The Blizzard of '93
March 12-14, 1993: A historic snowfall across the Tennessee Valley and Southern Appalachians
Event Overview
Whether referred to as the "Storm of the Century", or simply "the blizzard" to those of the Southern Appalachians, this historic snowfall will not soon be forgotten.
On March 12-14, 1993, a powerful cyclone developed near southern Texas and tracked northeastward, bringing impacts from the Gulf Coast all the way to Maine. 15 tornadoes struck in Florida, killing 44 people with storm surge of over 12 feet also leading to at least seven deaths. However, when the storm collided with Arctic air already dominating the U.S., precipitation was changed to snow from the Deep South all the way into Canada. The impressive strength of the cyclone and extent of cold air produced a swath of strong winds, dangerous wind chills, and record-breaking snowfall in these areas. Within the modern County Warning Area (CWA) of the Morristown, TN forecast office, impacts were widespread and crippling with 10 to 20 inches of snow across the entire area with multiple feet of snow in the mountains. Snow drifts of several feet occurred in the Valley with portions of the mountains receiving drifts of over 10 feet. Thousands were stranded and/or without power for days. This presentation will examine meteorology, snowfall totals, and impacts from this event that occurred 30 years ago.
Synoptic Pattern
Thursday, March 11, 1993
Leading up to the event, the most notable synoptic feature was strong arctic high pressure dominating across the Great Plains and central U.S. A stationary frontal boundary is also noted across the southern tier of the U.S., separating the arctic high and warm, moist airmass over the Gulf. Aloft, the flow is quasi-zonal in the lower 48 with numerous smaller waves noted. A feature of interest off to the northwest is strong upper ridging, commonly seen in a positive Pacific/North American pattern (PNA) phase. This will work to enhance downstream troughing into Friday.
Friday, March 12, 1993
The Storm of the Century began its life cycle much like any other systems - a weak low pressure system developing near the Texas Coast. But the ingredients were coming together for the development of a record-setting storm.
The first ingredient to creating this monster system was warm water in the Gulf of Mexico. The waters of the Gulf were unusually warm for that time of year. Warm, moist air at the surface can create potentially unstable conditions, and this instability can be released if other ingredients come into place.
The next ingredient was a cold air mass building southward across the continental United States. The surface analysis on Friday, March 12 at 7 AM (image to the right) showed a strong high pressure system over the northern Rockies extending southeast into Texas. There were also two high pressure centers near the East Coast. These high pressure systems supplied cold air to the Gulf Coast region. While this wasn’t an extremely cold air mass, it did bring temperatures in the 40s down to the Gulf Coast. This was cold enough to create a large temperature difference from the coast to the warm Gulf waters and strengthen a stationary front across the Gulf. A sharp temperature difference across a front enhances the winds on either side of the front, leading to stronger convergence of winds - southerly winds running into northerly winds. This convergence of winds at the surface would aid in the low’s rapid intensification.
Winter Storm Warning issued by the Memphis, TN National Weather Service Office.
Other critical ingredients were coming together higher in the atmosphere. The analysis of 500 mb heights on March 12th at 7 AM (depicted on the right) shows two troughs, indicated by the red lines - one across the northern Plains and Rockies, and one in Texas and northern Mexico. In addition, there are two jets over the United States, indicated by the yellow circles - one aligned north-to-south across the Rockies, and one aligned west-to-east across the Ohio Valley and Mid-Atlantic regions. These troughs and jets would align to create ideal conditions for rapid intensification of the low pressure system as it tracked east across the Gulf of Mexico.
Saturday, March 13, 1993
The low pressure system began to rapidly intensify during the afternoon and evening of Friday, March 12th and the early morning hours of Saturday, March 13th. All the ingredients were coming together for a storm of historic proportions along the east coast.
The center of the surface low tracked northeast across the northern Gulf of Mexico, into the Florida Panhandle, and near Savannah, Georgia by 7 AM (image to the right). At this time, which was less than 24 hours after beginning its development over the western Gulf, the low had a minimum central pressure of about 970 millibars, comparable to many category two hurricanes.
