Lably
Skip to content

February 15–20, 2021 North American winter storm

Category 3 winter storm and ice storm in the United States

  • 12 min read
  • 2 chapters
NASA satellite image of Winter Storm Viola over the Central United States on February 17, 2021. The winter storm brought additional wintry weather to the Southern U.S. only days after another severe w
NASA · Public domain

Related on Lably

Through Canada, Great Plains and Atmospheric pressure

The system resulted in over 170 million people being placed under winter weather alerts, stretching from the West Coast to the East Coast. Over 4 million people lost power due to the storm, particularly in areas of the Deep South and interior Southeast. The system worsened the 2021 Texas power crisis, causing additional major damage to the Texas power grid just days after the previous storm came through the area and hampering recovery efforts. It also contributed to a historic cold wave that affected most of the Central United States. In total, the winter storm resulted in at least 29 fatalities, with 23 in the United States and six in Mexico. The system is estimated to have caused at least $2 billion (2021 USD) in damages, mainly due to blackouts and structural damage. Excluding the winter storm a few days previous to this storm, the system was the costliest winter storm in the United States since the March 1–3, 2018 nor'easter, and the deadliest since the Blizzard of 2016.

Meteorological history

On February 15, a weakening extratropical cyclone in the Pacific Ocean began moving ashore in the Pacific Northwest, with the frontal system having a minimum central pressure of 1,001 mb (29.6 inHg). Precipitation bands began developing with the system in portions of the Pacific Northwest, as well as the Rocky Mountains by 21:00 UTC that day. The frontal system then pushed eastward, and by 18:00 UTC on February 16, the system was crossing the Rocky Mountains, and fronts connected several low-pressures areas associated with the storm from north to south. Simultaneously, the main center of low pressure spawned several other low-pressure areas, while the storm began organizing. On February 17, the system developed a new low off the coast of Texas. A combination of a large trough in place over the Central United States, a large polar airmass being channeled southward, and moisture from the Gulf of Mexico caused snow and freezing rain to fall over the Southern States. For the next couple of days, the storm moved eastward while becoming elongated, before moving off the East Coast of the U.S. on February 19. However, the storm stalled off the East Coast of the U.S. for another day, bringing additional precipitation to the region, before finally beginning to move out to sea on February 20.

The storm organized significantly and strengthened as it moved out into the Atlantic, with the storm's central pressure reaching 990 millibars (29 inHg) at 09:00 UTC on February 20. Afterward, the storm underwent explosive intensification, with the storm's central pressure dropping from 995 millibars (29.4 inHg) to a peak intensity of 948 millibars (28.0 inHg) from February 21 to 22, as the storm moved eastward across the North Atlantic. On February 22, the Free University of Berlin also gave the storm the name Dieter. Then, the cyclone gradually began to weaken, with the storm spawning a new low-pressure system to the northeast on February 24. Over the next couple of days, the storm rapidly weakened as it accelerated towards the northeast, before dissipating on February 26.

Sign in to keep reading

One more chapter is free with a Lably account.

More in Earth science