The early blast of winter this month could be followed by three months of warmer-than-normal temperatures, if this winter follows a progression similar to that of 2002-2003.

The cold October so far this year is similar to a record cold October in 2002, which was followed by a warm, dry November through January that winter, said Lee Czepyha, lead forecaster with the National Weather Service office in Rapid City.

October 2002 was the coldest October on record at Rapid City Regional Airport.

This October, temperatures at Rapid City Regional Airport through Sunday have been running 17.6 degrees below normal for the month. At the NWS office in Rapid City, temperatures have been 19 degrees below normal.

The average high in Rapid City so far in October has been 41.7 degrees, compared with the normal low of 41 for Oct. 12, Czepyha said.

The good news is that the early cold snap is part of a weather pattern similar to that of fall 2002, when a moderate El Nino in the equatorial Pacific Ocean was offset by a longer-lived El Nino-like pattern of northern Pacific variability.

That second pattern, called a Pacific Decadal Oscillation (PDO), was in a negative phase, having shifted from a positive phase in the late 1990s, according to the NWS web site.

That combination of patterns is in place again, Czepyha said.

The result is a forecast for slightly above-average temperatures across western South Dakota and northeastern Wyoming, especially from mid-November to mid-January, Czepyha said. However, occasional strong intrusions of arctic air are possible, especially in February and on the plains of western South Dakota.

"The cold we're having now will break in the next couple of weeks, and we'll go into a drier, warmer stretch for a few months," Czepyha said.

The pattern also indicates near-average precipitation for November through January, although it could be slightly below average because of the forecast of warmer temperatures.

In any case, the November through February period is always dry, averaging about 1.5 to 2.5 inches of moisture, only about 10 percent of the annual average, Czepyha said.

The cold weather this month isn't the only similarity with 2002. That year, like this year, August was cool and September was warmer than normal, Czepyha said.

Precipitation from November through January of 2002-03 was below normal, but it was about normal for March and April of 2003, Czepyha said.

The El Nino/PDO pattern is not an indicator one way or another of late spring storms, he said.

"In April and May, they just happen," Czepyha said.

Meanwhile, this week will see a slow warming trend with a chance of snow Tuesday morning, then rain and a high near 38 in the afternoon.

The area could see more snow and freezing rain Wednesday morning, and a high near 47.

The forecast calls for a clearing to partly sunny skies on Thursday with a high in the low 50s.

Contact Steve Miller at 394-8415 or steve.miller@rapidcityjournal.com.