970
FXSA20 KWBC 092044
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
444 PM EDT WED OCT 09 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 09 OCT 2024 AT 2100 UTC:

A ROBUST UPPER TROUGH CROSSING THE ANDES OF CENTRAL AND NORTHERN
CHILE CONTINUES BEING THE SYSTEM OF CONCERN. THE SLOW-TO-EVOLVE
SITUATION IS ALLOWING FOR THE BUILD UP OF HIGH VALUES OF
PRECIPITABLE WATER IN CENTRAL PORTIONS OF THE CONTINENT. ALTHOUGH
MADDEN-JULIAN CONDITIONS ARE GENERALLY UPPER CONVERGENT...THE
SYNOPTIC SITUATION AND BUILD UP OF PRECIPITABLE WATER IS
SUFFICIENTLY SIGNIFICANT TO CONTINUE FAVORING THE DEVELOPMENT OF
STRONG CONVECTION AND LOCALLY HEAVY PRECIPITATION. NOTE THAT
MODELS SEEM TO NOT BE CAPTURING THE PROPER AMOUNTS OF AVAILABLE
MOISTURE IN THE REGION...WITH THE ECMWF BEING MOST IN TUNE WITH
OBSERVATIONS AND SATELLITE DERIVATIONS. IN THE LOW-LEVELS...A
STATIONARY FRONT EXTENDS ALONG 20N FROM MINAS GERAIS-BRASIL INTO
SOUTHERN BOLIVIA. ALTHOUGH THIS IS LIMITING THE TROPICAL AIR MASS
TO LOCATIONS NORTH OF THIS BOUNDARY...EXPECT THE HEAVIEST
PRECIPITATION TO CLUSTER SOUTH...PRIMARILY ASSOCIATED WITH UPPER
TROUGH AND UPPER JET DYNAMICS.

ON WEDNESDAY...EXPECT THE HEAVIEST PRECIPITATION ALONG EASTERN
PORTIONS OF SANTA CATARINA AND SOUTHERN PARANA IN BRASIL WHERE
ENHANCED ONSHORE FLOW WILL FAVOR 20-40MM/DAY AND MAXIMA OF
50-100MM. MODERATE PRECIPITATION IS ALSO EXPECTED IN ARAS WEST
INTO CENTRAL PARAGUAY AND MATO GROSSO DO SUL. IN CENTRAL PARAGUAY
AND MATO GROSSO DO SUL EXPECT MAXIMA OF 20-45MM AND A MARGINAL
RISK FOR SEVERITY...WHILE IN SOUTHEAST
PARAGUAY...MISIONES-ARGENTINA INTO SOUTHWEST PARANA/WEST SANTA
CATARINA EXPECT MAXIMA OF 35-70MM. ALSO ON WEDNESDAY...MOIST
UPSLOPE WINDS AND ASCENT INDUCED BY THE UPPER TROUGH WILL CONTINUE
TO FAVOR MODERATE AMOUNTS IN INTERIOR PORTIONS OF NORTHWEST
ARGENTINA...WHERE EXPECT ISOLATED MAXIMA OF 20-40MM. IN THE SIERRA
DE CORDOBA EXPECT MAXIMA OF 15-30MM. ON THURSDAY...EXPECT THE
COMBINATION OF UPPER TROUGH AND UPPER JET DYNAMICS AND AVAILABLE
MOISTURE TO PEAK IN EASTERN PARAGUAY AND PARANA/SANTA CATARINA IN
BRASIL. NOTE THAT THE DIVERGENT ENTRANCE OF AN ANTICYCLONICALLY
CURVED UPPER JET WILL LIKELY ENHANCE DYNAMICALLY-INDUCED ASCENT IN
THE REGION. EXPECT AMOUN TS OF 25-50MM/DAY AND MAXIMA OF
75-125MM...ALTHOUGH ISOLATED HIGHER AMOUNTS ARE POSSIBLE. MODERATE
PRECIPITATION IS ALSO EXPECTED IN RIO GRANDE DO SUL WHERE EXPECT
MAXIMA IN THE 20-40MM/DAY RANGE. AS CYCLOGENSIS DEVELOPS DURING
THIS PERIOD...EXPECT A COLD FRONT TO START TO MEANDER NORTHWARD
ACROSS CENTRAL BOLIVIA. AS THE FRONT INTERACTS WITH THE LOW-LEVEL
JET EXPECT MAXIMA OF 25-50MM. ON FRIDAY...EXPECT THE HEAVIEST
PRECIPITATION TO CLUSTER IN SOUTHEAST BRASIL BETWEEN PARANA AND
WEST RIO DE JANEIRO AND SOUTHWEST MINAS GERAIS...MOSTLY DUE TO MID
AND UPPER LEVEL FORCING ASSOCIATED WITH THE UPPER TROUGH. EXPECT
15-20MM/DAY AND ISOLATED MAXIMA OF 25-50MM INCLUDING A MARGINA
RISK FOR SEVERE WEATHER. ANOTHER AREA OF MODERATE ACCUMULATIONS
WILL BE CENTRAL AND NORTHERN BOLIVIA...WHERE THE RETURN OF THE
LOW-LEVEL JET FROM THE NORTHWEST WILL FAVOR SUFFICIENT ISENTROPIC
LIFT TO TRIGGER MAXIMA OF 15-30MM. SIMILAR AMOUNTS ARE EXPECTED
ALONG THE EASTERN CORDILLERA OF CENTRAL AND SOUTHERN PERU...AIDED
BY ANOTHER UPPER TROUGH FORECAST TO REFORM OVER THE REGION ON
FRIDAY.

ANOTHER PROCESS OF INTEREST IS ECHO TRAINING OCCURRING ALONG A
SURFACE FRONT IN ESPIRITO SANTO ON WEDNESDAY. THIS WILL FAVOR
MAXIMA OF 25-50MM THROUGH EARLY THURSDAY. FRMO THURSDAY INTO EARLY
FRIDAY EXPECT THE RISK FOR MODERATE PRECIPITATION TO EXPAND
WESTWARD INTO MINAS GERAIS...WHERE EXPECT MAXIMA OF 20-45MM.

GALVEZ...(WPC)

$$