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348
FXSA20 KWBC 291505
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1104 AM EDT WED OCT 29 2014

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

MODEL DISCUSSION (VALID FROM OCTOBER 29 AT 00UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS CONTINUE IN GOOD AGREEMENT ON FORECAST
EVOLUTION. FORECAST CONFIDENCE IS HIGH.

COLD AIRMASS IS ENTERING THE SOUTHERN CONE. COLD FRONT AND
OCCLUDED LOW ARE ALREADY IMPINGING INTO THE MAGALLANES AND
SOUTHERN AYSEN REGIONS IN CHILE. THIS WILL SUSTAIN SEVERAL ROUNDS
WITH LIGHT TO MODERATE SNOW SHOWERS DURING THE DAY TODAY WITH
ACCUMULATIONS UP TO 5 CM OF SNOW IN SOME LOCATIONS. FURTHER NORTH
ACROSS PARTS OF SOUTHERN CHILE...EXPECTING ACCUMULATIONS OF
10-15MM/DAY DECREASING AFTERWARDS. SHOWERS OF WET SNOW ARE ALSO
POSSIBLE IN SOUTHEASTERN PARTS OF PATAGONIA THROUGH THE DAY ON
THURSDAY...TAPERING OFF AFTERWARDS.

OTHER REGION OF INTEREST IS THE RIO DE LA PLATA BASIN. AS LARGE
TROUGH PUSHES FROM THE WEST...EXPECTING SEVERAL ROUNDS OF CYCLONIC
VORTICITY ADVECTION AND HEIGHT FALLS TO CONTINUE STIMULATING
THUNDERSTORM DEVELOPMENT IN THE REGION. FURTHERMORE...INSTABILITY
AND LOW-LEVEL MOISTURE CONVERGENCE AHEAD OF A LOW-LEVEL JET
CONTINUE FAVORABLE FOR STRONG THUNDERSTORMS WITH HEAVY RAINFALL
OVER THE REGION. EXPECTING HIGHEST AMOUNTS ACROSS THE EASTERN
BUENOS AIRES PROVINCE AND MOST OF URUGUAY REACHING MAXIMA OF
50-100MM/DAY THROUGH EARLY THURSDAY. ISOLATED HIGHER AMOUNTS ARE
EXPECTED IN STRONGEST THUNDERSTORMS. DURING THURSDAY INTO
FRIDAY...STRONGEST CONVECTION WILL CONCENTRATE ACROSS THE UPPER
MESOPOTAMIA REGION TO PRODUCE MAXIMA OF 20-45MM/DAY FROM
SOUTHEASTERN PARAGUAY INTO MISIONES AND THE INTERIOR OF SOUTHERN
BRASIL. LATER IN THE CYCLE...AS THE BOLIVIAN HIGH RESTRUCTURES
FROM SOUTHERN PERU INTO SOUTHERN BOLIVIA...VENTILATION WILL
INCREASE IN THE REGION. FURTHERMORE...AN INTENSIFICATION OF THE
CHACO LOW BY THURSDAY INTO FRIDAY WILL LEAD TO THE ADVECTION OF
MOISTURE AND INSTABILITY FROM SOUTHWESTERN BRASIL INTO THE CHACO
PARAGUAYO AND EASTERN BOLIVIA. UNDER AN INTENSIFICATION OF
EASTERLY/SOUTHEASTERLY LOW-LEVEL WINDS...EXPECTING AN INCREASE IN
CONVECTION ACROSS SOUTHERN BOLIVIA WITH ACCUMULATIONS INCREASING
TO 20-45MM/DAY ACROSS MOST OF EASTERN BOLIVIA AND THE NORTHEASTERN
FOOTHILLS OF CENTRAL BOLIVIA/SOUTHERN PERU. THE GFS IS NOW LESS
CONFIDENT ABOUT A STRONG SOUTHERLY SURGE DEVELOPING ALONG EASTERN
BOLIVIA INTO SOUTHERN PERU. HOWEVER...MODELS ARE STILL AGREEING ON
STRONG 10-15KT EASTERLIES AND ENHANCED MOISTURE CONVERGENCE BY THE
FLOW AND THE ANDES TO DOMINATE MOST OF THE LOWLANDS OF BOLIVIA BY
MID-LATE CYCLE. THIS WILL LEAD TO AN INCREASE IN ACCUMULATIONS. BY
SATURDAY...EXPECTING STRONG THUNDERSTORMS TO PRODUCE SCATTERED
MAXIMA OF 50-100MM/DAY WITH THE RISK OF MCS FORMATION. HEAVY
RAINFALL IS ALSO EXPECTED ON SUNDAY...WITH A DECREASING TREND IN
ACCUMULATIONS.

ACROSS BRASIL...LOCALLY HEAVY RAINS ARE STILL POSSIBLE THROUGH THE
DAY ON THURSDAY...AS UPPER AND LOW-LEVEL TROUGHS MEANDER ACROSS
GOIAS/NORTHERN MINAS GERAIS INTO CENTRAL PORTIONS OF BAHIA.
EXPECTING SCATTERED MAXIMA OF 20-45MM/DAY WITH ISOLATED HIGHER
AMOUNTS IN STRONGEST STORMS. AREAS OF STRONGEST CONVECTION WILL
SLOWLY MEANDER WEST SOUTHWESTWARD THROUGH THE CYCLE AS THE
BOLIVIAN HIGH REORGANIZES FROM THE WEST AND BROAD REGIONS OF
MOISTURE CONVERGENCE REORGANIZE ACROSS CENTRAL/WESTERN SOUTH
AMERICA. OTHER REGION WITH SCATTERED DIURNAL THUNDERSTORMS WILL BE
THE SELVA ALTA/YUNGAS OF PERU AND NORTHERN BOLIVIA...WHERE
EXPECTING EARLY MORNING THUNDERSTORMS TO PRODUCE SCATTERED MAXIMA
OF 15-35MM/DAY.

CAROCA...DMC (CHILE)
DURAN...SENAHMI (PERU)
GALVEZ...WPC (USA)
$$






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