963
FXSA20 KWBC 281857
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT MON OCT 28 2024
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 28 OCT 2024 AT 1900 UTC: AN
AMPLE MID-UPPER RIDGE EXTENDS OVER THE EASTERN PACIFIC FROM ABOUT
25S SOUTH INTO 42-45S AND ALONG 85W 95W. THE SOUTHWARD
AMPLIFICATION OF THIS RIDGE IS FAVORING A TIGHTENING OF THE
GRADIENT ALONG 50S-55S...YIELDING TO THE FORMATION OF A
ZONALLY-ORIENTED UPPER JET IN THE REGION. AS THE JET IS EXPECTED
TO HOLD THROUGH THE FORECAST CYCLE...EXPECT PERTURBATIONS TO CROSS
THE CONTINENT GENERALLY TO THE SOUTH OF 50S...YIELDING TO
SCATTERED PRECIPITATION IN AREAS TO THE SOUTH OF 48S IN AUSTRAL
CHILE. THROUGH EARLY TUESDAY...EXPECT MAXIMA OF 20-40MM FROM
SOUTHERN AYSEN INTO MAGALLANES. BY TUESDAY THROUGH EARLY
WEDNESDAY...A PEAK IN PRECIPITABLE WATER WILL FAVOR A PEAK IN
RAINFALL AMOUNTS...WHICH ARE FORECAST TO REACH MAXIMA OF 35-70MM.
ON WEDNESDAY...EXPECT THE WINDS TO ACQUIRE A NORTHWESTERLY
COMPONENT...WHICH WILL DECREASE THE POTENTIAL FOR MOISTURE
CONVERGENCE...YIELDING TO A MAXIMA OF 20-35MM.
A MID-UPPER TROUGH EXTENDS ALONG 90-91W IN THE EASTERN PACIFIC AND
IS FORECAST TO SLOWLY MEANDER TOWARDS THE CONTINENT WHILE LOSING
AMPLITUDE. THIS TROUGH IS FORECAST TO CROSS THE ANDES OF SOUTHERN
CHILE DURING WEDNESDAY...CROSSING PATAGONIA THROUGH THURSDAY
MORNING. ALTHOUGH MOISTURE WILL BE LIMITED WITH THIS SYSTEM WEST
OF THE ANDES...A DEVELOPING NORTHERLY LOW-LEVEL JET ALONG THE
EASTERN SLOPES OF THE ARGENTINEAN ANDES WILL BUILD PRECIPITABLE
WATER VALUES EXCEEDING 30-35MM IN NORTHERN PATAGONIA BY WEDNESDAY.
AS THE UPPER TROUGH ENCOUNTERS THIS AIR MASS...EXPECT THE
DEVELOPMENT OF A FEW THUNDERSTORMS IN NORTHERN PATAGONIA AND LA
PAMPA/SAN LUIS ON WEDNESDAY CAPABLE OF PRODUCING MAXIMA OF
15-20MM/DAY AND INCLUDING A SLIGHT RISK FOR SEVERITY.
THE SUBTROPICAL UPPER RIDGE/BOLIVIAN HIGH IS GAINING STRUCTURE IN
CENTRAL PORTIONS OF THE CONTINENT...WHILE EXTENDING AN AXIS FROM
EASTERN PERU/NORTHERN BOLIVIA INTO NORTHERN MINAS GERAIS/ESPIRITO
SANTO. MODELS AGREE ON THE RIDGE STRENGTHENING BY TUESDAY WHILE
RELOCATING TO SOUTHERN PERU. IN THE MEANTIME...SOUTHWESTERLY
MID-UPPER FLOW TO THE SOUTHEAST OF THE HIGH WILL AID WITH THE
AMPLIFICATION OF AN UPPER TROUGH ACROSS SOUTHEAST BRASIL BY
TUESDAY INTO WEDNESDAY/THURSDAY. THIS WILL YIELD TO AN INCREASE IN
VENTILATION IN EXTENSIVE AREAS OF CENTRAL AND EASTERN/SOUTHEAST
BRASIL BY MID-WEEK. IN THE LOWER LEVELS...MODELS ARE HINTING THE
POTENTIAL FORMATION OF THE SOUTH ATLANTIC CONVERGENCE ZONE (SACZ)
ON WEDNESDAY AND THURSDAY...EXTENDING FROM ESPIRITO SANTO INTO
RONDONIA/EASTERN BOLIVIA. HOWEVER...THE EXPECTED 850 AND 700 HPA
TROUGH IS NOT WELL DEFINED IN MODEL SOLUTIONS...AND ITS DURATION
IS LIMITED TO LESS THAN 48 HOURS. ACCORDINGLY...THE SACZ IS NOT
REFLECTED IN OUR FORECAST CHARTS...BUT MODERATE PRECIPITATION
AMOUNTS ARE. ON MONDAY...EXPECT THE HEAVIEST PRECIPITATION FROM
SOUTHERN MINAS GERAIS INTO SOUTHERN MATO GROSSO WHERE DIURNAL
CONVECTION WILL FAVOR 15-20MM/DAY AND MAXIMA OF 30-60MM...AND IN
ESPIRITO SANTO EXPECT MAXIMA OF 20-45MM. ON TUESDAY...EXPECT
MAXIMA OF 30-60MM IN ESPIRITO SANTO AND EASTERN MINAS
GERAIS...WHILE FROM CENTRAL MINAS GERAIS INTO EASTERN BOLIVIA
EXPECT MAXIMA OF 20-35MM. ON WEDNESDAY EXPECT MAXIMA OF 30-60MM IN
COASTAL LOCATIONS OF NORTHERN ESPIRITO SANTO/SOUTHERN BAHIA...AND
IN MATO GROSSO/SOUTHERN PARA IN CENTRAL BRASIL.
ENHANCED MOIST EASTERLY FLOW IN THE LOWER TROPOSPHERE IS
HIGHLIGHTING MOISTURE CONVERGENCE ALONG THE EASTERN SLOPES OF THE
EQUATORIAL ANDES IN ECUADOR...NORTHERN PERU AND SOUTHERN COLOMBIA
ON MONDAY. ALTHOUGH THE ATMOSPHERE IS ALREADY
STABILIZING...CONTINUED MOIST EASTERLY FLOW WILL LIKELY EXTEND THE
PERIOD OF MODERATE TO LOCALLY HEAVY PRECIPITATION THROUGH EARLY
TUESDAY. EXPECT 15-30MM/DAY AND MAXIMA OF 40-80MM IN EASTERN
ECUADOR AND NORTHERN PERU...WHILE IN CENTRAL PERU EXPECT MAXIMA OF
20-40MM. ACCUMULATIONS DECREASE THEREAFTER.
ACTIVE DIURNAL CONVECTION IS EXPECTED IN THE BOLIVIAN AND PERUVIAN
ALTIPLANO/ANDES ON A DAILY BASIS. UNDER THE INFLUENCE OF
VENTILATION FROM THE BOLIVIAN HIGH AND SUFFICIENT AVAILABLE
MOISTURE...EXPECT AMOUNTS OF 05-10MM/DAY AND ISOLATED MAXIMA OF
15-20MM ON A DAILY BASIS...ALTHOUGH ISOLATED HIGHER AMOUNTS ARE
POSSIBLE.
GALVEZ...(WPC)
ALAMO...(WPC)
LOPEZ...(DMH-PARAGUAY)
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