Charles City, Virginia

... Record November maximum rainfall set at Norfolk VA...

A record monthly maximum rainfall of 9.20 inches was set at Norfolk
VA in November 2009. This breaks the old record of 7.01 set in 1951.

     ****************************************************
    winter preparedness week in Virginia and North Carolina
                 November 29-December 5, 2009
     ****************************************************

The governors of Virginia and North Carolina have declared the week
of November 29 to December 5, 2009 is winter preparedness week. The
National Weather Service /NWS/ offices serving Virginia and North
Carolina... in cooperation with their respective departments of
emergency management... will send public information statements over
the NOAA weather wire service each day through Saturday at
approximately 11 am and 3 PM EST. These statements will focus on
different aspects of winter weather in the mid Atlantic region... and
preparedness actions the public should take for the upcoming winter
season.

Today's topic - snow... sleet and freezing rain... how do they form?

Several winter weather situations affected Virginia last winter...
bringing snow and/or mixed precipitation to the commonwealth. And... as
many of US remember, the 1998-99 winter had 2 memorable ice events.
For many in central... southern and eastern Virginia... the Christmas
eve ice storm will long be remembered. Trees... laden with one-half inch
to an inch and a half of ice snapped like toothpicks... knocking down
trees and power lines... and shutting off power out power to several
hundred thousand customers. Some were without power for as long as 10
days. Many spent Christmas with no heat and no lights... giving a taste
of what it must have been like for early American settlers.

In addition to the power outages... many primary and secondary roads were
littered with downed trees and tree limbs. Portions of Interstate 64
were temporarily closed due to tree debris. Fortunately... the Christmas
eve ice storm was not accompanied by bitterly cold temperatures... which
obviously would have made the situation much worse.

An ice storm of similar magnitude struck northern Virginia on January
14-15 1999. One-quarter to one inch of ice accumulation caused many
accidents... downed many trees... and knocked out power to more than two
hundred thousand customers. Accidents temporarily closed portions of
several primary roads... including the Dulles toll Road... snarling
traffic for hours. Downed trees also caused part of Interstate 95 to
be temporarily shut down.

Many virginians will also remember the multiple ice storms during the
1993-94 winter. Unlike the storms of 1998-99... several of these storms
were accompanied by very cold temperatures... which inhibited the
melting of the ice and prolonged recovery efforts.

Forecasting whether a particular winter storm will produce snow, ice,
rain, or a mixture of precipitation is one of the most difficult
forecast problems meteorologists face. Virginia's close proximity to
both the Atlantic Ocean and a cold air source over eastern Canada and
New England make forecasting the exact position of the rain/snow line
a major forecast challenge. In fact, a deviation in forecast storm
track of only 50 miles can mean the difference between a foot of snow,
an inch of ice, or two inches of rain.

The key factor in determining precipitation type with a particular
winter storm is the depth of cold air above the ground. If the air
from ground level up several thousand feet is above freezing, rain
will fall. If the air from the ground up through the depth of the
atmosphere is below freezing, snow will fall. However, if cold
air is entrenched at the ground with a layer of warm air above it,
sleet and/or freezing rain are likely.

     For sleet to fall... the cold air near the ground must be deep
     enough to allow the raindrops falling through to re-freeze
     before reaching the ground.

     For freezing rain to fall... cold air near the ground is shallow.
     Raindrops remain in liquid form until they contact objects at
     ground level.

All three of these precipitation types can cause significant
disruption to our normal daily activities. Slick or icy roads
provide a Haven for motor vehicle accidents, and potentially
massive traffic jams. At the very least driving speeds will be
slowed significantly by snowy or icy conditions. Walking on an ice
covered street or sidewalk can be adventurous or even prohibitive.

By keeping abreast of the latest forecasts through NOAA Weather
Radio or your local TV and radio stations, you will be better
prepared to handle winter's weather elements, whatever they may
be!

Below is a link to the NOAA winter outlook for 2009-10.

Http://www.Noaanews.NOAA.Gov/stories2009/20091015_winteroutlook.Html

Additional information on winter weather preparedness can be
obtained on-line through the Virginia department of emergency
management home Page. The url is (in lower case):

    http://www.Vaemergency.Com/threats/winter/index.Cfm

In addition... the ready Virginia and ready North Carolina web
sites haves been developed to aid virginians and north carolinians
in their overall disaster preparedness. The urls are:

    http://www.Readyvirginia.Gov/ /English version/
    http://www.Listovirginia.Gov/ /Spanish version/
    http://readync.Org/ /English version/
    http://listonc.Org/ /Spanish version/

Up-to-date weather information is also available on-line from the
following National Weather Service sites (all urls in lower case):

NWS Wakefield - http://weather.Gov/akq
NWS Sterling - http://weather.Gov/lwx
NWS Blacksburg - http://weather.Gov/rnk
NWS Charleston WV - http://weather.Gov/rlx
NWS Morristown TN - http://www.Srh.NOAA.Gov/mrx
NWS Raleigh NC - http://weather.Gov/rah

National Weather Service winter weather awareness home Page -

Http://www.NWS.NOAA.Gov/om/winter/index.Shtml

Bill sammler
warning coordination meteorologist
NOAA/National Weather Service
Wakefield VA