SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
332 PM EDT THU SEP 05 2024

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

SOUTH AMERICAN FORECAST BULLETIN FOR 05 SEP 2024 AT 1900 UTC:

A BROAD MID-UPPER TROUGH AMPLIFYING OVER THE BELLINGSHAUSEN SEA IS
MEANDERING NORTHWARD SLOWLY AND STIMULATING A TIGHTENING OF THE
PRESSURE GRADIENT ALONG 48S-55S. THIS IS INCREASING LOW-LEVEL WIND
SPEEDS ACROSS THE SOUTHERN CONE...WHICH WILL YIELD TO PROLONGED
PERIODS OF MOISTURE CONVERGENCE AND PRECIPITATION. A TRAIN OF
FRONTS ASSOCIATES WITH THIS GRADIENT...WHICH WILL HELP TO
HIGHLIGHT PERIODS OF PRECIPITATION. ON THURSDAY EXPECT MAXIMA OF
20-45MM IN SOUTHERN AYSEN AND MAGALLANES INCLUDING MOUNTAIN SNOW.
ON FRIDAY...EXPECT THE ARRIVAL OF A FRONTAL WAVE LATE IN THE DAY.
THIS WILL STIMULATE PRECIPITATION YIELDING TO MAXIMA OF 25-50MM IN
SOUTHERN AYSEN...INCLUDING MOUNTAIN SNOW. IN MAGALLANES EXPECT A
MIX OF RAIN AND SNOW AND MAXIMA GENERALLY UNDER 15MM. ON
SATURDAY...EXPECT A ROBUST FRONTAL WAVE TO ENTER THE DRAKE PASSAGE
DURING THE EVENING. NOTE THAT THIS SYSTEM IS EXPECTED TO BE
ACCOMPANIED BY STRONG 50KT+ BOUNDARY LAYER WINDS IN WESTERN
MAGALLANES. ALTHOUGH THE STRONGEST MOISTURE CONVERGENCE WILL
LIKELY REMAIN TO THE SOUTH OF THE CONTINENT...EXPECT STILL
MODERATE PRECIPITATION IN SOUTHERN AYSEN WHERE MAXIMA COULD REACH
THE 20-45MM RANGE. IN MAGALLANES...EXPECT A TRANSITION FROM A
RAIN/SNOW MIX EARLY TO ALL SNOW BY THE AFTERNOON/EVENING. EXPECT
POTENTIAL ACCUMULATION OF 15-25CM OF SNOW IN PORTIONS OF THE
DARWIN CORDILLERA...AND MUCH LIGHTER AMOUNTS IN LOW-LYING
LOCATIONS.

A FRONT IS WEAKENING ACROSS SOUTHEAST BRASIL ON THURSDAY. THIS
WILL STILL FAVOR PRECIPITATION IN EASTERN SANTA CATARINA/SAO PAULO
AS THE MOIST PLUME INTERACTS WITH THE DIVERGENT ENTRANCE OF AN
UPPER JET. EXPECT ISOLATED MAXIMA OF 15-25MM WITH A MARGINAL RISK
OF SEVERITY. ALSO IN ASSOCIATION WITH THIS FRONT...MOISTURE
CONVERGENCE IN WEST BRASIL/PERU IS PEAKING ON THURSDAY REGARDLESS
OF THE WEAKENING OF THE FRONTAL BOUNDARY. THIS WILL FAVOR MAXIMA
OF 15-30MM FROM NORTHERN BOLIVIA INTO SOUTHERN COLOMBIA.

IN MID-SECTIONS OF THE CONTINENT...UPPER JET DYNAMICS AND SHORT
WAVE PERTURBATIONS WILL STIMULATE A WEAK PROCESS OF FRONTOGENESIS
ON FRIDAY THROUGH SUNDAY. BY SATURDAY EVENING...EXPECT A
STATIONARY FRONT ACROSS RIO GRANDE DO SUL...FAR SOUTHERN
PARAGUAY...FORMOSA IN ARGENTINA. GIVEN THAT UPPER JET DYNAMICS
WILL LIKELY PEAK SOUTH OF THE BOUNDARY...EXPECT MOST PRECIPITATION
ORGANIZING IN NORTHERN URUGUAY AND SOUTHERN RIO GRANDE DO SUL...TO
FAVOR ISOLATED MAXIMA OF 20-35MM.

LOPEZ...(DMH-PARAGUAY)
GALVEZ...(WPC)
TINOCO...(WPC)
LEDESMA...(WPC)