Winter 2004-2005: A Look Back

Overall our winter was warm with monthly average temperature across Southeast West Virginia, Southwest Virginia and Northwest North Carolina of 2-5 degrees (F) above normal. The first half of each month was warm, especially January, where temperatures were 15-20 degrees (F) above normal. Record high temperatures in early January had people wondering, is winter over already? The second half of December and January reminded us that winter was still around as Arctic blasts of cold air dropped temperatures below zero across portions of the mountains and into the teens and single digits along and east of the Blue Ridge. It seemed the closer we got to Spring (March 20), the colder the temperatures remained.

 

Snow was also hard to come by for most of the winter. Snowfall totals remained below normal through February 26 except in Southeast West Virginia, where a few long duration (36-48 hours) upslope snow showers kept totals at or above normal. Three disorganized systems showed the potential to bring significant amounts of snow to at least the mountains in January and early February. However, warm air intruded aloft and kept precipitation as a mix of mostly sleet. Late February, a well-organized system tracked from the Gulf of Mexico to along the Mid Atlantic coast. This system did not disappoint snow lovers, bringing significant amounts of snow to the area. From that day on and at least in the mountains, it seemed as if the snow would not stop. Several clippers from Canada continued to reinforce the cold air and brought snow to the region every one to two days. Accumulations from these clippers were relatively small (1-3 inches) and did not last too long thanks to the increasing sun angle of March.

 

As the Data tables and graphs (click to enlarge) shows below, this was an abnormal winter considering monthly temperatures were above normal and snowfall amounts were below normal for much of the winter season. However, climatology does show these abnormal conditions from time to time. This years winter conditions typically occur during a weak El Nino phase. A weak El Nino is positive sea surface temperature (SST) in the equatorial Pacific of a half of a degree (+0.5C). A strong El Nino is a positive sea surface temperature of 1(C). For more information on El Nino, visit the Climate Prediction Center (CPC) web site at: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml. It was also interesting to note that the contiguous United States was 2.8 degrees (F) above normal. No state was cooler than average during the winter.You can read more about the contiguous United States 2004-2005 winter weather at http://www.noaanews.noaa.gov/stories2005/s2405.htm.

Temperature - Precipitation Graph

 

Temperature - Precipitation Graph

 

Temperature - Precipitation Graph

 

Temperature - Precipitation Graph

 

Temperature - Precipitation Graph

Cooperative Weather Station Map

Monthly break down:

November 2004 (Data Tables)

An active sub-tropical jet (Southern branch jet stream) kept temperatures mild and above normal (+2 to +5F) for November. The areas first frost/freeze did not occur until late in the month across the mountains and not until early December in the east. The average first frost for the mountains typically occurs in early October and in the east late October.

 

Several waves tracking out of the southwestern United States during the month brought above normal (1-2 inches) monthly rainfall to the area. Despite a few flurries being reported in Southeast West Virginia, warm temperatures kept precipitation as rain. The data tables displays the maximum daily temperatures and precipitation (rain and snow), observed and normal monthly temperatures and precipitation and departures for first order stations (Roanoke, Lynchburg, Danville, Blacksburg, and Bluefield) across NWS Blacksburg county warning area.

December 2004 (Data Tables)

A less active sub-tropical jet still brought unseasonably warm (15-20 F above normal) temperatures to the area the first part of the month. This warmth was off set by an Arctic plunge of cold air which dropped temperatures 20-30 degrees (F) below normal a week before Christmas. The extreme above and below normal temperatures canceled each other out allowing December's monthly temperature to average near normal.

 

Most of the area was snow starved (1 to 4 inches below normal) for the month except Southeast West Virginia (2.5 inches) where northwest flow and low level moisture brought above normal monthly snowfall. There was no White Christmas this year. Instead, Old ManWinter brought significant snow to areas not noted for snow on December 25-26, the Texas Gulf coast and southeastern United States. Dry high pressure over the northeastern United States kept snow farther south than normal as a low pressure system tracked through the Carolinas. With the exception of southeast West Virginia (0.65 inches), rainfall totals were also below normal (0.75 to 1.00 inch).

