Kevin Myatt is The Roanoke Times' weather columnist.

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Our first springlike week is ending with rain. It may be heavy with some thunder tonight.

Is a soaking spring in store for Southwest Virginia? El Nino, which is still going strong, is one factor that may have some say in that.

El Nino is the recurring warming of a streak of central Pacific sea surface temperatures near the equator from northern South America westward. El Nino does not recur in regular cycles, but rather for periods of several months every few years, usually beginning in summer, peaking in winter, and fading by the following summer.

El Nino typically has the effect of intensifying the southern, or subtropical, branch of the jet stream that brings wet storms off the Pacific across the southern United States and toward our part of the country.

In winter, that usually means lots of rain, and when other factors can push the cold air southward, lots of snow. We know all about that in 2009-10.

El Nino's effects continue into spring, with the potential for vigorous storm systems to keep crossing the nation toward us, carrying Pacific moisture and sweeping in gobs of Gulf of Mexico moisture. We are seeing that this week, with our rainy weather and the first significant severe weather episodes in the southern Plains and lower Mississippi River valley regions to our west.

But the transition from winter to spring often results in the southern branch of the jet stream taking precedence over the colder branch from the north, regardless of the sea surface temperatures in the Pacific.

So even in many years without an El Nino, there is an increase in mild, wet storms arriving from the west by March or April.

El Nino's effects on spring, therefore, are often not as extreme or obvious as they are on winter. Except in unusually dry patterns, April showers tend to happen, El Nino or not.

The last three El Nino years have had contrasting spring results:

An extremely wet and mostly mild winter in 1997-1998 during the strongest El Nino on record was followed by a spring with somewhat above normal rainfall -- within 2 inches of normal -- in March, April and May.

A moderately snowy winter during a dying El Nino in 2002-2003 was followed by heavy spring rains, including Roanoke's May record of 10.11 inches.

The oddly dry winter of 2006-07, with below normal precipitation as most of the El Nino-charged wet storms were deflected into the central U.S., was followed by below normal rains in the spring, starting the slide toward prolonged drought that was not fully broken until last year.

Since we've already seen storm systems move through almost every week since early November, there probably will be no substantial change or increase as we enter spring.

The odds slightly favor a somewhat wetter than normal spring, but a record soaker isn't likely. Changes in short-term weather patterns will be more crucial in determining just how wet it gets rather than the occurrence of El Nino.

El Nino usually diminishes by late spring or early summer. Computer model data indicate this is likely to happen in the upcoming months. Whether it will be replaced by neutral conditions in the central Pacific or its alter ego, the cold-water La Nina, will be a major factor in weather patterns that will occur next fall and winter.

But let's take it one season at a time.