Accuweather is predicting big snows from the mid-Atlantic to southern New England this coming winter (2012-2013) (

In its winter outlook released today, it forecasts above average snowfall for major I-95 cities including Richmond, Washington, D.C., Baltimore, Philadelphia and New York City.

“The I-95 cities could get hit pretty good. It’s a matter of getting the cold to phase in with the huge systems that we are going to see coming out of the southern branch of the jet stream this year,” forecaster Paul Pastelok said.

But our team of winter weather experts and long range forecasters at the Capital Weather Gang (CWG) suggest Accuweather’s forecast amounts to a speculative guess, and is about as likely to be wrong as it is to be right.

The principal reason Accuweather favors big mid-Atlantic and I-95 snows is tied to its expectation of the development of a weak-to-moderate El Nino. A weak-to-moderate El Nino it says “feature[s] a strong southern branch of the jet stream across the U.S.” than can join up with the northern branch of the jet stream and produce big East Coast snow storms.

But CWG’s winter weather outlook lead author Matt Ross cautions it’s too early to predict the strength of the El Nino. Furthermore, he doesn’t think a weak-moderate El Nino guarantees big snow production even if it materializes.

“I believe a weaker event would not be as favorable for cold and snow in the D.C. area as Accuweather is suggesting,” Ross said.

Matt Rogers, who also specializes in long-range forecasting for CWG, said it’s important to recognize El Nino winter has produced widely varying snowfall totals in the region.

Feast or famine: snowfall amounts during El Nino years over the last few decades have tended to be either very high or very low (Matt Rogers)

While Rogers agrees with AccuWeather’s prediction for a weak-to-moderate El Nino, he stressed other factors play a big role in mid-Atlantic snowfall.

“El Niño winters can supply significant winter snow to the East Coast IF they are accompanied by bigger blocking patterns in the North Atlantic,” he said.

The blocking patterns Rogers mentions help establish cold air over eastern North America - critical for big storms to produce snow rather than rain. Specifically, he’s referring to the negative phases of the Arctic and North Atlantic Oscillation (AO and NAO).

If these phases are positive - like they were last winter - little snow may once again visit our region, said CWG winter weather expert Wes Junker.

“El Nino’s that have sustained periods with a positive AO and NAO generally are not snowy,” Junker said.

All things being equal - El Nino years average more snowfall (around 19 inches) than the 30-year average (14.5”) in D.C. Junker said. But after analyzing the data, he found only 50% percent of El Nino years since 1950 (20 seasons) have been snowier than normal.

Last year at this time, Accuweather’s Henry Margusity predicted ”near normal” snow along the I-95 corridor and above normal snow in the mountains. Most of this region experienced much below normal snow.

Junker’s response to Margusity’s prediction at the time was: “I think it’s too early to make any definitive call about snow or even what the winter will be like.”

CWG’s winter outlook will be issued in the fall.