Visible Satellite Image of snow cover

Visible Satellite Image showing the swath of snow/sleet cover at midday on December 27, 2004. Courtesy of NWS RAH.

 

January 2005 (Data Tables)

A "Bipolar" month with high and low temperatures running well above and below normal. Under a strong ridge of high pressure, the first half of the month saw a few records broken as temperatures soared into the mid to upper 60s across the west and lower to mid 70s in the east. Overnight lows also remained above normal the first couple of weeks of January. Spring-like weather in the form of severe thunderstorms and flooding was also reported, leading some people to wonder, was winter over? Very unseasonably high dew points (lower to mid 60s) moved into the area on January 14th. This moisture combined with a slow moving cold front to produce a large swath of rain across the region. Upslope southeast winds into the Blue Ridge in northwest North Carolina and southwest Virginia ahead of the cold front produced an area of persistent heavy rain. Rain rates were around an inch an hour, and total rainfall amounts in a 3 to 4 hour period ranged from 2.5 to 3.5 inches. In northwest North Carolina, flooding was reported in Watauga and Surry counties. Flooding was particularly bad along the Ararat River in Surry county, with flood damage to approximately 50 homes and 10 businesses. In southwest Virginia, flooding was reported in Patrick, Franklin and Amherst counties. Minor flooding occurred along the Dan River at South Boston, the Roanoke River at Randolph, and the James River at Bremo Bluff. The unstable atmosphere also produced rotating thunderstorms and led to the issuance of a couple of Tornado Watches and four Tornado Warnings for the area. No tornadoes were confirmed, however one severe thunderstorm brought damaging winds to the west side of Danville, partially blowing a roof off an apartment complex. After the bout of severe weather, an Arctic blast of cold air in the second half of the month brought back the reality of winter and wind chills as low as -15F. Despite the temperatures dropping well below normal, early January record warmth kept monthly mean temperatures 4-5 degrees (F) above normal.

 

Cold air in place the latter half of the month, combined with a few storms tracking close by, brought a wintry mix of snow, sleet and freezing rain to the region. On January 20-21 (upslope 22-23), a low pressure system tracked to the northeast coast becoming a major Nor'easter. This brought significant snowfall to the New England states. As this system tracked close to our area, warm air was allowed to intrude aloft, bringing a wintry mix of mostly sleet and some snow to Northwest North Carolina and the Southwest Virginia mountains. The Greenbrier Valley and Virginia Highlands stayed in the cold air and saw mostly snow. The foothills and piedmont sections of southern Virginia and northern North Carolina saw a wintry mix of snow, sleet and freezing rain. It was this warm air aloft that allowed more sleet to fall limiting the amount of snow to 1-3 inches. On January 29th (29th ice) another disorganized storm tracked from Southern California and into Northern Virginia. As this system moved through the Tennessee Valley, a coastal low formed off the Carolinas. This system tracked differently, but produced the same results; a wintry mix of snow, sleet, and freezing rain, keeping snow amounts low.

 

Snowfall Map
Snowfall Map
Snowfall totals Jan. 20-21 (Click to enlarge)
Snowfall total Jan. 22-23, 2005 (Click to enlarge)
Snowfall Map
Ice Event Map
Snowfall totals Jan. 29-30, 2005 (Click to enlarge)
Ice Accretion totals Jan. 29-30, 2005 (Click to enlarge)

 

February 2005 (Data Tables)

 

We experienced another seesaw month for temperatures, but not as extreme as January. A cold start to the month was replaced by temperatures 15-20 degrees (F) above normal by the end of the first week. Was this the end of winter? Unfortunately not, as Punxsutawney Phil saw his shadow and forecasted six more weeks of winter. Temperatures every three days or so bounced around from cold to warm back to cold, typically noted in March and early April. Despite the bouncing around of daily temperatures, monthly temperatures were 2 to 4 degrees above normal.

