575
FXSA20 KWBC 181931
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
230 PM EST MON NOV 18 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 18 NOV 2024 AT 1800 UTC:
ANALYSIS OF LARGE SCALE CONDITIONS SHOWS THAT THE MJO IS BECOMING
UPPER CONVERGENT OVER THE AMERICAS. ALTHOUGH THIS GENERALLY MEANS
A DECREASE IN THE COVERAGE OF AREAS PRONE TO HEAVY
PRECIPITATION...A FEW SYNOPTIC SYSTEMS IN THE REGION WILL
HIGHLIGHT PRECIPITATION. OF INTEREST IS THE INFLUENCE OF A ROBUST
BOLIVIAN HIGH/SUBTROPICAL UPPER RIDGE...WHICH IS VELTILATING DEEP
CONVECTION IN TROPICAL AND SUBTROPICAL PORTIONS OF THE CONTINENT.
A SLOW-TO-PROGRESS MID-UPPER TROUGH PATTERN IS ESTABLISHED OVER
THE BELLINGSHAUSEN SEA. SEVERAL SHORTER VORTICES ARE REVOLVING
AROUNG THE MAIN TROUGH. IN THE LOW LEVELS...A SYSTEM OF INTEREST
IS AN ESTRATROPICAL CYCLONE CENTERING ON A LOW NEAR 45S 93W ON
MONDAY AFTERNOON. THIS SYSTEM IS FORECAST TO ENTER THE SOUTHERN
CONE DURING THE DAY ON TUESDAY. THIS WILL FAVOR MAXIMA OF 15-20MM
IN AYSEN AND WESTERN MAGALLANES AND BOUNDARY LAYER WINDS OF
50-60KT IN THE WESTERN DRAKE PASSAGE AND SOUTHWEST TIERRA DEL
FUEGO ON TUESDAY AFTERNOON. THE NEXT FRONT ARRIVING IN THE
WESTERLIES IS EXPECTED ON THURSDAY...HOWEVER...MOIST ONSHORE FLOW
WILL FAVOR ISOLATED MAXIMA OF 15-20MM IN SOUTHERN AYSEN AND
MAGALLANES ON WEDNESDAY.
THE BOLIVIAN HIGH IS WELL ESTABLISHED IN MID-SECTIONS OF THE
CONTINENT...WHILE CENTERING OVER NORTHWEST PARAGUAY ON MONDAY.
SHORT WAVE MID-UPPER TROUGHS ARE PROPAGATING EASTWARD ALONG THE
SOUTHERN PERIPHERY OF THE HIGH. OF INTEREST IS A TROUGH FORECAST
TO CROSS THE ANDES EARLY ON TUESDAY. THIS WILL INTERACT WITH A
MOIST POOL OF PRECIPITABLE WATER EXCEEDING 50MM ACROSS FAR
NORTHERN ARGENTINA AND PARAGUAY TO FAVOR STRONG CONVECTION. IN THE
LOW-LEVELS...A FRONT EXTENDS ACROSS RIO GRANDE DO SUL...SOUTHWEST
PARAGUAY...AND EXTENDS ALONG AN ILL-DEFINED BOUNDARY ACROSS THE
CHACO. AS THE UPPER TROUGH PROGRESSES EASTWARD...EXPECT
CYCLOGENESIS TO DEVELOP IN CORRIENTES/SOUTHEAST PARAGUAY ON
TUESDAY. AS THE SYSTEM MOVES EASTWARD...EXPECT THE SURFACE LOW TO
CENTER NEAR 29S 45W BY WEDNESDAY EVENING. EXPECT STRONG CONVECTION
TO DEVELOP IN NORTHEAST ARGENTINA LATE ON MONDAY...WHICH WILL
FAVOR MAXIMA OF 30-60MM. ON TUESDAY...EXPECT THE LARGEST
ACCUMULATIONS TO CLUSTER IN THE COLD SIDE OF THE SURFACE FRONT
ACROSS RIO GRANDE DO SUL/CORRIENTES AND NORTHERN URUGUAY...WHERE
MAXIMA WILL LIKELY REACH 35-70MM/DAY WITH A RISK FOR ECHO
TRAINING. BY WEDNESDAY...ONSHORE FLOW INTO SANTA CATARINA/EASTERN
RIO GRANDE DO SUL WILL FAVOR MAXIMA OF 30-60MM AIDED BY OROGRAPHIC
UPLIFT.
IN AREAS TO THE NORTH...THE MOST ACTIVE CONVECTION IS ORGANIZING
IN PARAGUAY AND BOLIVIA...GIVEN HIGH VALUES OF PRECIPITABLE
WATER...THE AFOREMENTIONED BOUNDARY AND VENTILATION BY THE
BOLIVIAN HIGH. THE AFOREMENTIONED BOUNDARY ACROSS THE CHACO IS
FORECAST TO LOSE DEFINITION THROUGH TUESDAY...WHICH WILL FAVOR A
DECREASE IN DAILY RAINFALL ACCUMULATION. YET...EXPECT STRONG
CONVECTION THROUGH EARLY TUESDAY...WHICH WILL FAVOR MAXIMA OF
30-60MM/DAY IN MOST OF PARAGUAY...LOWER BOLIVIA AND MATO GROSSO DO
SUL. THIS WILL EVOLVE INTO MAXIMA OF 20-35MM THEREAFTER.
ANOTHER REGION OF INTEREST ARE THE ANDEAN FOOTHILS AND AMAZON OF
SOUTHERN PERU AND NORTHERN BOLIVIA. HIGH VALUES OF PRECIPITABLE
WATER...VENTILATION BY THE BOLIVIAN HIGH AND NORTHEASTERLY
LOW-LEVEL FLOW WILL HIGHLIGHT THE DEVELOPMENT OF MOIST CONVECTION
ON A DAILY BASIS. ON MONDAY EXPECT MAXIMA OF 30-60MM IN CENTRAL
PERU AND NORTH-CENTRAL BOLIVIA. ON TUESDAY EXPECT MAXIMA OF
20-45MM. ON WEDNESDAY EXPECT MAXIMA OF 30-60MM IN PERU WHILE IN
BOLIVIA EXPECT MAXIMA OF 25-50MM.
GALVEZ...(WPC)
LOPEZ...(DMH-PARAGUAY)
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