273
FXSA20 KWBC 311806
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
205 PM EDT THU OCT 31 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 31 OCT 2024 AT 1900 UTC:
OBSERVATIONS AND MODELS CONTINUE SHOWING THAT THE MJO IS BECOMING
INCREASINGLY UPPER DIVERGENT OVER SOUTH AMERICA. AS THIS ENHANCES
VENTILATION IN THE LARGE SCALE...EXPECT AN INCREASE IN THE REGIONS
OF MODERATE AND HEAVY PRECIPITATION PRODUCED BY SIGNIFICANT
WEATHER SYSTEMS IN THE NEXT SEVEN DAYS.
A POTENT UPPER TROUGH IS PROPAGATING EASTWARD ACROSS THE EASTERN
PACIFIC WHILE EXTENDING ALONG 90W-93W THIS MORNING. THIS TROUGH IS
ACCOMPANIED BY FORMIDABLE UPPER JET DYNAMICS...INCLUDING THE
LEFT/COLD EXIT OF AN UPPER JET ALONG 35S AND A NEGATIVELY TILTED
SHORT WAVE TROUGH. AS A RESULT...THE ASSOCIATED ATMOSPHERIC RIVER
IS PRODUCING DEEP CONVECTION AND AREAS OF HEAVY PRECIPITATION WEST
OF 80W AND SOUTH OF 35S. THIS SYSTEM IS FORECAST TO ENTER SOUTHERN
CHILE EARLY ON FRIDAY AND THE FRONT IS FORECAST TO MEANDER INTO
CENTRAL CHILE BY FRIDAY EVENING TO THEN WEAKEN. ALTHOUGH THE
DYNAMICS AND AVAILABLE MOISTURE ARE IMPORTANT...THE SURFACE FRONT
IS FORECAST TO ARRIVE WITH A PROMINENT MERIDIONAL COMPONENT WHICH
WILL LIMIT PRECIPITATION AMOUNTS. EAST OF THE ANDES...THE RAPID
PROGRESSION OF THE FRONTAL SYSTEM WILL DEVELOP A PREFRONTAL SQUALL
LINE ON FRIDAY...FORECAST TO EXTEND ACROSS THE SOUTHWEST BUENOS
AIRES PROVINCE INTO SOUTHERN MENDOZA BY FRIDAY EVENING. THIS
ASSOCIATES WITH AN ELEVATED RISK FOR SEVERE CONVECTION INCLUDING
LARGE HAIL. EXPECT MAXIMA OF 30-60MM/DAY WITH THIS SYSTEM.
ANOTHER SYSTEM OF INTEREST IS A SECOND MID-UPPER TROUGH CURRENTLY
LOCATED WEST OF 120W. THIS TROUGH IS FORECAST TO APPROACH SOUTHERN
CHILE ON SATURDAY AND CROSS THE SOUTHERN CONE THROUGH MONDAY. AS
THE TROUGH AMPLIFIES ON SATURDAY...EXPECT THE STRENGTHENING OF AN
UPPER JET...FORECAST TO ENHANCE VENTILATION IN AREAS SOUTH OF LOS
RIOS NEAR 40S. GIVEN AN ENHANCED MERIDIONAL COMPONENT OF THIS NEW
FRONT...THE HEAVIEST PRECIPITATION IS FORECAST TO CLUSTER IN AREAS
TO THE SOUTH OF 45S IN AYSEN AND NORTHERN MAGALLANES ON
SATURDAY...WHERE EXPECT MAXIMA OVER 50MM/DAY. ON SUNDAY EXPECT
PRECIPITATION TO EXTEND INTO THE CORDILLERA OF NUBLE AND BIO BIO.
IN THE NORTHERN STREAM...A TROUGH EXTENDS NEAR 80W AND IS FORECAST
TO CROSS THE ANDES OF NORTHERN ARGENTINA...BOLIVIA AND SOUTHERN
PERU THROUGH SATURDAY MORNING. THIS TROUGH IS ALREADY LOWERING THE
PRESSURES IN NORTHWEST ARGENTINA AND ENHANCING MOISTURE
CONVERGENCE. PRECIPITABLE WATER ANALYSIS SHOWS VALUES APPROACHING
50MM. THIS IS ALREADY RESULTING IN SCATTERED STRONG THUNDERSTORMS
FROM NORTHWEST ARGENTINA INTO MOST OF THE PARAGUAYAN
CHACO...INCLUDING CENTRAL PARAGUAY. GIVEN THAT THIS WILL BE A
SLOW-TO-EVOLVE SYSTEM...EXPECT SEVERAL DAYS OF HEAVY PRECIPITATION
IN MID-SECTIONS OF THE CONTINENT. ON THURSDAY...EXPECT MAXIMA OF
40-80MM FROM FAR NORTHWEST ARGNETINA INTO SOUTHERN BOLIVIA AND IN
THE PARAGUAYAN CHACO...INCLUDING A SLIGHT RISK FOR SEVERITY. IN
CENTRAL PARAGUAY AND NORTH-CENTRAL ARGENTINA EXPECT MAXIMA OF
20-40MM/DAY WITH A MARGINAL RISK FOR SEVERITY. ON FRIDAY...EXPECT
THE HEAVIEST RAINFALL AMOUNTS IN MOST OF PARAGUAY/PANTANAL...WHERE
EXPECT MAXIMA OF 30-60MM/DAY AND A RISK FOR MCS FORMATION. UNDER
THE INFLUENCE OF AN UPPER TROUGH MOVING EAST ACROSS SOUTHERN PERU
AND BOLIVIA...EXPECT ENHANCEMENT OF CONVECTION ACROSS THE
SOUTHWEST AMAZON BASIN...WHICH WILL FAVOR MAXIMA OF 20-45MM IN
CENTRAL BOLIVIA AND SIMILAR AMOUNTS IN MATO GROSSO.
GALVEZ...(WPC)
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