South America Forecast Discussion - International Desks NWS Weather Prediction Center College Park MD 1152 AM EST Fri Mar 07 2025 GFS data at ftpprd.ncep.noaa.gov/data/nccf/com/gfs/prod/ South America Forecast Bulletin 7 Mar 2025 at 1700UTC: In the large scale, the Madden Julian Oscillation (MJO) is currently entering its phase 2, which is indicative of an increase in upper convergence across South America through the weekend. Note also that sea surface temperatures off the coast of Ecuador are above average, which may help motivate higher precipitation totals when atmospheric conditions are favorable. In Argentina, south Bolivia, and Paraguay, a feature of interest is a fast moving potent surface cold front impacting the region for the next three days. This front will support upper divergence throughout its lifespan. By late Friday evening, expect the cold front to develop across Buenos - Aires / La Pampa and Cuyo regions. At the low levels, the South American Low Level Jet (SALLJ) will continue to channel moisture to central South America and will lose definition by Saturday afternoon as the front progresses northward. From Friday morning through Saturday morning, these conditions will yield a total precipitation maxima of 35 - 70mm with a slight risk for severe weather across the Buenos Aires - La Pampa region, and a total precipitation maxima of 25 - 50mm in the Cordoba - Santa Fe region. By Saturday evening, this front will be across northeast Argentina and into south Brasil and will weaken thereafter. Moisture transport from the tropical regions will still be favorable, supporting a total precipitation maxima of 75 - 125mm across far north Argentina and south Bolivia with a marginal risk for severe weather from Saturday morning through Sunday morning. Also expect a total precipitation maxima of 25 - 50mm in Cordoba - Santa Fe for the same time period. Dry air advection will begin to dominate this region thereafter, leading to a subtle decrease in total precipitation maxima. In Mid - Latitude South America ... In Chile, a potent upper trough, with an axis at 26S 73W to 64S 61W, will exit into Argentina by Saturday morning. Expect the greatest chance for precipitation accumulations to be from Friday afternoon through the evening for Southern Chile. During this short window of time, mid - level vorticity advection and low level moisture convergence will be most favorable. These conditions will yield to a total precipitation maxima of 15 - 25mm. Another period of precipitation impact will be Sunday morning through Monday morning. Starting Sunday morning, a jet streak, with a center at 51S 92W, will begin to intensify and impact southern Chile by Sunday evening. Upper divergence will be most favorable from late - afternoon Sunday through the evening and will be accompanied by mid - level vorticity advection. Furthermore, in the low levels, a long fetch moisture plume and strong wind speeds, exceeding 45 knots, will help enhance moisture convergence and orographic effects across southern Chile. These conditions will yield to a total precipitation maxima of 25 - 50mm. In Tropical South America ... In the upper - levels, a semi - stationary loosely defined upper ridge will continue to affect the upper level regime across Peru and Bolivia for the next three days. On Friday afternoon, this ridge will have an axis at 19S 70W. To the east, an upper trough, with an axis at 15S 60W to 25S 56 on Friday afternoon, will become more defined and propagate east through the next three days. The interaction between these two features will favor weak speed divergence across east Bolivia and south Peru through Saturday afternoon. From Friday morning through Saturday morning, ample moisture convergence along a low level trough will favor a total precipitation maxima of 20 - 35mm in southeast Peru and northwest Bolivia. Elsewhere in Tropical South America, the ITCZ and NET will continue to be the main driving force for precipitation in the region for the next three days. A series of low level troughs accompanied by moisture convergence will support an increase in total precipitation maxima across east Brasil and the Amazon Basin. Another area of interest is west Ecuador, where from Saturday morning through Sunday morning when speed divergence and moisture convergence will be most favorable, yielding to a total precipitation maxima of 15 - 30mm. Tinoco - Morales...(WPC) Ledesma...(WPC)