After an unusually mild winter across the nation, forecasters are now calling for a substantially warmer-than-normal spring.
The National Weather Service’s outlook, released Thursday, conveyed the same message: “No part of the country is favored to experience below-average temperatures this spring.”
The Weather Company’s outlook for April through June, issued March 12, is headlined: “Widespread Warmth Across U.S.”
Hues of orange, signaling various degrees of anomalous warmth, cover the maps released by these three organizations. While they agree most of the nation, if not its entirety, will be warmer than average, they do differ in region-to-region predictions.
The Weather Service and AccuWeather both forecast the strongest warm signal in the eastern United States and along the West Coast, with a weaker signal in the middle of the nation.
The Weather Company’s outlook, however, calls for the greatest chance of above-normal temperatures from the West Coast through the Midwest.
The forecast for a warm spring, the Weather Company’s outlook said, is in part due to the abnormally strong polar vortex, which has bottled up frigid air over the Arctic rather than allowing it to spill south. The vortex typically breaks down in early spring.
The Weather Company’s chief meteorologist, Todd Crawford, also noted in the outlook that cooling ocean temperatures in the tropical Pacific often support warmer-than-normal conditions heading into summer over the Lower 48 states.
Matt Rogers, a long-range forecaster for the Commodity Weather Group and a Capital Weather Gang contributor, said he agreed with the general idea of a warm spring across the nation but cautioned the West may see average to cooler than average conditions due to the continuation of a stormy pattern that has recently brought beneficial rain and snow to California.
Rogers also said there are signs the polar vortex is weakening, which could allow for some cooler weather in the central and eastern United States in the coming weeks.
“I agree with them [the other outlooks] in spirit overall, but I do need to think we need to watch for some cooler volatility during the front half of April,” Rogers said.
The forecast for warmer-than-average weather in the coming months follows a winter that ranked as the sixth-warmest on record for the Lower 48 and a premature start to spring in many areas. According to the USA National Phenology Network, which tracks the blooming of plants, leaves emerged on trees three to four weeks early in parts of the southern and eastern United States.
While factors such as the strength of the polar vortex and ocean and atmosphere cycles, such as El Niño, play a large role in a given season’s weather, the long-term increase in average temperatures due to human-caused climate change are increasing the likelihood of abnormal warmth.
There is a relatively remote possibility that the warmer than average spring into the early summer could help slow the spread of coronavirus, if some preliminary analyses that have found or projected drops in virus transmission at higher temperatures, prove correct. However, these analyses have not been peer-reviewed, and the virus has been spreading in parts of the United States that have warm weather, including Florida, as well as warm international areas, including the Philippines. In recent days, the virus has also made inroads in South Africa and India, two countries with mild average temperatures.
Andrew Freedman contributed reporting.