The wintriest days of winter in these parts come when the winds swing northwest and whip along on great sheets of dry arctic air.

A crisp northwester can hang of for days, and when it's done it leaves behing acres of bare mudflats along the rivers of the Chesapeake Bay. It literally blows the Bay out into the ocean.

Such a northwester hit last week, a day before we had our annual Severn River pickerel trip planned. John Page Williams, an old Bay hand, pondered the next move.

"We could wait it out," he said, listening to 25-knot winds whistle through the eaves of his frame house high above the river. "But frankly, I'd rather fish after one cold night than two or three. And maybe the low water will concentrate the fish in one spot. That's what the bass fishermen claim."

It may have been Williams' best guess of '78. It was no picnic on the Severn, with the wind blowing thr river into white foam all day and the cold snapping at our faces. But we caught pickerel like none of us ever had before in our lives.

By day's end we'd put three monsters in the live well and tossed a dozen and a half keepers back.

"I've heard of days like this," said our third man, charter boat skipper Dick Houghland, "but I never though I'd see one."

A pickerel, for the uninitiated, is a raunchy looking member of the pike family. Marylanders call a pickerel a pike though it actually is greenish, unlike the larger, silvery pike.

Pickerl and pike have the most awesome mouths of any freshwater fish. The head is huge and the mouth runs the length of it, stretching around a prehistoric snout.

Inside that mouth are rows of long, sharp teeth, which the stealthy pickerel use to capture and chew up minnows.

Pickerel are considered cold-water fish. They are thought to be easier to catch in winter because their food supply (minnows). is less plentiful and because shallow-water grasses pickerel hide in have largely died off.

They may be easier to catch but they are never easy. Even the best pickerel fisherman would consider a half-dozen decent fish an excellent day.

We were dreaming of that when we put the boat in at Williams' cove a half-mile upstream from the Route 50 bridge. We slid into hip waders and loaded up the bait (bull minnows) and the lures (small lead-head jigs).

We tried to home cove first, casting the jigs and minnows as well stalked along the shore in the 38-degree water.

We hadn't fished 15 minutes before Williams had a pickerel on, and when it started stripping four-pound-test line off the reel Houghland and I hurried over to see how big.

Nice fish," our host grunted, his rod bent double. The pickerel swirled 15 feet out, then headed straight for me. I leaped clear, kicking up cold spray as the fish screeched by.

Soon the pickerel was on the beach. Houghland guessed its length at about 25 inches and its weight at close to three pounds. A champion.

Tere were no more in that cove so we headed the boat downstream a quarter-mile toward the bridge. "I've heard this is a pickerel hole," Williams said, pointing right. "Let's give it a try,"

It was. The finest pickerel hole, in fact, that any of us had ever imagined. Pickerel are loners, but they appeared to be stacked up like cordwood in the six-foot depths just off shore.

Houghland and I each pulled out one to match Williams'. Then we all started hauling out smaller fish one after another. For awhile it was a bite on every other cast -- a pickerel blitz.

Eventually the fishing cooled. The pickerel got smart. Hwn they took the bait they played with it, so when we tried to set the hook we yanked the minnows out. The miracle was over. It had been something.

Winter pickerel fishing is doubly enjoyable because summer-playground rivers like the Magothy, Severn and South are full of fish but empty, at last, of fair-weather throngs of people.

When things slowed we went exploring. We found flocks of migrating swans tearing grasses from the mudflats. We hauled the boat through little guts against a raging incoming tide. We spooked giant herons from their roosts, quacked back at frantic flights of ducks, froze our noses and generally enjoyed our isolation.

We even picked up a few more fish.

There is one caution. Thirty-eitht degree water is a killer. We had a sturdy, seaworthy Mako boat and a mortor we could count on. But these are not rivers to play with in tippy craft. One must play it doubly safe, keeping in mind that if the boat goes down there'll be no help a-coming.