A third disorganized winter system (Feb 3rd snow and ice) plagued the region bringing another round of wintry mix to the area. Just like January, warm air produced mostly sleet and kept snow amounts low. As the Spring Equinox approached and days were getting longer, the hopes of a good winter snow for the Mid Atlantic region were declining. The western slopes across southeast West Virginia were hoping for the snow to stop. On February 10th, a long duration upslope snow event (36-48 hours) produced snow totals from a trace to 5 inches on western slopes of southeast West Virginia. Greenbrier County saw 1 to 8 inches. Late in the month, a low pressure system tracked into the Gulf of Mexico and the along the Mid Atlantic coast. Finally, the snow everyone was waiting for was here. This one storm (February 28th) brought monthly snowfall totals to 3 to 5 inches above normal .

 

Snowfall Map
Ice Event Map
Snowfall totals Feb. 3, 2005 (Click to enlarge)
Ice Accretion totals Feb. 3, 2005 (Click to enlarge)
Snowfall Map
Snowfall Map
Snowfall totals Feb. 10-11, 2005 (Click to enlarge)
Snowfall totals Feb. 27-28, 2005 (Click to enlarge)

 

 

 

March 2004 (Data Tables)

Punxsutawney Phil was right because as March rolled in, cold air remained. On the heels of the February 27-28 storm, northwest flow continued to bring additional snowfall to the western slopes of Southeast West Virginia and northwest North Carolina (Mar 1-2). This prolonged event produced significant bands of snow as well as blowing and drifting snow. Some of these drifts were several feet high, covering roads and making them impassable. A couple of clippers from Canada (Mar 11-12 and Mar 16-17) kept the snow falling across the area which seemed like days. Each of these clippers brought an average of 1-3 inches of snow to the area. These two mid month clippers were good snows as accumulations remained mostly on grassy surfaces and melted quickly under the March sun.

 

Monthly temperatures were 2-4 degrees (F) below normal as the area remained under an upper level trough. Most of the snow and rain fell across the mountains bringing slightly above normal monthly precipitation. Southeast West Virginia saw the brunt of the snow and rain and registered 15.6 inches above normal snowfall. Eastern sections of the county warning area saw mostly cloud conditions as precipitation amounts were below normal.

 

Snowfall Map

 

Snowfalls totals Mar. 1-2, 2005 (Click to enlarge)

 

 

 

 

 

Spring-Summer 2005: a Look Ahead:

SPRING OUTLOOK:

Spring Outlook Map
Spring Outlook Map
(Click to enlarge)
(Click to enlarge)

For a more details on this year's spring outlook, visit http://www.noaanews.noaa.gov/stories2005/s2406.htm

 

SUMMER OUTLOOK:

 

Summer Outlook Map
Summer Outlook Map
(Click to enlarge)
(Click to enlarge)

For more forecast outlooks, visit the Climate Prediction Center's web site at http://www.cpc.ncep.noaa.gov/products/forecasts/

 

Late Spring/Summer Flood Outlook:

There are several factors to consider when assessing the potential for river flooding in the area during the warm season (May through August). Widespread heavy rainfall is the most important factor to cause river flooding, but others include the wetness of the soils, streamflows, and reservoir levels. Despite the fact that precipitation across the area over the winter was a little below normal, streamflows and reservoir levels were all near normal. Soil moisture was also near normal in the foothills and piedmont, while the mountains remained unusually moist. Taking all of these factors into consideration, there are no strong signals for either a greater than normal or less than normal threat of river flooding for the area.

As is usually the case, the prospect for widespread heavy rainfall is the deciding factor for the chance of flooding this warm season. The long range forecast for the season indicates that we have equal chances of being above or below normal on rainfall. That would indicate that the outlook for widespread heavy rain and river flooding this warm season is near normal.