In the upper levels of the atmosphere, the two troughs (indicated by red lines in the previous image) merged into one larger, negatively-tilted trough. An upper level trough with a negative tilt (like a backslash, “\”), tends to produce greater instability than a neutral or positively-tilted trough. Greater instability allows air to rise faster, which increases the strength of the surface low pressure center. At this point in its development, the storm took on a comma-shaped appearance on satellite imagery (shown previously) - a classic sign of an intense storm system.
The two jet streaks (from the 500mb map on Friday the 12th) moved into favorable positions to further intensify the storm, shown by the image on the right. The surface low sat in a unique position compared to these jet streaks. It was in the exit region of the trailing jet streak, and the entrance region of the leading one. When jets align in this position, it creates winds aloft that diverge and spread apart. That diverging air in the upper levels must be replaced by air rising upward from near the surface, which results in falling surface pressure and a stronger storm.
At the surface, the rapidly falling pressure of the surface low increased the pressure difference, or gradient, between the low and the high pressure over the central United States (image to the right). This caused winds around the low to strengthen. Hurricane-force winds were recorded along the North Carolina coast, and in the Appalachian Mountains, wind gusts over 100 mph were recorded. These extreme winds continued to bring warm, moist air over the Gulf of Mexico northward, and cold, dry air southward, which further amplified the strength of the warm front and cold front.
In the warm sector of the system just ahead of the cold front, where instability is greatest, a potent squall line developed over the Gulf of Mexico and moved across Florida, spawning 11 tornadoes across the peninsula. As cold air continued to plunge southward on the northwest side of the low, several inches of snow fell in parts of the Florida Panhandle. All-time low pressure records were set along the east coast as the storm tracked through the Carolinas and Virginia, with a minimum pressure of 960 mb being reached on Saturday evening when the low was near the North Carolina/Virginia border. As the storm continued up the east coast, it brought widespread snow accumulations of a foot or more to the Appalachians and New England. The National Weather Service noted that “the areal coverage of snowfall was among the largest of any storm in recorded history”, and added together, the total snow volume was almost 13 cubic miles. The storm also had an immense human impact, as it was responsible for nearly 300 fatalities and almost $9 billion in damage, adjusted for inflation.
The weather across East Tennessee on Friday, March 12, was rather unremarkable. Cold air had set into the area behind a cold front, and the day began with a cold rain and temperatures in the mid to upper 30s. With high pressure located east of the Appalachians, and another high located in the central United States, a low pressure trough set up over the area (shown in the first image). This inverted trough would become a key feature that would impact the weather in East Tennessee as the event unfolded on Saturday. It was an area where low level winds converged to enhance rising motion.
The strong northerly winds produced by the tight pressure gradient across the Tennessee Valley supplied cold air that dropped the surface temperature, turning rain into snow through the day on Friday (shown to the right). By the evening, moderate snow was being reported at Tri-Cities, Knoxville, and Chattanooga. The inverted trough continued to linger over the area, locally enhancing rising motions and the intensity of the snowfall. Heavy snow began to be reported in parts of the region on Friday night.
The snowfall intensity was also enhanced by instability underneath the upper level trough. Temperatures in the mid and upper levels of the atmosphere were very cold due to the negative tilt of this trough (previous image), which created unstable conditions. This instability further enhanced the rising motions across the region, and created convective snow bands with very high snowfall rates in excess of one inch per hour.
Even though the storm system was pulling away from the area on Sunday, a northwest wind persisted across the Southern Appalachians, producing an upslope flow that further added to the snowfall amounts in the mountains. The long duration (about 60 hours) and the high rate of accumulation combined to produce unprecedented snow amounts across the region.
Snowfall Climatology Across the Southern Appalachians
The March 13-14, 1993 Storm of the Century is certainly a storm for the record books. Chattanooga and Mount LeConte both set all time single-day snowfall records of 18.5 inches and 30 inches, respectively. Knoxville and Tri-Cities Airport had their 4th highest single day snows of all-time. The extreme snowfall totals also influenced the monthly normal snowfall values for the month of March that is still incorporated in the latest 30-year normals for the period of 1991 - 2020. Chattanooga, for example, has an official normal snowfall of 1.1" in March but has only seen measurable snowfall 4 times in March since 1991. This influence is seen to a similar degree in the 30-year normals in Knoxville and the Tri-Cities, which have recorded more frequent March snowfall in this period but still far below what fell in this event alone.
