South American Pattern Unchanged; Argentina Stays Dry Through Dec 16th: The midday GFS includes potentially better rainfall in Argentina beyond Dec 15th, but confidence so far out is low – and other forecasting models so far do not include this change. In the meantime, continued dryness and warming temps are offered to Argentina the southern third of Brazil. And as La Nina strengthens, the market will have a closer eye on soil moisture there moving forward. The USDA’s latest vegetation health index compared to last year is attached. Only pockets of Argentina are at/better than last year, and these pockets exist largely on the fringe of Argentina’s main ag crop belt.
Normal to above normal precip will persist across Mato Grosso, Goias and Minas Gerais, where vegetation health continues to improve. However, drought in far S Brazil looks to expand a bit northward over the next 10 days, and some 40-45% of Brazil’s soy crop is at risk. Better rainfall is required here and across Argentina, but is unlikely to develop amid La Nina’s untimely arrival.
US Forecast Maintains Cool/Dry Pattern into Late December: A rapid shift to much colder temps has been established across the Northern & Western US, and this Canadian air mass work eastward in the next 24 hours. The 10-day forecast this evening is still marked by a stable deep low pressure Trough sinking into the Plains and Midwest into the second half of December, and this will act to sustain a cool, dry pattern through the period. The GFS model’s week 1 (top) and week 2 temp outlook is attached.
Overnight lows beginning Tues/Wed will range in the single digits and teens across the N Plains and N Midwest. By Dec 8th freezing lows will be spread across the nearly the whole of the Central, and bitterly cold temps moving forward will favor the N and E Midwest. Little precip of note is include, and any moisture that does fall will in the next 10-12 days will be isolated to Gulf and Southeast.
Warmer temps are likely beginning late month, but there’s not any indication of a wetter pattern developing across the Plains.