER SLOWLY
OFFSHORE EXERTING LIMITED IMPACTS IN CONTINENTAL AREAS.
HOWEVER...AN INCREASE IN SURFACE PRESSURES IN INTERIOR PORTIONS OF
NORTH-CENTRAL ARGENTINA WILL CONTINUE TO ENHANCE LOW-LEVEL WINDS
EAST OF THE ANDES...TO FAVOR A RAPID NORTHWARD PROGRESSION OF THE
ASSOCIATED SURFACE FRONT. EXPECT THE FRONT TO EXTEND ACROSS
CENTRAL/NORTHWEST PARAGUAY/SOUTHERN BOLIVIA BY TUESDAY
EVENING...RONDONIA/ACRE/SOUTHERN PERU BY WEDNESDAY EVENING...TO
THEN START DISSIPATING ACROSS SOUTHERN LORETO IN PERU BY THURSDAY
EVENING. THE PRESENCE OF HIGH VALUES OF PRECIPITABLE WATER EAST OF
THE ANDES WILL FAVOR STRONG MOISTURE CONVERGENCE AS 30-50KT
SOUTHERLY WINDS PROPAGATE NORTHWARD. THIS WILL FAVOR PERIODS OF
HEAVY RAINFALL THROUGH THE CYCLE. THROUGH CHRISTMAS MORNING EXPECT
THE HEAVIEST PRECIPITATION TO CLUSTER ON NORTHERN PARAGUAY AND
MOST OF EASTERN BOLIVIA WHERE EXPECT 15-30MM/DAY AND MAXIMA OF
40-80MM WITH A RISK FOR MCS FORMATION AND HEAVY RAINFALL RATES. ON
WEDNESDAY THROUGH THURSDAY MORNING EXPECT 25-50MM/DAY AND MAXIMA
OF 75-150MM IN SOUTHERN PERU WITH A RISK OF MCS FORMATION AND
HEAVY RAINFALL RATES. IN ACRE/RONDONIA/SOUTHERN AMAZONAS-BRASIL
AND NORTHERN BOLIVIA EXPECT 15-20MM/DAY AND MAXIMA OF
25-50MM...WHIE IN MATO GROSSO/SOUTHERN RONDONIA THE DISSIPATING
FRONT WILL FAVOR MAXIMA OF 20-45MM. ON THURSDAY...EXPECT THE
DISSIPATING FRONT TO FAVOR MAXIMA OF 30-60MM IN CENTRAL AND
NORTHERN PERU AND IN AMAZONAS-BRASIL.
IN TROPICAL SOUTH AMERICA AND AT UPPER LEVELS...THE BOLIVIAN HIGH
WILL CONTINUE TO REMAIN AS THE DOMINANT FEATURE WHILE CENTERING
ACROSS EASTERN BOLIVIA MATO GROSSO EARLY IN THE CYCLE...TO EVOLVE
INTO A HIGH OVER NORTHERN BOLIVIA WITH AN ELONGATED RIDGE AXIS
EXTENDING TO MINAS GERAIS AND ESPIRITO SANTO BY THURSDAY/FRIDAY.
NOTE THAT THIS IMPLIES UPPER WESTERLIES IN LATITUDES TO THE SOUTH
OF 18N...WHICH GENERALLY FAVOR DRIER CONDITIONS IN THE SOUTHERN
ALTIPLANO/ANDES OF NORTHERN ARGENTINA AND CHILE AND
PARAGUAY/BOLIVIA. HOWEVER...THE HIGH WILL CONTINUE TO VENTILATE
DEEP CONVECTION ALONG ITS EASTERN AND NORTHEAST QUADRANT...AS IT
INTERACTS WITH A MOISTER ENVIRONMENT AND LOW LEVEL FEATURES SUCH
AS THE SACZ AND NET IN BRASIL. ON TUESDAY...EXPECT A RAPIDLY
DISSIPATING SACZ ACROSS ESPIRITO SANTO...GOIAS...EAST MATO GROSSO.
THIS WILL FAVOR MAXIMA OF 20-45MM IN ESPIRITO SANTO/NORTHEAST
MINAS GERAIS AND MAXIMA OF 20-35MM INLAND. HOWEVER...SURFACE
TROUGH AND THE NET WILL FAVOR STRONG CONVECTION IN
TOCANTINS/SOUTHERN PARA WHERE EXPECT MAXIMA OF 25-50MM. ON
WEDNESDAY...A SURFACE TROUGH IS EXPECTED ACROSS WEST RIO DE
JANEITU/SOUTHWEST MINAS GERAIS. AS THIS FEATURE INTERACTS WITH A
WEAK SHORT WAVE UPPER TROUGH EXPECT STRONG CONVECTION TO DEVELOP
AND FAVOR 15-20MM/DAY AND MAXIMA OF 30-60MM. ON THURSDAY...EXPECT
THE REORGANIZATION OF THE SACZ ONCE AGAIN...THIS TIME IN
ASSOCIATION WITH THE REMNANTS OF THE SURFACE FRONT. BY THURSDAY
EVENING EXPECT THE SACZ TO EXTEND ACROSS NORTHERN SAO
PAULO...WESTERN MATO GROSSO...NORTHERN RONDONIA...WESTERN
AMAZONAS-BRASIL. ENHANCED MOISTURE CONVERGENCE AND PRECIPITABLE
WATER VALUES EXCEEDING 55-60MM WILL FAVOR EXTENSIVE AREAS OF HEAVY
RAIN-PRODUCING CONVECTION FROM NORTHERN PATO GROSSO INTO
AMAZONAS-BRASIL EXPECT 15-20MM/DAY AND MAXIMA OF 30-60MM...WHILE
IN SOUTHERN MATO GROSSO EXPECT MAXIMA OF 20-40MM. INTERACTIONS
WITH AN UPPER TROUGH WILL FAVOR HIGHER AMOUNTS IN SOUTHERN MINAS
GERAIS...WHERE EXPECT MAXIMA OF 40-80MM...WHILE IN SAP PAULO AND
SOUTHWEST RIO DE JANEIRO EXPECT MAXIMA OF 15-30MM.
GALVEZ...(WPC)
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