Prognostic Meteorological Discussion
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FXSA20 KWBC 121647
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1147 AM EST FRI FEB 12 2016

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

MODEL DISCUSSION (VALID FROM FEB 12 AT 0000 UTC): AT MID/UPPER
LEVELS...A HIGH AMPLITUDE TROUGH IS TO MOVE ACROSS THE SOUTHERN
CONE INTO CHILE ARGENTINA DURING THE NEXT 12-18 HRS. THE DEEP
TROUGH WILL SUSTAIN HEIGHT FALLS OF 75-150GPM ACROSS PATAGONIA-LA
PAMPA/SOUTHERN BUENOS AIRES IN ARGENTINA. THROUGH 42-48 HRS THE
TROUGH MOVES TO THE WESTERN ATLANTIC...TO MEANDER EAST ACROSS 40W
BY 72 HRS...AND ACROSS 25W/30W BY 96 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 24 HRS. BUILDING POLAR RIDGE IS TO QUICKLY
DISPLACE THIS FEATURE NORTH ACROSS RIO DE LA PLATA/URUGUAY-CORDOBA
TO MENDOZA IN ARGENTINA BY 42-48 HRS. AS IT ACCELERATES ACROSS
CENTRAL ARGENTINA THIS IS LIKELY TO TRIGGER A PREFRONTAL SQUALL
LINE AND SEVERE CONVECTION. THE FORECASTED HELICITY VALUES FOR
THIS EVENING/EARLY SATURDAY MORNING SHOW POSSIBLE MESOCYCLONES
DEVELOPING IN ASSOCIATION WITH THIS FEATURE. IN STRONG
MESO-SYNOPTIC FORCING...SMALL TO MEDIUM SIZE HAIL IS HIGHLY
PROBABLE. THE FRONT IS TO THEN MOVE TO SOUTHERN BRASIL-NORTHERN
ARGENTINA BY 72 HRS...WHERE IT IS TO REMAIN NEARLY STATIONARY
THROUGH 96-108 HRS. AS IT ENTERS SOUTHERN CHILE THIS WILL TRIGGER
SCATTERED CONVECTION WITH ACCUMULATION OF 10-15MM THROUGH 36 HRS.
ACROSS CENTRAL ARGENTINA...WITH BOUNDARY LAYER DEW POINT
TEMPERATURES OF 22-24C AND PRECIPITABLE WATER CONTENT OF NEARLY
50MM...THE SQUALL LINE WILL TRIGGER 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 48-60 HRS...AND 15-20MM/DAY BY 60-108 HRS.

AS THE POLAR TROUGH MIGRATES ACROSS THE SOUTHERN CONE...A
MID/UPPER LEVEL RIDGE IS TO THEN TAKE ITS PLACE. THE RIDGE IS TO
HOLD OVER THE EASTERN PACIFIC THROUGH 60-66 HRS. BY 72-96 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...SUSTAINING THE ADVECTION OF
SUBTROPICAL MOISTURE INTO SOUTHERN PORTIONS OF CHILE/PATAGONIA IN
ARGENTINA. AT LOW LEVELS THIS WILL BE ACCOMPANIED BY AN ELONGATED
FRONT THAT IS TO STRETCH ACROSS SOUTHERN CHILE/PATAGONIA IN
ARGENTINA. 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.
ACROSS CENTRAL ARGENTINA THIS IS TO THEN SUSTAIN CYCLOGENESIS
LATER IN THE CYCLE...WITH MODERATE TO HEAVY CONVECTION ON THE
CENTRAL PROVINCES TO RESULT IN RAINFALL AMOUNTS OF 25-50MM.

AT 200 HPA...A BROAD CELL OF THE SUBTROPICAL RIDGE IS TO REMAIN
DOMINANT FEATURE ACROSS MID SECTIONS OF SOUTH AMERICA...WHILE
ANCHORING ON A HIGH THAT IS 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. ACROSS AMAZONAS-SOUTHERN COLOMBIA-NORTHERN
PERU THE DAILY MAXIMA IS TO PEAK AT 15-20MM...WITH LOCALLY HIGHER
AMOUNTS ON DAY 04 WHEN THE MAXIMA INCREASES TO 20-35MM. ACROSS
WESTERN ECUADOR...MEANWHILE...THE DAILY MAXIMA IS TO PEAK AT
10-15MM/DAY...WITH MAXIMA OF 20-40MM EXPECTED ON DAY 02.

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

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