Prognostic Meteorological Discussion
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FXSA20 KWBC 261659
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1259 PM EDT FRI AUG 26 2016

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

MODEL DISCUSSION (VALID FROM AUG 26 AT 0000 UTC): FORECAST
CONFIDENCE CONTINUES HIGH THROUGH THE CYCLE IN ASSOCIATION WITH
SIMILAR SOLUTIONS FOR THE CURRENT LONG WAVE PATTERN IN SOUTH
AMERICA.

SYSTEM OF CONCERN IS LONG WAVE UPPER TROUGH THAT WILL CROSS THE
ANDES OF NORTHERN CHILE ON SATURDAY THROUGH MONDAY. THIS TROUGH
WILL INTERACT AND STIMULATE THE NORTHWARD PROGRESSION OF A FRONT
THAT WILL PROPAGATE ACROSS THE RIO DE LA PLATA BASIN ON
FRIDAY...URUGUAY-NORTHERN ARGENTINA ON SATURDAY...RIO GRANDE DO
SUL-CENTRAL PARAGUAY-SOUTHERN BOLIVIA ON SUNDAY...AND MATO GROSSO
DO SUL...CENTRAL BOLIVIA ON MONDAY EVENING. MOISTURE CONTENT IS
INCREASING IN THE RIO DE LA PLATA BASIN UNDER THE INFLUENCE OF A
LOW-LEVEL JET FROM THE NORTH. EXPECTING PRECIPITABLE WATER IN THE
ORDER OF 40MM THROUGH THE CYCLE. CONVECTION WILL START IN THE RIO
DE LA PLATA BASIN LATE ON FRIDAY/EARLY SATURDAY TI PRODUCE MAXIMA
OF 15-30MM/DAY IN URUGUAY. ACCUMULATIONS WILL LARGELY INCREASE
DURING SATURDAY...WHEN EXPECTING MAXIMA OF 40-80MM/DAY IN CENTRAL
URUGUAY...AND MAXIMA OF 20-40MM IN NORTHERN ARGENTINA. BY SUNDAY
INTO EARLY MONDAY...LARGEST AMOUNTS WILL CENTER IN
FORMOSA/CENTRAL-SOUTHEASTERN PARAGUAY INTO MISIONES/CORRIENTES.
THE LIMITED INSTABILITY WITH THIS SYSTEM WILL REDUCE THE RISK FOR
SEVERE CONVECTION AND ESPECIALLY HAIL. NEVERTHELESS...LOW-LEVEL
MOISTURE CONVERGENCE AND THE UPPER DIVERGENT PATTERN WILL BE
FAVORABLE FOR ISOLATED SEVERE CONVECTION AND LARGE RAINFALL
AMOUNTS. EXPECTING MAXIMA IN THE ORDER OF 35-70MM/DAY. NORTH
ACROSS THE CHACO PARAGUAYO AND SOUTHERN/CENTRAL BOLIVIA EXPECTING
MAXIMA OF 20-45MM.  BY MONDAY-TUESDAY LARGEST AMOUNTS ARE EXPECTED
IN NORTHERN BOLIVIA/SOUTHERN BOLIVIA WHERE EXPECTING MAXIMA OF
25-50MM/DAY AND ISOLATED LARGER AMOUNTS IN INTERACTION WITH
OROGRAPHY. ALONG THE FRONT IN SOUTHWESTERN MATO GROSSO/MATO GROSSO
DO SUL EXPECTING MAXIMA OF 15-30MM/DAY. ACROSS SOUTHEASTERN
PARAGUAY INTO SANTA CATARINA/PARANA EXPECTING MAXIMA OF 25-50MM
WITH A SLIGHT RISK FOR SEVERE CONVECTION. BY TUESDAY INTO
WEDNESDAY LARGEST ACCUMULATIONS WILL ORGANIZE ALONG A SHEAR
LINE/EDGE OF THE SOUTHERLY SURGE IN CENTRAL PERU...WHERE EXPECTING
MAXIMA OF 25-50MM/DAY.

ANOTHER FEATURE OF INTEREST IS A SUBTROPICAL MOISTURE CONNECTION
ARRIVING IN SOUTHERN CHILE ON MONDAY. THIS WILL ARRIVE ACCOMPANIED
BY THE DIVERGENT EXIT OF AN UPPER JET...TO SUSTAIN MAXIMA OF
20-40MM/DAY IN THE AYSEN REGION AND MAXIMA OF 15-20MM/DAY BETWEEN
VALDIVIA/OSORNO AND PUERTO MONTT.

OSORIO...DMC (CHILE)
CASTILLO...UCR (COSTA RICA)
ALVA...SENAMHI (PERU)
GALVEZ...WPC (USA)
$$





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