During the past week or so an excessive rainfall event emerged in the East-Central/Mid-South U.S. The excessive rainfall event was caused by the combination of Madden Julian oscillation and subsurface Kelvin Wave moving across the tropical East Pacific. There are concerns of another such event evolving for early calendar springtime.

Combination of widening western snow cover and attendant arctic air held in place by the negative phase of the Pacific North America pattern joins forces with a developing negative phase of the North Atlantic oscillation flipping the record warmth in the East to colder than normal in 10+ days. The -PNA/-NAO combination push the Lower 48 States to colder than normal in 15 days.

Weak La Nina continues but a recent (warm) subsurface Kelvin Wave into the East Pacific has eroded the cool water supply to sustain La Nina. Near the Dateline the next Kelvin Wave is forming and by April shifts into the eastern equatorial Pacific wiping out La Nina.

The warm phase of the Pacific decadal oscillation is re-emerging. Coupled with an expected warmer than normal North Atlantic during the northern hemisphere warm season in 2018 research by McCabe, Palecki and Betancourt have shown a climatological increased risk of drought to the Northwest U.S., Great Plains and Southeast U.S. given these middle latitude oceanic conditions.