Models Remain in Poor Agreement in S America; Argentine Dryness Favored: The EU & GFS models as of this evening can’t even agree on the 5-day forecast, much less on South America’s pattern thereafter. The GFS maintains soaking rainfall in Cordoba & Santa Fe – both major producing states – while the EU models includes very little rain in Argentina over the next 10 days. This is an important difference, as recall low soil moisture reserves more easily allow for bouts of excessive heat, and January’s temp profile in Argentina will be impacted by late December precip. The EU model’s two-week temp anomaly forecast is at left, and ARC favors the EU model based on its performance so far in 2017.
Notice also that a relatively drier period lies ahead for Northern Brazil. This is not an issue in the near term, as sunlight is needed there. However, it appears that a longer term trend of declining soil moisture will stay intact in Argentina. And the Aussie bureau of meteorology this week has confirmed La Nina’s existence through the first quarter of 2018.
Snow Cover Raised Slightly for Northern Plains; Forecast Otherwise Unchanged: A bit more snow will fall across NE, ND and MN prior to next week’s cold event, but otherwise the 10-day forecast is little changed. Meaningful precip will continue to favor the Southeastern US and far E Midwest. Dry weather persists elsewhere.
The US climate into Jan 5th will be dominated by a swirling low pressure Trough aloft Eastern Canada. This Trough will at times force much colder Arctic air into the Plains and Midwest. The near term temp forecast has trended just a bit warmer, but beginning next Tues/Wed, overnight lows in the single digits will be common; lows across the Dakotas and MN will be well below zero. Snow cover will be abundant in IL, IN and OH, but scarce elsewhere. And a westward migration in meaningful precip is unlikely in the next two weeks. Expect the Drought Monitor to show worsening conditions across the Plains.