Kevin Myatt is The Roanoke Times' weather columnist.

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• We got graupel, but not on official record
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The Bermuda Triangle is interfering with winter.

A persistent ridge of high pressure off the Southeast U.S. coast, frequently centered near Bermuda, has prevailed throughout much of the past couple of months.

This big mound of stable, warm air has not been strong enough or large enough to completely cover us with warmth, so we've had quite a bit of seasonably cold weather. But it has been just strong enough to keep deflecting weather systems that could be winter storms for us into the Great Lakes and Ohio Valley instead.

Such a southeast ridge is a fairly common feature of a La Nina winter. La Nina is the recurring pattern of colder than normal waters in a streak through the central Pacific Ocean. La Nina is loosely correlated to overall mild and dry winter weather through much of the southern half of the United States.

The result of the Bermuda high is that the stronger low-pressure systems, rather than taking a track along the Gulf and then up the East Coast that could produce substantial snow or ice for our region, are instead cutting northeastward well to our west.

When they do this, the low-pressure systems' counterclockwise rotations draw up mild and moist air from the Gulf of Mexico to replace the cold air that has managed to build in between storms.

If the cold air is parked deep enough, shoved down the eastern slope of the Appalachians by high pressure in southeast Canada, there can be potential for a wintry mix, at least at the outset of precipitation. But more often, the warmer, moist air simply pushes out the cold air, and we get rain.

That's what happened this past weekend, and what is likely to happen toward the end of this week and into the last weekend of 2007.

If things set up just right, with lots of moisture being pulled northward along a stationary front marking the boundary between cold to the north and west and warm to the south and east, the rain later this week could be several inches.

Such a rainy period would be a welcome blessing to ease our long-term drought, and might give us a chance to avoid this being only the third year on record with less than 30 inches of rain in Roanoke. Roanoke had 28.8 inches of rain for the year through Tuesday.

Of more long-term interest will be whether the upcoming storm system will be strong enough to overcome the high-pressure system so much that it either weakens it or pushes it very far to the east.

Weakening or dislodging the Bermuda high could set the stage for much colder weather to fill the region come the first couple of weeks of January, and also offer the possibility that the storm tracks will be shoved farther south and east. But if it holds firm, we may continue to see storm systems cut northwest of us.

So we'll just have to see if this weekend's rainy storm wins its battle against the Bermuda Triangle. The result could well determine if winter reappears or disappears to start 2008.

On the edge for snow, again?

This morning, a low-pressure system spinning along the East Coast might be able to throw back enough moisture for some precipitation, especially east of Interstate 81. It will probably be just a few showers of something, with heavier precipitation staying east of us.

Temperatures will be borderline, once again. So while primarily rain is expected, don't be surprised to see a few pellets of sleet or flakes of snow.

Wherever the back edge of the heavier swath of precipitation occurs, there may be a period of moderate to briefly heavy snow. That will probably be well east of Roanoke, and is a very iffy proposition in any event.

We shouldn't be too surprised by yet another razor's-edge precipitation event. If this happens, it would make six for the month.