January 29-30, 2010 Winter Storm|
...This winter storm produced a large
swath of snow and ice that extended across the southern Rockies into the Southern Plains, Tennessee Valley and eventually the Carolinas and
...Winter Storm Watches were issued for all 31 counties and verified with no false alarms or
missed events. The average lead time for all of the watches was 52 hours. Winter Storm Warnings
were issued for all 31 counties as well with no false alarms or missed events. The average lead time
for all of the Winter Storm Warnings was 33 hours...
...The Raleigh News and Observer reported that there were 1,000 car accidents across the
state, some power outages especially in the Southern Piedmont and Mountains, several injuries from
car and sledding accidents and one fatality when a pedestrian was killed by snowplow in Wayne County...
...The event followed a hybrid "Miller A/B" surface pattern in which a primary storm system
tracks northeastward across the Southeast toward the southern Appalachians with other weak areas of
low pressure or troughs extending north and northeast
from the low center. This pattern results in a somewhat complex vertical thermal
pattern with broad areas of mixed precipitation...
...Nearly 1-2 inches of sleet were observed in central North Carolina which led to reduced snow
accumulations but increased longevity of the snow cover...
The surface pattern during the event was consistent with many past significant winter
storms in central North Carolina with a storm system tracking east and then northeast
across the northern Gulf Coast along with an arctic air mass centered across the eastern Great Lakes.
A strong cold front crossed central North Carolina
around 00 UTC on 1/29 and then pushed south
into southern Alabama and southern Georgia by 12 UTC on 1/29. A strong 1036 MB arctic
high pressure system moved into the Great
Lakes region by 18 UTC on 1/29 with subzero dew points.
The presence of this very strong, very cold air mass to our north was key in setting
the stage for a potential winter storm. As a low
pressure system moved east from the Texas
coast at 12 UTC to the Louisiana-Mississippi
state line by 00 UTC on 1/30, an overrunning
pattern developed across the Southeast, with the advection of
warm air aloft riding up and over
cold air near the surface. The arctic high
pressure system to our north was strong enough
and in a favorable location across the eastern Great Lakes during the evening of 1/29, to
provide a steady supply of cold low level air into central North Carolina.
Higher up in the atmosphere, moisture and lift, two important ingredients for
precipitation, steadily increased over North Carolina. At 850 mb, a warm front over
the Gulf Coast states began moving northeastward, accompanied by strong confluent southerly
flow. By 00 UTC on 1/30, a 40
knot low level jet stretching from the Gulf of Mexico up toward
the southern Appalachians was pumping considerable moisture up into the Carolinas, up and
over the low level cold air which was locked in over central North Carolina. A
at 500 mb, located over New Mexico at 00 UTC on 1/29, moved east across the
lower Mississippi valley through the 30th, weakening to an
open wave as it moved into the
southern Appalachians by 00 UTC on 1/31. The approach of this wave brought
increased moisture as well as strong lift over North Carolina, supporting the outbreak of
precipitation. In the upper levels at 300 mb, upward motion over North Carolina was further
intensified by upper level divergence in the right entrance region of the 175 knot jet
over New England at 00 UTC on 1/30. All of these factors combined to
lead to the development of deep, prolonged, moist upward motion over the region.
Precipitation quickly spread across central North Carolina during the
late afternoon and
evening of 1/29. By
midnight, much of the
precipitation had shifted north and east of central North Carolina as
a large area of convection developed across southern Georgia and Alabama.
Precipitation returned to
central North Carolina a few hours after midnight and
continued into the morning of 1/30 as
the surface low moved northeast, reaching
southern Georgia by 12 UTC on 1/30. The surface
high pressure system had weakened slightly but remained in a very favorable location to
pump low level cold air into central North Carolina, while farther aloft, warmer air kept
trying to push over the low level cold air. As a result, precipitation types continued as
a wintry mix through 1/30. Over the northern half of central North Carolina, where the low
level cold air was deepest and the warm air advection aloft was weak, precipitation fell
as mostly snow and sleet. In southern sections, where the surface-based cold layer was
shallow with stronger warm air advection aloft, the precipitation was mainly a mixture of
sleet and freezing rain.
By 18 UTC on 1/30, the storm system had reorganized off the Southeast coastline and was
beginning to depart the region. With the nose of the low level jet heading to our east,
the mid level trough axis weakening further and shearing out over
the Southeast, and the
upper level jet core over New England heading out over the Atlantic,
the lift over North Carolina was diminishing quickly, and precipitation ended from west to east during
the early afternoon on 1/30.
A large swath of 6-10 inches of snow with a little sleet fell across northern and western North Carolina with
some locations immediately near the Virginia border and in the higher elevations of the
mountains receiving around a foot of snow. Further south, 2-6 inches of snow and sleet fell along with some
freezing rain fell across a good portion of the Piedmont including the Triangle and Charlotte metro areas.
Around an inch of sleet with a little snow and up to a quarter of an inch of freezing rain fell across
portions of the Southern Piedmont, Sandhills, southern Coastal Plain and central coastal region.
Much of the precipitation on the 29th fell as snow in Greensboro (KGSO), Raleigh (KRDU), and
the NWS office in Raleigh (KRAH). On the 30th, sleet mixed in with the snow during the early morning hours. ,
Most of the precipitation in Raleigh fell as sleet after 400 AM while in Greensboro, the snow changed to mainly
sleet after 900 AM. The mixed precipitation resulted in low snow ratios as seen in the table below.
Snow/Sleet and Freezing Rain Accumulation Maps
MODIS Terra Satellite Image Showing Snow Cover from 2010/01/31