A mild winter could be in store for much of the United States this winter, according to the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC). The most recent report indicates that in the U.S. Winter Outlook for December through February, above-average temperatures are most likely across the northern and western U.S., Alaska and Hawaii.
Additionally, El Niño has a 70 to 75 percent chance of developing. “We expect El Niño to be in place in late fall to early winter,” said Mike Halpert, deputy director of NOAA’s CPC. “Although a weak El Niño is expected, it may still influence the winter season by bringing wetter conditions across the southern United States, and warmer, drier conditions to parts of the North.”
Looking at the conditions, David Miskus, meteorologist with the CPC in College Park, MD, provided some insight to WLJ on drought conditions, saying the U.S. Drought Monitor as of Oct. 23 shows long-term drought remained in most of the Southwest from subnormal 2017-18 winter precipitation and warmth, especially in the Four Corners region and in the Northwest, especially Oregon. The Southwest drought was somewhat eased in the short-term by Pacific tropical moisture from tropical storms Rosa and Sergio which brought ample rains to most of Arizona and Utah. He noted that the 2018 Southwest monsoon (July, August, September) was mixed.
Miskus went on to say that, although this summer’s moisture was welcome and provided a nice start to this year’s water year in the Southwest, he told WLJ via email, “Many years of abnormal dryness and warmth has led to severe hydrologic drought (rivers, reservoirs, wells, ponds, subsoil moisture), and it will take a sustained time of above-normal precipitation (and lower temps would help) to make significant widespread recovery.”
In contrast, Miskus noted the late summer percent of normal precipitation in the Northwest was the opposite, with very dry and warm conditions experienced. Fortunately, last winter was close to normal, so the drought effects were more agriculturally-related (poor pastures, ranges, crops), although some streams and ponds did dry where last winter was also below normal.
With that said, Miskus told WLJ, “This winter’s outlook does point toward favorable odds of above-normal precipitation for the Southwest due to the expected development of a weak El Niño which tends to enhance the sub-tropical jet [stream] across the southern tier of states, usually bringing enhanced moisture and storm systems. But the El Niño moisture usually brings above-normal temperatures, so this moisture may fall as snow mainly in the highest elevations of the West.”
He went on, “Unfortunately, chances for subnormal precipitation and above-normal temperatures are favored in the Northwest, so this does not bode well after some of this region had a harsh summer. At least in the short term, some precipitation has fallen on the Northwest and provided some relief from this summer’s drought.”
Below is CPS’s summary of the 2018 U.S. Winter Outlook, which includes the months of December through February.
• Warmer-than-normal conditions are anticipated across much of the northern and western U.S., with the greatest likelihood in Alaska and from the Pacific Northwest to the Northern Plains.
• The Southeast, Tennessee Valley, Ohio Valley and Mid-Atlantic all have equal chances for below-, near- or above-average temperatures.
• No part of the U.S. is favored to have below-average temperatures.
• Wetter-than-average conditions are favored across the southern tier of the U.S., and up into the Mid-Atlantic. Northern Florida and southern Georgia have the greatest odds for above-average precipitation this winter.
• Drier-than-average conditions are most likely in parts of the northern Rockies and Northern Plains, as well as in the Great Lakes and northern Ohio Valley.
• Drought conditions are likely to persist across portions of the Southwest, Southern California, the central Great Basin, central Rockies, Northern Plains and portions of the interior Pacific Northwest.
• Drought conditions are anticipated to improve in areas throughout Arizona and New Mexico, southern sections of Utah and Colorado, the coastal Pacific Northwest and the Central Plains.
An explanation of predictions on NOAA’s website explains that the seasonal outlooks give the likelihood that temperatures and precipitation will be above-, near- or below-average, and how drought conditions are expected to change, but the outlook does not project seasonal snowfall accumulations. Snow forecasts are generally not predictable more than a week in advance. Even during a warmer-than-average winter, periods of cold temperatures and snowfall are still likely to occur.
NOAA’s CPC updates the three-month outlook each month. The next update will be available on Nov. 15. — WLJ