The 12Z ECM indicates a large area of stratospheric warming shifts from Eurasia/Siberia across Alaska and into the U.S. late in the 10-day forecast. ECM is the first model to identify and deliver an arctic air mass to the North-central U.S. on day-10.

Stratospheric warming is forecast to develop and expand in the polar region, the last third of January. In 16 days, the GFS indicates a powerful warming event taking place mostly on the Eurasia side of the North Pole. However, the stratosphere is still cold across the U.S. and eastern North America therefore the arctic air at ground level generated by this event is not easy to forecast by various dynamic models.

In a rare occurrence, the projected U.S. gas population weight HDD for January 2023 is warmer than the already verified DEC-22 value and projected FEB-23 forecast.

The 5-day outlook is mostly dry across the Argentina and far southeast Brazil drought region. Anomalous heat risk is high in Argentina only. In the medium-range, wet risk increases. Thundershower activity is more widespread across Southeast Brazil reaching Uruguay at times and also Paraguay into northern Argentina. However, the core drought zone in northeast/east Argentina is likely mostly dry and somewhat hotter than normal as drought worsens.