Prognostic Meteorological Discussion
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000
FXSA20 KWBC 111642
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1142 AM EST THU FEB 11 2016

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

MODEL DISCUSSION (VALID FROM FEB 11 AT 0000 UTC): UNDER INFLUENCE
OF A HIGH AMPLITUDE MID LEVEL RIDGE TO THE WEST...A POLAR TROUGH
IS FORECAST TO AMPLIFY ACROSS THE SOUTHERN CONE THROUGH 36-42 HRS.
AS IT PULLS ACROSS CHILE TO ARGENTINA THIS WILL SUSTAIN HEIGHT
FALLS OF 75-150GPM. IT IS TO THEN ENVELOP THE SOUTHERN
CONE/WESTERN ATLANTIC BY 60-84 HRS. THE TROUGH IS THEN FORECAST TO
SLOWLY MIGRATE ACROSS THE SOUTH ATLANTIC...NEARING 35W BY 96
HRS...AND 20W BY 120 HRS. AS IT PULLS ACROSS THE CONTINENT A
SUBTROPICAL JET MAXIMA IS TO ROUND THE BASE OF THE LONG WAVE
TROUGH...FAVORING AN UPPER DIVERGENT PATTERN ACROSS CENTRAL
ARGENTINA THAT IS TO VENT ORGANIZED DEEP CONVECTION. AT LOW LEVELS
THE ASSOCIATED FRONT PULLS ACROSS PATAGONIA TO LA PAMPA IN
ARGENTINA THROUGH 42-48 HRS. BUILDING RIDGE IS TO THEN DISPLACE
THIS FEATURE NORTH ACROSS RIO DE LA PLATA/ URUGUAY-CORDOBA TO
MENDOZA IN ARGENTINA BY 66-72 HRS...WITH A PREFRONTAL SQUALL LINE
TO LIKELY DEVELOP AS THE FRONT SURGES ACROSS ARGENTINA. DURING
THAT PERIOD ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR SEVERE
WEATHER TO DEVELOP...WITH FORECASTED HELICITY SUGGESTING
POSSIBILITY OF MESOCYCLONE FORMATION EARLY ON SATURDAY MORNING.
SMALL TO MEDIUM SIZE HAIL IS HIGHLY PROBABLE. THE FRONT IS TO THEN
MOVE TO SOUTHERN BRASIL-NORTHERN ARGENTINA WHERE IT IS TO REMAIN
NEARLY STATIONARY THROUGH 120-132 HRS. AS IT ENTERS SOUTHERN CHILE
THIS WILL TRIGGER SCATTERED CONVECTION WITH ACCUMULATION OF
15-20MM BY 24-48 HRS. ACROSS CENTRAL ARGENTINA/RIO DE LA
PLATA...THE SQUALL LINE WILL SUSTAIN RAINFALL MAXIMA OF
40-80MM...WITH LOCALLY HIGHER AMOUNTS POSSIBLE. OVER
URUGUAY-SOUTHERN BRASIL-MESOPOTAMIA VALLEY THIS IS TO THEN FAVOR
MAXIMA OF 25-50MM THROUGH 72-84 HRS...AND 15-20MM/DAY BY 84-132
HRS.

AS THE POLAR TROUGH MIGRATES ACROSS THE SOUTHERN CONE...A
MID/UPPER LEVEL RIDGE IS TO TAKE ITS PLACE. THE RIDGE IS TO HOLD
OVER THE EASTERN PACIFIC THROUGH 84-90 HRS. BY 96-120 HRS IT WILL
RAPIDLY ERODE AS AN AMPLIFYING POLAR TROUGH SURGES ACROSS THE
SOUTHEAST PACIFIC TO CHILE/ARGENTINA. THE DEEPENING TROUGH IS TO
ESTABLISH A SUBTROPICAL CONNECTION...FAVORING ADVECTION OF
SUBTROPICAL MOISTURE INTO SOUTHERN PORTIONS OF CHILE/PATAGONIA IN
ARGENTINA. AT LOW LEVELS THIS WILL BE ACCOMPANIED BY AN ELONGATED
FRONT THAT MOVES INTO SOUTHERN CHILE/PATAGONIA BY 96-120 HRS.
STRONG BOUNDARY LAYER WINDS OF 35-50KT ARE TO ACCOMPANY THIS
BOUNDARY AS IT ENTERS THE SOUTHERN CONE...TO ENHANCE LOW LEVEL
MOISTURE CONVERGENCE AND TOPOGRAPHICAL EFFECTS ACROSS SOUTHERN
CHILE. THIS WILL RESULT IN SCATTERED CONVECTION...WITH MAXIMA
EXPECTED TO RANGE BETWEEN 20-30MM. HIGHER AMOUNTS ARE HIGHLY
LIKELY ON THE OFFSHORE ISLANDS OFF THE COAST OF CHILE.

NORTH OVER THE CONTINENT...AT 200 HPA...BROAD CELL OF THE
SUBTROPICAL RIDGE IS TO REMAIN DOMINANT FEATURE ACROSS MID
SECTIONS OF SOUTH AMERICA DURING THE NEXT FIVE DAYS. THE RIDGE IS
TO ANCHOR ON A CLOSED HIGH FORECAST TO MEANDER BETWEEN CHACO
PARAGUAYO-NORTHWEST ARGENTINA AND SOUTHERN BOLIVIA. AN ELONGATED
TROUGH TO THE NORTH...MEANWHILE...IS TO EXTEND WEST ACROSS
NORTHERN BRASIL BETWEEN 10S-00N. THE TROUGH ALOFT...IN INTERACTION
WITH THE NEAR EQUATORIAL TROUGH...WILL VENT DIURNAL CONVECTION
ACROSS NORTHERN BRASIL...WHERE THE DAILY MAXIMA IS FORECAST TO
PEAK AT 10-15MM/DAY. HIGHER AMOUNTS ARE EXPECTED ACROSS SOUTHERN
COLOMBIA-NORTHERN PERU TO EASTERN ECUADOR WHERE THE MAXIMA IS TO
PEAK AT 20-45MM THROUGH 36 HRS. IT THEN DECREASES TO
10-15MM/DAY...SURGING ONCE AGAIN LATER IN THE CYCLE.
FURTHERMORE...UNDER INFLUENCE OF A NORTHERN HEMISPHERE TRADE WIND
SURGE OVER THE EASTERN PACIFIC...EXPECTING ENHANCEMENT OF LOW
LEVEL CONVERGENT PATTERN ACROSS WESTERN ECUADOR. THIS IS TO FAVOR
RAINFALL MAXIMA OF 40-80MM WITH POTENTIAL FOR LOCALLY HIGHER
AMOUNTS. OVER SOUTHERN PERU-ALTIPLANO EXPECTING SCATTERED
CONVECTION TO SUSTAIN DAILY MAXIMA OF 15-20MM. THROUGH 72-96 HRS
THIS INCREASES TO 20-35MM IN RESPONSE TO EVOLVING POLAR TROUGH
PATTERN OVER ARGENTINA.

LOPEZ...SMN (ARGENTINA)
ENRIQUEZ...DGAC (ECUADOR)
GALVEZ/DAVISON...WPC (USA)

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