Autumn's frosty nights and rising winds bring more than a confetti of yellow leaves breaking loose from tightening branches. They also bring about the fall turnover on lakes. For the largemouth bass angler it's one of the highlights of the fishing year.

During summer, low winds and intense heat stratify lakes into three distinct layers -- the upper (epilimnion), middle (thermocline) and lower (hypolimnion). The upper layer is hot and lacks sufficient oxygen for gamefish. The lower layer stays cool enough for bass, but it, too, often lacks oxygen. The thermocline, usually 15 to 35 feet deep, is the place where big bass hang out from June through late September in area lakes.

Expert structure anglers find quality sport throughout the dog days by locating cover in mid-lake holes that lie in this comfort zone. For the average plug-tosser, however, things are decidedly tough during summer.

With the fall turnover, all that changes. No longer do you have to search for the thermocline and then seek out old mossback in some Stygian hole a mile from shore.

Recent chilly nights have cooled the surfaces of area lakes, and rising winds have blown the chilled water towards shore. This marks the beginning of the fall over turn. Since cold water is heavier than warm, the top cooled layer sinks as it reaches the shore. The lower, warmer waters are forced up and cooled in turn. It's a gradual process, eventually mixing all three layers of the lake to make them the same temperature.

Once the fall overturn is complete, all of the lake will be in comfortable ranges for bass. But since lake edges offer extensive cover, this is where largemouths will gravitate. If you like plugging the banks, rather than the tedious sport of studying depth-finders, thermometers and topomaps to find deep mid-lake bass sanctuaries, now's the time to hit the water. The next month to six weeks should yield excellent bank-fishing.

Campbell Edenton, of Lake Anna's Sturgeon Creek Marina, is no stranger to fall turnover. Last week, guide Bill Mathias and another angler returned to Campbell's dock as darkness clutched its fingers around the lake and squeezed the last drop of light out of the Piedmont Virginia day. The pair was not a little proud of the six bass thrashing in their live well, all running two to 5 1/2 pounds.

"That's nothing," said Edenton. "Come back in October. You'll see some stringers of eight bass weighting 40 pounds. Now only the pros like Bill can catch bass. When fall's feed starts, everybody can catch fish."

If your lunker sticks have been gathering dust since the largemouths gravitated offshore in June, now's the time to break them out, oil up the reels and spool fresh mono. Already the water temperature on Anna has fallen five to ten degrees from summer levels. The turnover is beginning. On all area lakes bass are moving up onto cover closer to shore and feeding more avidly by the day.

Edenton predicts early October for the onslaught of fall's major feed on Anna. Mathias thinks it will be a bit later, judging by records from his past season, probably starting in mid-October and running through early November. Only the weather will decide for sure; but already things are clicking.

Further north, in smaller lakes such as Occoquan, Brittle, Burke and Manassas, plus Maryland's Triadelphia, Rocky Gorge and Liberty, shoreline bassing is even further ahead. Hefty catches are coming to bank lure-tossers.

On tidal sections of rivers, where excellent bass fishing occurs around Washington, the fall turnover isn't as important: River currents and tides tend to mix the water throughout the year, preventing distinct stratification. However, the cooling water temperatures do instill a fresh intensity to the feeding of bass in such tidal flowages as the Potomac, Susquehanna, Rappahannock, Sassafrass, Choptank, Nanticoke and Chickahominy. The fish not only move into shallower water but often feed lustily throughout the entire day at this time of year.

If you pounded the shoreline during summer, all you tussled with probably were fiedgling bass. Light tackle worked fine for these welterweights. Not so for fall's sport. Bruisers will be cruising the banks from now on, and anything less than eight-pound test line is unwise. Ten is better still, and 12 isn't overkill.

Even though fall bass are hungrier and eager to lay on fat to tide them over winter, they still can be temperamental: Stock a variety of baits for autumn outings. Topping the list, according to bass guide Mathias, are crankbaits in the new naturalized finishes.

Spinnerbaits are his second choice for fall shoreline action. Buzz them on the surface, work them more slowly just under the top, or inch them across the bottom. If these approaches don't work, bass angler Ranny Isenberg, who works the lakes around Manassas, suggests fishing these lures on the "drop." Throw the spinnerbait out and watch for a strike as the lure sinks. If a hit doesn't come, reel in until the lure climbs near the surface, then let it drop again. Always be alert for a twitch of the line that spells a striking bigmouth.

Early and late in the day, topwater plugs such as Jitterbugs, Devil's Horses, and Tiny Torpedos, can draw rousing greetings from an angered bass. Try twitching them gently and also working them at a fast, "exciter" pace.

If the bass still prove elusive after this arsenal, switch to the old standby, the plastic worm. It's slower and more tedious, but when active lures won't produce, these silent sinkers will almost always draw enough action to salvage the day.