Hurricane Sandy Discussion 4

As a preface, the meteorological community reminds you not to get hung up on the category of this storm as it approaches land.  It is already well into its transitional phase to an extratropical storm. This only means the energy source for this storm is changing.

Extratropical storms have no category criteria.  Although you may stop hearing the word hurricane or tropical storm, this has absolutely no bearing on the real-world effects of this storm.

As Sunday afternoon continues, rain is falling across most Virginia’s peninsula communities and Metropolitan Hampton Roads. Winds in Norfolk are already gusting to 40 mph.

HPC rainfall forecast ending 8am ET, Wednesday, October 31. The area inside crimson red-shaded area should expect more than 2.5″ of rain from Sandy.

The overall forecast philosophy has changed little for our part our part of Virginia (Lynchburg, Danville, Roanoke, New River Valley, Lexington… and those surrounding counties).

The worst of this storm stays to the north.  The term epic gets tossed around a bit too easily nowadays.  But from Northern Virginia to coastal New England, it will be epic. Coastal areas will be flooded by ocean overwash.  Freshwater flooding of streams and creeks will be common.  Winds will be consistently 25-50 mph, with gusts to 70 mph, over a period of 12+ hours.  Power outages will be commonplace in these areas.  Transportation infrastructure will be severely damaged.  Sunday night through Tuesday is the time frame of greatest impact.

Current wind field around Sandy. The orange area includes winds 39+ mph. Red area is greater than 74 mph.

The wind field is huge around this storm, which is why there is so much concern about coastal issues in the Northeast.  Speed of winds and the size of the wind field are both key factors in the scope of coastal flooding and tree damage/power outages.

Locally, Monday will be cloudy, breezy, and chilly with occasional light to moderate rain. Focus of the rain will be in our northern counties, generally north of a line between Roanoke and Appomattox. Temperatures will be largely in the 40s to lower 50s.

Wind:

In our part of Virginia, the center of circulation goes by to our north, coming on shore in New Jersey, and continuing westward along the Mason-Dixon line.  This track gives us our peak winds Monday night and Tuesday.  Sustained winds of 25-40 mph will be common during that time, with some gusts to 60 mph during the daylight hours of Tuesday.  Areas along the Blue Ridge Parkway and westward may see gusts to 70 mph.  This is the time window when the damage threat also peaks… mainly downed trees and power lines.

Even once that level of wind begins to back off Tuesday night, there will still be some frequent winds of 20-30 mph through Wednesday, so additional power outages are possible.

Rain:

Most maddening about this forecast locally is the amount of rain.  There will be a strong cutoff to the heavy rain in Virginia… from northeast to southwest.  Ironically, it is plausible that Henry County, and an area in a 20-mile radius, gets less than a tenth of an inch of rain. While at the same time, 2 inches of rain are possible farther north toward Rockbridge and Nelson Counties.

All the data has been consistent in this rain shadow pattern, so we are not as concerned about flooding locally.  Best guess is that our viewing area does about 0.50-1.50″ of rain before the steadier rain comes to an end late Tuesday afternoon.

But it would not surprise me if many of our counties south and west of Lynchburg did less than that.  Would not surprise me at all.

County map of Virginia, for reference purposes.

Snow:

The theme here is unchanged as well.  Snow is a problem in West Virginia.  It is a foregone conclusion that the higher terrain in central and eastern West Virginia is going to get buried beneath 12-24″ of snow.  Snow there will start Monday night and probably continue through Wednesday.  Ski resorts will do close to 3 feet.

The wind direction makes it difficult to get that snow farther east.  Plus, the depth of the cold air through the atmosphere is not expected to be sufficient to support snow in our part of the state… at least for any substantial length of time.

New River Valley Counties, and those other counties that share a border with West Virginia, should not be surprised to see snow showers and squalls as the colder air works in early Tuesday morning… perhaps even as late as Wednesday.  But even in those counties, accumulations are not likely (exceptions in the very high terrain of those counties, see National Weather Service graphic below).

Roanoke Valley, Lynchburg, Danville all have a small opportunity to see a passing snow shower or two as the colder air moves in late Tuesday or Tuesday evening; the atmosphere will be horribly turbulent.  Could a coating happen Tuesday evening or Tuesday night?  Possible.  But not likely.

Temperatures:

The colder air wraps into our part of the state during Monday, so temperatures will spend much of the day in the 40s or lower 50s.  Tuesday through Friday will bring similar temperatures.  Highs generally in the 50s. Lows in the 30s.  Mountainous counties probably do no better than the 40s as late as Thursday.

National Weather Service Statements:

Current Statments from the National Weather Service Office in Blacksburg.

Yellow shaded areas under a High Wind Warning.  Green shaded areas (Alleghany and Bath Counties) also under the High Wind Warning… plus a Winter Storm Watch for elevations above 2500′.   Pink areas have the Winter Storm Watch, but not the High Wind Warning.

Sunday is the time to finish up preparations.  The start of Monday will not be dangerous, but conditions will gradually deteriorate late Monday afternoon and into Monday night.

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About seansublette

Meteorologist at Climate Central. Broadcast meteorologist in Virginia from 1995 to 2015. Born and raised in Richmond, VA. Penn State alumnus. Loves baseball and the rock band Rush. Views are independent of my employer. Past performance does not guarantee future results.
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