Prognostic Meteorological Discussion
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000
FXSA20 KWBC 231618
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1218 PM EDT MON MAY 23 2016

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

MODEL DISCUSSION (VALID FROM MAY 23 AT 0000 UTC): OVER THE EASTERN
PACIFIC...IN A SPLIT FLOW PATTERN...THE FLOW DIVIDES BETWEEN A
RIDGE ON THE SOUTHERN STREAM AND A TROUGH TO THE NORTH. THE RIDGE
IS TO MEANDER ACROSS THE BELLINGSHAUSEN SEA TO SOUTHERN PORTIONS
OF CHILE DURING THE NEXT COUPLE OF DAYS...AND THROUGH 72-96 HRS IT
IS TO SLOWLY MIGRATE ACROSS PATAGONIA TO THE WESTERN ATLANTIC.
MEANWHILE...THIS IS TO SUSTAIN A STRONG CAP INVERSION AND ABOVE
NORMAL TEMPERATURES. THE NORTHERN STREAM TROUGH...MEANWHILE...IS
FORECAST TO GRADUALLY WEAKEN AS IT MEANDERS EAST INTO CENTRAL
PORTIONS OF CHILE BY 48-96 HRS. AT LOW LEVELS IT IS TO SUSTAIN A
BROAD TROUGH OFF THE COAST OF CHILE EARLY IN THE CYCLE. THROUGH
72-84 HRS IT IS TO WEAKEN/NEARLY DISSIPATE WHILE MEANDERING EAST.
ALTHOUGH GLOBAL MODELS SUGGEST POSSIBILITY OF MODERATE RAINFALL
AMOUNTS...EROSION OF ENERGY AND AVAILABLE MOISTURE IS LIKELY TO
PRODUCE LESSER AMOUNTS THAN WHAT THE GUIDANCE SUGGESTS. MOST
ACTIVE IS LIKELY TO DEVELOP NEAR CONCEPCION CHILE EARLY ON TUESDAY
MORNING...WHERE THE MAXIMA IS TO PEAK AT 15-20MM. OTHERWISE...ONLY
EXPECTING LIGHT RAINFALL AMOUNTS WITH ACCUMULATION OF 00-05MM.

AS THE MID LEVEL RIDGE MEANDERS OVER SOUTHERN CHILE/PATAGONIA...IT
IS TO INDUCE THE NORTHWARD AMPLIFICATION OF A TROUGH ACROSS THE
DRAKE PASSAGE INTO THE WESTERN ATLANTIC BY 36-48 HRS. THROUGH 72
HRS THE TROUGH IS TO THEN RAPIDLY DEEPEN ACROSS RIO DE LA PLATA
BASIN/URUGUAY...WITH BROAD TROUGH TO DOMINATE THE SOUTH ATLANTIC
BY 96-132 HRS. AT LOW LEVELS THIS IS TO SUSTAIN A BROAD TROUGH AND
A PROGRESSIVE FRONT THAT LIFTS ACROSS TIERRA DEL FUEGO TO SOUTHERN
PATAGONIA THROUGH 30-36 HRS. A BUILDING 1037 HPA HIGH OVER
SOUTHERN PATAGONIA IS TO THEN FAVOR THE NORTHWARD PROGRESSION OF
THIS BOUNDARY ACROSS LA PAMPA TO BUENOS AIRES PROVINCE BY 72
HRS...INTO URUGUAY/SOUTHERN BRASIL BY 96 HRS. AT 96 HRS THE FRONT
SURGES NORTH INTO SOUTHERN BRASIL-PARAGUAY. AS IT PUSHES NORTH
INTO MID SECTIONS OF SOUTH AMERICA THIS WILL TRIGGER LIGHT TO
MODERATE CONVECTION... WITH MAXIMA OF 15-25MM EXPECTED ACROSS
PARAGUAY WHILE OVER SOUTHEAST/SOUTHERN BRASIL THE MAXIMA IS TO
PEAK AT 20-40MM. THE BUILDING RIDGE IS TO THEN SUSTAIN A BRISK
EASTERLY FLOW ACROSS NORTHERN PATAGONIA/LA PAMPA...TO FAVOR LIGHT
AS IT LIFTS ADIABATICALLY ACROSS THE SOUTHERN ANDES. BY 60-84 HRS
THIS IS TO THEN FAVOR RAINFALL AMOUNTS OF 05-10MM ACROSS NORTHERN
PATAGONIA-LA PAMPA...WITH CHANCE OF SNOWFALL OVER THE HIGHER
ELEVATIONS.

NORTH OVER THE CONTINENT...AT 200 HPA...A CROSS EQUATORIAL TROUGH
LIES EAST OF THE GALAPAGOS ISLANDS. THIS TROUGH...AS IT MEANDERS
OFF THE COAST OF ECUADOR...IS TO FAVOR AN UPPER DIVERGENT PATTERN
ACROSS PERU-SOUTHERN COLOMBIA/NORTHWEST BRASIL. THIS IS TO VENT
DEEP CONVECTION EARLY IN THE CYCLE TO SUSTAIN MAXIMA OF 30-60MM.
THROUGH 48-60 HRS THIS WILL DECREASE TO 20-40MM...AND BY 60-84 HRS
IT IS TO PEAK AROUND 15-25MM. OTHER CONVECTION IS EXPECTED ACROSS
EASTERN BAHIA-RIO GRANDE DO NORTE IN NORTHEAST BRASIL...WHERE A
PREFRONTAL SHEAR LINE IS TO SUSTAIN SCATTERED CONVECTION OVER THE
NEXT FEW DAYS. IN THIS AREA THE MAXIMA IS TO PEAK AT 20-45MM BY
24-60 HRS...WITH LOCALLY HIGHER AMOUNTS HIGHLY LIKELY DUE TO
STRONG TOPOGRAPHICAL FORCING.

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

$$




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