2017–18 North American winter

2017–18 North American winter
Seasonal boundaries
Meteorological winter	December 1 – February 28
Astronomical winter	December 21 – March 20
Seasonal statistics
Total fatalities	Unknown
Total damage	Unknown

The 2017–18 North American winter refers to winter in North America across the continent from late 2017 through early 2018. While there is no well-agreed-upon date used to indicate the start of winter in the Northern Hemisphere, there are two definitions of winter which may be used. Based on the astronomical definition, winter began at the winter solstice, which in 2017 occurred on December 21, and ends at the March equinox, which in 2018 will occur on March 20. Based on the meteorological definition, the first day of winter is December 1 and the last day February 28. Both definitions involve a period of approximately three months, with some variability.

Seasonal forecasts

Temperature Outlook

Precipitation Outlook

On October 19, 2017, the National Oceanic and Atmospheric Administration's Climate Prediction Center released its U.S. Winter Outlook. The outlook noted a 55–65% chance that a La Niña would develop. According to CPC Deputy Director Mike Halpert, any such La Niña was expected to be "weak and potentially short-lived", but it could still affect the season. He also noted that La Niña years normally result in colder-than-average, wetter winters in the northern tier of the United States and the inverse conditions across the south. In terms of precipitation, wetter-than-average conditions were favored across the majority of the northern United States, including a region spanning from the northern Rocky Mountains to the eastern Great Lakes in addition to the Ohio Valley, Hawaii, and western and northern Alaska. Drier conditions were anticipated across the entire southern United States. Above-average temperatures were favored across the southern two-thirds of the contiguous United States and along the east coast, as well as in Hawaii and the northern and western parts of Alaska. The outlook favored below-average temperatures in the northern tier, from Minnesota to the Pacific Northwest region as well as southeastern Alaska. The remainder of the country was assigned equal chances of either above or below-normal temperatures or precipitation. The drought outlook noted that drought was likely to remain in parts of the northern Plains, with recovery likely to the west. The development of limited regions of drought was possible in regions that did not receive rainfall associated with tropical systems during the 2017 Atlantic hurricane season.

Seasonal summary

The month of November began with the highest snow extent in at least one and a half decades, with snow covering over a quarter of the contiguous United States, 22% more than the same date in 2011, the next-most-recent year with comparable snow coverage at that date. However, this trend did not last through all of the month, with the last week having the least snowfall of that time of year for the same time period.

Events

Early December winter storm

File:December 2017 Winter Storm.png

The snowstorm on December 8 as it was affecting the U.S. Gulf Coast.

The December 8 snowstorm in Fairmount, Georgia

A strong winter storm affected areas from northeastern Mexico to the Northeastern United States in early December. The origins of the storm were complex, with the initial disturbance forming over the extreme southern United States as a stationary front left behind from a departing extratropical cyclone on December 7. At the same time, a cold airmass was establishing itself into the Deep South. A large plume of moisture encompassed the entire Gulf Coast, and snow broke out early on December 8 in places that rarely even see snow, including Mexico, southeastern Texas and Louisiana – even in the Florida Panhandle. The storm dropped up to 25 inches (64 cm) of snow in some parts of the Southeast as it slowly moved eastwards, breaking several snowfall records; meanwhile, a gulf low formed in the Gulf of Mexico the same day – this would ultimately become the dominant low of the system. Transitioning into an extratropical cyclone off the east coast of the United States, the system began moving parallel to the shoreline, with a large swath of snowfall accompanying it. The low slowly deepened throughout the day of December 9, bringing the first snow of the season to many parts of the Northeast and New England.

Up to 400,000 people were left without power across the affected regions, several schools and roads shut down, and 3 were have confirmed to have been killed by the storm as of December 9.

Post-Christmas cold wave

In late December, a strong Arctic airmass came and established from Canada into the Midwestern and Northeastern United States with the core of the cold centered in the Upper Midwest, Interior Northeast, and Eastern Canada. Temperatures were 10 to 20 °F (−12 to −7 °C) below average for that time of year. International Falls, Minnesota recorded a record low temperature on December 27 of −32 °F (−36 °C).

The ball drop on the evening of December 31 into the morning of January 1 at Times Square in the Manhattan section of New York City is expected to be one of the coldest ball drops on record at midnight. Temperatures are expected to be in the low teens at around midnight in Times Square.

External links

• 2017 Storm Summaries from the Weather Prediction Center