Prognostic Meteorological Discussion
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FXSA20 KWBC 061650
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1250 PM EDT FRI MAY 06 2016

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

MODEL DISCUSSION (VALID FROM MAY 06 AT 0000 UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS ARE IN GOOD AGREEMENT ON FORECAST EVOLUTION.
FORECAST CONFIDENCE IS HIGH.

MODELS CONTINUE SHOWING STRONG TROPOSPHERIC RIDGE BECOMING WELL
ENTRENCHED OVER THE SOUTHEAST PACIFIC/BELLINGSHAUSEN SEA. THE
FAIRLY STRONG RIDGE IS TO THEN PERSIST DURING THE NEXT SEVEN TO
TEN DAYS. AT LOW LEVELS THIS WILL SUSTAIN A RIDGE ACROSS THE
BELLINGSHAUSEN SEA TO PATAGONIA IN ARGENTINA. THE LOW LEVEL RIDGE
IS TO ALSO HOLD DURING THE NEXT SEVERAL DAYS...RESULTING IN ABOVE
NORMAL TEMPERATURES ACROSS MOST OF PATAGONIA-SOUTHERN CHILE AND
TIERRA DEL FUEGO.

IN THE MEAN TIME...STATIONARY FRONT LIES ACROSS URUGUAY-CENTRAL
ARGENTINA-NORTHERN PATAGONIA...ALONG THE NORTHWESTERN PERIPHERY OF
THE HIGH. THE FRONT WILL MEANDER IN THE REGION WHILE
WEAKENING...AND WILL BE THE FOCUS FOR LOW-LEVEL MOISTURE
CONVERGENCE THROUGH LATE SATURDAY. INITIALLY...EXPECTING MAXIMA OF
00-05MM/DAY THROUGH EARLY SATURDAY. AMOUNTS ARE TO PEAK ON
SATURDAY AS AN UPPER TROUGH APPROACHING CHILE SHEARS CYCLONIC
VORTICITY ACROSS THE ANDES. THIS WILL LEAD TO A FEW THUNDERSTORMS
WITH ACCUMULATIONS OF 15-20MM/DAY IN SOUTHERN CUYO/NORTHERN
PATAGONIA. AMOUNTS WILL DECREASE AFTER...WHILE PERIODS WITH
DRIZZLE AND LIGHT RAIN CONTINUE IN INTERIOR PORTIONS OF CENTRAL
ARGENTINA AND PATAGONIA THROUGH EARLY NEXT WEEK.

IN A SPLIT FLOW PATTERN...A WEAK SUBTROPICAL MOISTURE CONNECTION
WILL ARRIVE INTO SOUTHERN CHILE DURING SUNDAY...PARTICULARLY
BETWEEN THE BIO BIO AND LOS LAGOS REGIONS. THIS WILL LEAD TO
RAINFALL MAXIMA OF 05-10MM/DAY. OTHERWISE...EXPECTING SCATTERED
SNOW SHOWERS TO DOT THE CORDILLERA FROM THE SOUTHERN ANTOFAGASTA
REGION TO THE MAULE REGION ON A DAILY BASIS TO PRODUCE LIGHT
ACCUMULATIONS. MOST FREQUENT SNOW SHOWERS ARE EXPECTED ON
SATURDAY/SATURDAY EVENING...INCLUDING THE DEVELOPMENT OF LIGHT
RAIN SHOWERS IN INTERIOR PORTIONS OF CENTRAL CHILE.

ACTIVE PATTERN OF CONVECTION IS EXPECTED IN CENTRAL PORTIONS OF
THE CONTINENT...ESPECIALLY ACROSS PARAGUAY/MATO GROSSO DO SUL INTO
PARANA/SANTA CATARINA/SOUTHERN SAO PAULO. UPPER TROUGH WILL
CONTINUE TO INTERACT WITH SURFACE FRONT ON FRIDAY. THIS IS LEADING
TO STRONG THUNDERSTORMS FROM CENTRAL PARAGUAY/SOUTHERN MATO GROSSO
DO SUL INTO MISIONES/PARANA WHERE EXPECTING MAXIMA OF 25-50MM/DAY.
AS FRONT MEANDERS TO THE NORTH AND UPPER TROUGH PATTERN PERSISTS
OFF THE COAST OF NORTHERN CHILE...EXPECTING LEE TROUGH TO
INTENSIFY ALONG THE NORTHEASTERN ANDEAN SLOPES OF BOLIVIAN AND
SOUTHERN PERU. THIS WILL LEAD TO THUNDERSTORMS WITH MAXIMA OF
20-40MM/DAY DURING SATURDAY INTO EARLY SUNDAY. LATE ON
SUNDAY...MODELS ARE AGREEING ON A MORE ROBUST UPPER TROUGH
CROSSING THE ANDES. THIS WILL INTERACT WITH MOIST AND UNSTABLE AIR
MASS BREWING IN MID-SECTIONS OF THE CONTINENT. PRECIPITABLE WATER
IS FORECAST TO EXCEED 50MM...THE GDI 45...AND THE NORTHERLY
LOW-LEVEL JET IS FORECAST TO CONVERGE ALONG A FRONT FORECAST TO
EXTEND ACROSS PARANA-THE PARAGUAY-BRASIL BORDER-SOUTHERN BOLIVIA.
THIS WILL LEAD TO STRONG NOCTURNAL CONVECTION WITH ACCUMULATIONS
OF 25-50MM/DAY AND THE RISK FOR MCS FORMATION. THE ACTIVITY WILL
PEAK ON MONDAY WHEN EXPECTING MAXIMA OF 50-100MM/DAY AND CONTINUED
RISK FOR MCS FORMATION.

NORTH ACROSS THE CONTINENT...STRONGEST ACTIVITY WILL CLUSTER IN
THE NORTHERN AMAZON...SPECIFICALLY NORTHERN AMAZONAS IN BRASIL
INTO VENEZUELA/EASTERN COLOMBIA...WHERE EXPECTING DAILY MAXIMA OF
15-30MM/DAY. ACTIVE DIURNAL CONVECTION IS EXPECTED IN THE COASTAL
INTERIOR OF NORTHWESTERN ECUADOR...WHERE EXPECTING MAXIMA OF
15-20MM/DAY IN A DAILY BASIS AND VERY ISOLATED LARGER AMOUNTS.
ACTIVITY IS TO PEAK ON MONDAY...WHEN EXPECTING MAXIMA OF
20-40MM/DAY IN ASSOCIATION WITH AN INCREASE IN VENTILATION AND
INSTABILITY. OTHER REGION WITH ENHANCED CONVECTION WILL BE THE
EXTREME NORTHEASTERN COAST OF BRASIL...AS A WAVE IN THE TRADES
ARRIVES LATE ON SATURDAY. THIS WILL LEAD TO MAXIMA OF 15-20MM/DAY
DURING SATURDAY-SUNDAY...INCREASING TO 20-35MM/DAY DURING
SUNDAY-MONDAY.

ENRIQUEZ...DGAC (ECUADOR)
AYALA...DINAC (PARAGUAY)
GALVEZ...WPC (USA)

$$





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