388
FXSA20 KWBC 302003
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
303 PM EST THU JAN 30 2025

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

SOUTH AMERICAN FORECAST BULLETIN FOR 30 JAN 2025 AT 20 UTC:

AN UPPER TROUGH APROACHING THE SOUTHERN CONE WHILE PROPAGATING
NEAR 80W ON THURSDAY AFTERNOON IS INTERACTING QITH AN ATMOSPHERIC
RIVER THAT IS STIMULATING PRECIPITATION IN SOUTHERN CHILE. THE
MOIST PLUME IS FORECAST TO FAVOR MAXIMA OF 20 - 40MM IN AYSEN
THROUGH FRIDAY MORNING...WHILE FRONTAL CONVECTION FAVORS MAXIMA
GENERALLY UNDER 15MM IN LOS LAGOS/NORTHERN AYSEN. NOTE THE
HEAVIEST PRECIPITATION SOUTH OF THE COLD FRONT DUE TO DUNAMICS
ASSOCIATED WITH THE POTENT UPPER TROUGH. THE FRONT IS FORECAST TO
MEANDER NORTHWARD WHILE WEAKENING THEREAFTER. ANOTHER SURFACE
FRONT IS FORECAST TO ORGANIZE IN THE SOUTHERN CONE ON FRIDAY AND
BY FRIDAY THROUGH SATURDAY MORNING IT WILL FAVOR MAXIMA OF 15 -
30MM IN SOUTHWEST MAGALLANES.

EAST OF THE ANDES...DEEP-LAYER MOISTURE IS CLUSTERING TO ALTITUDES
NORTH OF 20-22S...WITH THE EXCEPTION OF SOUTHERN BRASILAND
SOUTHEAST PARAGUAY...WHERE PRECIPITABLE WATER VALUES OF 40 - 45MM
ARE FAVORING THE DEVELOPMENT OF DIURNAL CONVECTION ON THURSDAY. IN
THE MID-UPPER TROPOSPHERE...A BROAD TROUGH EXTENDS FROM A LOW NEAR
37S 47S INTO NORTHERN PARAGUAY AND SOUTHERN BOLIVIA. THIS TROUGH
IS VENTILATING CONVECTION FROM SOUTHERN BOLIVIA/FAR NORTHERN
PARAGUAY INTO EOUTHEAST BRASIL ON THURSDAY. THE NORTHERN TIER OF
THIS TROUGH IS FORECAST TO PROGRESS VERY SLOWLY THROUGH THE
FORECAST CYCLE WHILE EXPANDING INTO NORTHWEST BOLIVIA BY SATURDAY
EVENING...AS THE BOLIVIAN HIGH MEANDERS WEST INTO THE PACIFIC.
THIS EVOLUTION WILL HIGHLIGHT THE DRYING TREND IN MID-SECTIONS OF
THE CONTINENT AND ATTEMPT TO DEVELOP A SACZ-LIKE STRUCTURE IN
BRASIL AS THE WEEKEND PROGRESSES. GIVEN REMAINING UNCERTAINTIES ON
THE EVOLUTION OF THE LOW-LEVEL AND MID-LEVEL FLOW THE EVOLUTION IS
CURRENTLY BEING ANALYZED AS A LOW-LEVEL TROUGH IN OUR FORECAST
CHARTS. NEVERTHELESS...THE SACZ-LIKE STRUCTURE IS CONSISTENT WITH
THE PRECIPITATION PATTERN EXPECTED IN TROPICAL REGIONS OF BRASIL
AND ALSO CONSISTENT WITH INCREASING POTENTIAL FOR HEAVY
PRECIPITATION IN LARGER AREAS. THROUTGH EARLY FRIDAY EXPECT THE
HEAVIEST PRECIPITATION IN SOUTHEAST BRASIL FROM RIO DE JANEIVO
INTO MINAS GERAIS/SOUTHERN GOIAS WHERE EXPECT MAXIMA IN THE 30 -
60MM/DAY RANGE IN SCATTERED THUNDERSTORMS. SIMILAR AMOUNTS ARE
EXPECTED FROM SOUTHERN MARANHAN/TOCANTINS INTO SOUTHERN PARA. IN
NORTHWEST MATO GROSSO/RONDONIA INTO NORTHERN BOLIVIA AND THE
SOUTHERN AMAZON OF PERU EXPECT MAXIMA OF 20 - 40MM. ON FRIDAY
THROUGH EARLY SATURDAY EXPECT THE HEAVIEST PRECIPITATION IN SAO
PAULO AND RIO DE JANEIRO/SOUTHWEST MINAS GERAIS WHERE EXPECT
MAXIMA OF 30 - 60MM. IN MATO GROSSO/EASTERN BOLIVIA AND RONDONIA
EXPECT MAXIMA OF 20 - 45MM...WHILE IN MARANHAO AND SOUTHEAST PARA
EXPECT MAXIMA OF 30 - 60MM. BY FRIDAY THROUGH EARLY SATURDAY
EXPECT MAXIMA OF 35 - 70MM IN SOUTHEAST BRASIL WHILE EXPECT MAXIMA
25 - 50MM FROM SOUTHWEST MINAS GERAIS INTO SOUTHERN PARA/NORTHERN
MATO GROSSO.

A REGION WHERE EXPECT ACTIVE DIURNAL CONVECTION IS THE ALTIPLANO
AND THE ANDES OF SOUTHERN PERU. ENHANCED MOIST EASTERLY FLOW IN
THE MID AND UPPER TROPOSPHERE WILL CONTINUE TO PROVIDE SUFFICIENT
MOISTURE FOR SCATTERED THUNDERSTORMS. AS THE AFOREMENTIONED UPPER
TROUGH IN THE NORTHERN STREAM DEEPENS...EXPECT INCREASING
ADVECTION OF DRY AIR FROM THE PACIFIC BASIN INTO THE SOUTHERN
ALTIPLANO...WHICH WILL YIELD TO A DECREASING TREND IN
PRECIPITATION THROUGH THE WEEKEND. IN PERU...EXPECT A NORTHWARD
MIGRATION OF THE REGIONS WITH THE POTENTIAL FOR THE HEAVIEST
PRECIPITATION. ON THURSDAY THROUGH EARLY FRIDAY EXPECT MAXIMA OF
15 - 20MM IN SOUTHERN PERU AND MOST OF THE CENTRAL AND NORTHERN
ALTIPLANO IN BOLIVIA. ON FRIDAY THROUGH EARLY SATURDAY EXPECT
MAXIMA OF 15 - 30MM FROM NORTHERN BOLIVIA INTO MOST OF SOUTHERN
PERU WHILE IN CENTRAL PERU EXPECT MAXIMA OF 15MM. ON
SATURDAY...EXPECT ACTIVE CONVECTION IN THE CENTRAL PERUVIAN
ANDES...WHILE IN THE CENTRAL AMAZON OF PERU EXPECT MAXIMA OF 30 -
60MM WITH A RISK FOR MCS FORMATION.

ALSO ON SATURDAY...THE WESTERN TAIL OF A WEAKENING COLD FRONT WILL
ENHANCE LOW-LEVEL MOISTURE CONVERGENCE IN LA PAMPA/SOUTHERN BUENOS
AIRES PROVINCE. AS THIS INTERACTS WITH A SHORT WAVE UPPER TROUGH
EXPECT THE POTENTIAL FOR HEAVY THUNDERSTORMS AND VERY ISOLATED
MAXIMA OF 15 - 30MM.

GALVEZ...(WPC)
$$