093
FXSA20 KWBC 071652
PMDSA
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)
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