Snow Event December 5, 2005

SNOWFALL ACCUMULATION MAP

Snow Reports

 

NOUS41 KAKQ 060054
PNSAKQ
MDZ021>025-NCZ012>017-030>032-102-VAZ048-049-060>100-061247-

PUBLIC INFORMATION STATEMENT
SPOTTER REPORTS
NATIONAL WEATHER SERVICE WAKEFIELD VA
747 PM EST MON DEC 5 2005

THE FOLLOWING ARE UNOFFICIAL OBSERVATIONS TAKEN DURING THE PAST 24 HOURS FOR
THE STORM THAT HAS BEEN AFFECTING OUR REGION. APPRECIATION IS EXTENDED
TO HIGHWAY DEPARTMENTS...COOPERATIVE OBSERVERS...SKYWARN SPOTTERS AND MEDIA FOR
THESE REPORTS. THIS SUMMARY IS ALSO AVAILABLE ON OUR HOME PAGE AT
WEATHER.GOV/WAKEFIELD

***********************SNOW ON GROUND***********************

LOCATION SNOW TIME/DATE COMMENTS
ON GROUND OF
(INCHES) MEASUREMENT

MARYLAND

...WICOMICO COUNTY...
SALISBURY 1.0 737 PM 12/5

VIRGINIA

...ACCOMACK COUNTY...
WALLOPS ISLAND 1.5 735 PM 12/5

...ESSEX COUNTY 7.0 750 PM 12/5
TAPPAHANNOCK

...HENRICO COUNTY 3.0 738 PM 12/5
SANDSTON

...KING WILLIAM 1.8 735 PM 12/5
STUDLEY

December 5, 2005 Winter Storm
Preliminary - Updated


Event Headlines

...The December 5th Storm across portions of Virginia and Maryland was the 1st notable winter storm to affect the Wakefield, VA county warning area for the 2005-2006 season...
...The storm was characterized by significant differences in precipitation amounts and precipitation types over short distances...
...Portions of central and east central Virginia and the lower eastern shore of Maryland received significant accumulations of snow and sleet.


Event Overview

A relatively early season storm brought snow and sleet to portions of central and east-central Virginia and the lower eastern shore of Maryland, with all rain for southeast Virginia and northeast North Carolina throughout the day of the 5th, continuing into the early morning hours of the 6th. After a balmy day Sunday the 4th, when temperatures soared into the mid 60s at Richmond and Norfolk, and 57 F at Salisbury, Maryland, the event gradually developed during the late evening hours of December 4th, as developing low pressure over the deep south combined with colder air filtering down from the northwest. Widespread rain began after 1 am on the 5th as temperatures dropped into the lower 40s at Farmville and Richmond. The rain briefly mixed with sleet before changing to mainly snow with occasional sleet after 4 am for areas along and north of a Farmville to Richmond line. By afternoon, this line extended northeastward through the northern Neck to a position near Wallops Island, with areas along and to the north continuing with mainly snow, mixed at times with sleet, while areas to the south had moderate to heavy rain. The rain/snow line moved a bit farther northward during the evening, then back south as the precipitation ended as snow or rain showers early on the morning of the 6th.


Synoptic Overview

This snow, sleet, and rain event was associated with a pattern of warm advection through the low to mid layers of the atmosphere. This pattern is characterized by a relatively simple mean sea level pressure pattern where a fairly weak surface low tracks northeastward across Georgia and the Carolinas, with a surface high pressure center located to the north. Unlike the "Miller B" storms when cold air is already locked in place across the mid-Atlantic, this type of storm begins with relatively warm temperatures that drop as the storm initiates, and cold air continually filters in from the north or northwest. With this particular storm, the surface low developed in the Gulf of Mexico in response to an amplifying mid level trough moving into the southern Plains states. The low then tracked northeastward and was located near Athens, GA by early Monday afternoon, and was off the North Carolina and Virginia coast by early Tuesday morning.
Precipitation began as very spotty areas of light rain during the evening of Sunday the 4th, with most locations clouding up, but remaining dry. The precipitation shield then became more widespread after midnight, as a strong core of the upper jet stream (located about 35,000 feet above the ground) approached the region from the southwest. In addition, winds in the low levels up through about the 850 mb layer (roughly 5,000 feet above the ground) became convergent across southern Virginia, with southerly flow south of this line converging with northerly flow moving southward from Pennsylvania. The convergence in the low levels combined with divergence aloft with the right entrance region of the upper jet allowed sufficient uplift to develop. Above the 850 mb layer, winds were generally southwest out ahead of the approaching trough, allowing for ample moisture feed from the Gulf of Mexico.

By daybreak and throughout the day of December 5th, moderate to occasionally heavy precipitation continually tracked along the zone of low-level convergence from near Danville, VA east-northeastward into Accomack county on the Virginia eastern shore. Meanwhile the surface high to the north kept somewhat drier air in place across Louisa and Fluvanna counties, keeping the snow there relatively light. Radar imagery during the mid-morning hours depicts the heaviest line of precipitation, mainly sleet from just south of Farmville to near Chester and Hopewell, VA. Just north of this line, Richmond was reporting moderate snow, while just south it was all rain. This setup more or less continued through the afternoon hours. By late afternoon and early evening, much of the region from Amelia County eastward to Richmond and into the northern Neck had received 3 to 4 inches of snowfall. Radar and satellite imagery at 6 pm showed that the back edge of the precipitation had moved to near Farmville and Danville. However, the storm was not over, as the main surface low at this point was still located in South Carolina. By late Monday night into early Tuesday morning, the surface low strengthened offshore and a deformation zone in the mid levels formed across Virginia and Maryland, enabling wrap around moisture to bring additional snow accumulations to Louisa, Caroline, and Hanover counties in central Virginia, and portions of Maryland from Salisbury westward. At Ocean City enough low level warm air came in from the Atlantic to turn the snow over to rain, limiting accumulations along the immediate coast. Snow / Sleet Accumulation Map

The corridor of heaviest snow and sleet accumulation fell in a fairly narrow band from just north of Farmville up to Louisa eastward across the Richmond metro area into the northern Neck and up through inland portions of the Maryland eastern shore, generally from Salisbury west to Cambridge. Most locations in this band received 3 to 4 inches of snow and sleet, with locally up to 6 or 7 inches near Tappahannock and across northern Dorchester County in Maryland. As is often the case, there was a sharp cutoff of accumulation near the rain/snow line, which in this case set up across the southern suburbs of metro Richmond. The Richmond Airport recorded a total of 4.4" of snow (and sleet) for the event, while Petersburg, just over 20 miles to the south received about half an inch.