Upcoming Weather Pattern Change Has Classic February La Niña Signature
Published: February 15, 2018
Mid- to late February will bring a weather pattern change that has La Niña's signature written across the United States.
La Niña typically brings colder-than-average conditions to the northwestern United States in winter while a ridge of high pressure holds strong in the western Atlantic and brings above-average temperatures to parts of the southern and eastern states.
(MORE: Winter Storm Central)
Forecast guidance depicts a pronounced reconfiguration of the jet stream during the second half of February to the pattern described above.
"Models are locking onto a common 'February La Niña pattern' for North America. This pattern brings cold weather for the western half of North America, with much-above-average warmth for the East," said Michael Ventrice, a meteorological scientist for The Weather Company, an IBM Business.
The latest 6- to 10-day temperature outlook (Feb. 20-24) from NOAA's Climate Prediction Center illustrates the expected overall temperature trend of a colder Northwest and a mild East.
It should be noted that even before this large-scale pattern change arrives, much of the East will see highs 10 to 30 degrees warmer than average through Friday before briefly cooling down again.
After a chilly weekend, temperatures next week could rise back into the 60s and possibly low 70s as far north as the mid-Atlantic early next week. Highs in the 60s, 70s and 80s are expected in the Southeast.
Meanwhile, the northern Plains will be frigid next week with highs in the single digits and teens.
(MORE: Extended Temperature Forecast)
Storm Track Fuels Potential Heavy Rain Threat and Wintry Weather
In between the dichotomy of temperatures expected mid- to late February is where the storm track associated with the jet stream is likely to set up across the central states.
The weather pattern across the Lower 48 in late February is expected to feature a southward dip in the jet stream over the West and ridge of high pressure in the South and East. In between, a potential battleground may set up where storm systems track along.
This could lead to periods of snow or a wintry mix in the colder air to the northwest of the storm track next week in the Midwest and Plains.
Bouts of rain and thunderstorms may affect parts of the South, mid-Mississippi Valley and Ohio Valley. If the rainfall moves over the same areas for multiple days, then flooding could potentially develop in parts of those regions next week.
(MORE: 7-Day Rain/Snow Forecast)
The southward dip in the jet stream across the West could also bring some needed snowpack to the Rockies.
(MORE: Heaviest Snow to Remain Anchored in the West Into Next Week)
Of course, it's far too soon to detail the magnitude of impacts for any storm systems that develop in the second half of February.
La Niña's Typical Temperature Influence Not Strong This Winter
La Niña is a periodic cooling of the eastern and central equatorial Pacific Ocean waters, which can influence weather patterns globally. This effect is most prevalent in the winter months for the Northern Hemisphere, where the United States is located.
The temperature pattern across the Lower 48 during this winter's La Niña event has not followed what is typically expected due to overriding factors in the atmosphere.
In the 90 days ending Feb. 10, temperatures had generally been below average in the East overall while above-average warmth had been prominent in the much of the West. For parts of the South, mid-Atlantic and Northwest, that is opposite of what we typically see when it comes to winter temperatures during La Niña events.
A year ago when La Niña conditions were also present in the equatorial Pacific Ocean, the temperature pattern in the U.S. was very similar to what is expected in mid- to late February this year.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.