However, there is another tool that can be used to assess the potential for river flooding, and it's called AHPS, or Advanced Hydrologic Prediction Service. This is a National Weather Service application on the web that shows probabilistic forecasts of river levels. These forecasts are based on current streamflow and basin conditions, along with historic precipitation data. AHPS can be accesses on the web at:

http://ahps.erh.noaa.gov/cgi-bin/ahps.cgi?rnk

AHPS also indicates that most rivers in the area would have a near normal chance of flooding through June. The exception would be at South Boston on the Dan River, where there is a 5 to 25 percent higher chance of flooding than what has been historically observed. The rest of the Dan River and the Roanoke River also have a 5 to 25 percent higher chance of flooding through the end of April. The James River has a 5 to 10 percent higher chance of flooding through the end of April.

Another way that meteorologists use climatology for forecasting heavy rainfall is to look for weather patterns that have brought widespread heavy rainfall to the area in the past. A study of heavy rainfall events during a 31 year period, (1964 -1994), showed that there are basically 3 weather patterns which bring widespread heavy rainfall to the area during the warm season. One of those patterns is quite familiar to people in the area, especially after last year. One of the primary weather patterns that brings heavy rain to northwest North Carolina, southwest Virginia and southeast West Virginia during the warm season (and often into October) is when remnants of tropical storms track inland near the area. This scenario has typically produced some of the area's most devastating floods. You can read about tropical weather that affects the region in our Tropical Weather Section.

However, there have been major floods with a couple of other weather patterns, which meteorologists can look for. These other two patterns are:

Stalled Fronts- this is a weather pattern where a cold front moving into the western slopes of the Appalachians slows down and becomes nearly stationary. Generally, 1 or more low pressures ride northeast along the front and provide the focus for widespread shower and thunderstorm development in the warm moist air streaming northeastward into the area. Below is a composite surface chart of the 10 cases observed in the study, and also the location of deep moisture and low-level flow. There was no preferred month for this pattern in the warm season, with 2 cases in May, 3 in June, 3 in July and 2 in August. This particular pattern has brought very heavy rainfall events to the Appalachian Mountains in the past, particularly far southwest Virginia and southeast West Virginia.

 

Weather Map
Weather Map
(Click to enlarge)
(Click to enlarge)

 

 

Upslope Flow- this is a weather pattern where there is a prolonged period of a southeast flow of unstable air into the Blue Ridge foothills and mountains. This southeast flow is perpendicular to the mountains, and the moist air rises as it moves into higher terrain. This provides additional lift for shower and thunderstorm development, while also focusing the heaviest rainfall right along the Blue Ridge. Below is a composite surface chart of the 10 cases observed in the study, and also the location of deep moisture and low level flow. The upslope heavy rain pattern occurred most often in May, with 6 cases, but there were also 3 cases in July and 2 in August. This particular pattern has brought very heavy rainfall events to the Blue Ridge mountains and foothills in the past, from the northern mountains and foothills of northwest North Carolina, northeast into southwest Virginia. The heavy rain then causes river flooding downstream in the piedmonts of northwest North Carolina and southwest Virginia.

Weather Map
Weather Map
(Click to enlarge)
(Click to enlarge)

Frost-Freeze Program:

The Southern Appalachian's trees and plants are beginning to bloom. Based on climatology, there is still the possibility that cold air could filter into the region bringing a late season frost or freeze. Those with agriculture interest will need to monitor the weather and protect their interest if a frost does happen. The map below displays the average last frost for the area. If a frost or freeze is expected in the area after these dates, a frost advisory or freeze watch/warning will be issued by the National Weather Service.

 

Frost Zone Map
(Click to enlarge)

 

 

Have you ever wondered what was the hottest or coldest summer? When it seems like the rain will never end, do you ponder if this is the wettest spring on record? Hopefully all your Spring and Summer weather questions will be answered in our Top 10 SPRING-SUMMER List. This list was compiled from data received from the National Climatic Data Center (NCDC) in Asheville NC. If you have more weather questions not covered in this article, visit NCDC or SERCC (Southeast Regional Climate Center) web site.

The NWS Blacksburg staff would like to thank our loyal and faithful trained weather spotters, Department of Transportation (WVDOT, VDOT, and NCDOT), County Emergency Managers and county 911 centers for their winter weather reports. Snowfall and Ice Accretion maps in this article were generated from these reports.

This climate article was written by:

Robert Stonefield

Jan Jackson