WITHIN a few months this could be a scene in America's widening war on drugs: It is 3 a.m. An 80-mile-an-hour racing-style cigarette boat rumbles along the darkened waters of the Banana River near Cape Canaveral, Fla. The long, sleek boat, running with lights out, carries a clandestine shipment of Colombian cocaine.
Lying in wait along the river are two state national guardsmen. Using special night-vision equipment, the soldiers have been monitoring traffic on the river for a month. Now, relying on intelligence data, they match the name and description of the cigarette boat with that of a known drug runner. The guardsmen radio nearby agents of the Drug Enforcement Administration, who swoop in by helicopter and make the arrest.
This scenario, though hypothetical, could become reality this summer as federal officials press hundreds of National Guard volunteers into service in the battle against illegal drugs.
Forty million dollars approved by Congress will go into a nationwide effort by the National Guard to slow the flow of drugs, especially along the Southern border.
``We are prepared and capable,'' says an official of the Florida National Guard.
``The National Guard has an important role'' in the drug fight, says Rep. Larry J. Hopkins (R) of Kentucky.
But Congressman Hopkins grumbles that the Pentagon let plans for using the guard ``gather dust for months'' before Congress prodded the generals in ``Fort Pentagon'' to get moving.
Since last year, states have submitted dozens of plans for using the National Guard to wage war against South American drug cartels, which are selling billions of dollars worth of narcotics in the United States.
Top priority will go to states along the nation's borders, as well as Puerto Rico, the Virgin Islands, and the District of Columbia. Florida, Texas, and California will spearhead much of the battle.
Other states considered in the front lines are Alabama, Arizona, Georgia, Hawaii, Louisiana, Mississippi, New Mexico, New York, Oregon, South Carolina, and Washington.
Yet interior states will also be critical. Kentucky, for example, will step up a joint National Guard/state police effort against home-grown marijuana, particularly in the mountainous eastern counties.
Last year, working together for only three weeks, Kentucky guardsmen and police used military helicopters to spot and destroy 436 marijuana plots containing 91,748 plants. This year, the joint effort will be expanded to 90 days, covering most of the summer growing season.
National guardsmen will be thrown into a nationwide struggle that has grown increasingly dangerous and where the rules are changing.
Several years ago, 80 to 90 percent of all cocaine smuggled into the US came aboard aircraft, most of them small, private planes. An estimated 18,000 illegal flights cross the US border every year, and many of those are drug carriers.
But in recent months, the game has changed. Today, perhaps only 40 percent of cocaine comes by air, while more and more shipments arrive by boat and truck.
The National Guard can help in the air war. But the largest boost to America's border defenses will be against smugglers using the highways from Mexico and from the nation's ports.
Currently, US Customs officials have the manpower to check only 5 to 10 percent of the cargo arriving aboard 58,000 commercial ships and aircraft annually. One official notes that even in the busy port of Miami, only six inspectors are available much of the time.
Customs concentrates on ships and planes from Latin America, source of most cocaine. But tons of the drug slip through.
When seagoing smugglers are caught, the haul is sometimes tremendous. In November 1987, agents found four tons of cocaine at Port Everglades, Fla., in containers of furniture that had been transshipped through Honduras. The following May, nearly as much cocaine was found at Tarpon Springs, Fla., in crates of furniture wood that had also come through Honduras.
In Florida, dozens of guardsmen are expected to join Customs officials opening crates from ships and air-cargo planes. Along the Texas border, they will be checking trucks from Mexico.
US Rep. Nicholas Mavroules (D) of Massachusetts, who strongly supports the use of military forces against the drug cartels, says: ``I feel the Southern border could be shut down within 18 months. But [the Pentagon] must make a commitment and change attitudes.''
An official with the Florida National Guard agrees that much could be done. He suggests that with some help from the regular Navy and Air Force, ``we could almost seal off the state. Sophisticated radar can tell us if there's even a rowboat out there.''