From a hemispheric/teleconnection perspective, the Arctic Oscillation, Pacific/North American Pattern, and North Atlantic Oscillation were all largely not influential to this specific event as they were all fairly neutral prior to and during the event. With respect to El Nino/Southern Oscillation, ENSO neutral was officially in place during this period of time. However, ocean temperatures did reach +0.5°C to +0.7°C for a limited amount of time which is within weak El Nino strength. While ENSO has fairly limited effects locally, El Nino phase has been loosely tied to below normal temperatures and above normal snowfall, largely due to an extended Pacific jet stream to our south. This was also coincident with an increasingly positive phase of the long-term Pacific Decadal Oscillation (PDO), which has been tied to increased cold and snow in the eastern U.S. via modulation of ENSO conditions. As with any event, it is difficult to tie its occurrence to any teleconnection pattern, but these Pacific SST conditions certainly support favorability for the large-scale pattern that produced the event.
While the snowfall records across a wide swath of not only the Tennessee Valley but a swath of the Eastern United States is impressive, it’s not the only metric we can use to showcase the storm. A key way to estimate the intensity of a storm is by measuring the central pressure. The lower the pressure, the more intense a storm often is. The March 1993 storm ended up with a 960 mb low pressure, comparable to that of a high-end Category 2 hurricane. This shows how extremely low the pressure was and indicative of a potent storm! The image to the right is a map of when in March various parts of the country set their record low pressures. The March 1993 Blizzard's central low set records shown in a red swath from the Big Bend of Florida all the way into Eastern Pennsylvania. Credit: David Roth, WPC.
Snowfall Totals
March 12 - March 14, 1993
The image to the right is a recreation of snowfall totals based on reports at specific points and spatial interpolations. The entire modern-day County Warning Area (CWA) for the Morristown, TN office and surrounding areas received snowfall accumulations that were crippling and even unprecedented in some locations. Most places received at least a foot of snow with multiple feet in the Smokies and the mountains of East Tennessee, southwest Virginia, and southwest North Carolina. Climatologically, some of the most impressive snowfall totals were in the Southern Valley near Chattanooga, where 18" to 24" was reported. Based on modern-day normals, the totals for this storm alone were nearly 10x the normal for an entire year. Most other places received amounts that were significantly higher than yearly normals. As stated in the climatology section, this storm continues to impact climatology in the latest 30-year normals. Also, these values only depict actual snowfall as the drifts from the storm were significantly higher-- several feet in many lower elevation places with 10 to 20 foot drifts in many portions of the mountains.
Tennessee Weather Summary for East Tennessee issued on March 13th by the National Weather Service in Nashville.
All-time 1 day snowfall totals for Chattanooga, Mount LeConte, Knoxville, and the Tri-Cities are on the 4 panel plot to the right. Note Mount LeConte received a 2-day storm total of 60", the heaviest snowfall reported during the cyclone's entire lifespan. For March specifically, this storm shattered Chattanooga's prior monthly record, with the city receiving a storm total of 20", more than 3x greater than the second heaviest snowfall.
Photos & Videos
Video of snow covered streets and plows working in the wake of the blizzard (Courtesy: WATE-TV)
Heavy snow totals and snow drifts left for some challenging commuting conditions within this historic snowfall in the Knoxville area as seen in this video compilation courtesy WVLT-TV .
Aerial view from a helicopter via the Tennessee National Guard during assessment and search and rescue operations. (Courtesy: WATE-TV )
Locations in the Chattanooga area received a storm total snowfall of around 20 inches, the most for any single snowfall event in the Chattanooga area. This story, courtesy of WTVC-TV , reviews this historic storm across southeast Tennessee and north Georgia.
The Chattanooga area definitely "got dumped on", just as former WRCB Local 3 News Chief Meteorologist Paul Barys warned viewers in this Local 3 News archive video footage from the event.
About a foot of snow was observed in Lenoir City with higher drifts due to the wind. This image was taken on Finley Drive in Lenoir City. Randy Freels spent much of the day helping motorists up Highway 321 coming from Broadway.
Front page of the Fentress Courier from March 17th, a few days after the blizzard.
Front page of The Knoxville News-Sentinel from March 14-15, 1993.
Front page of the Watauga Democrat a few days after the Blizzard.
Front page of The Daily Times just after the Blizzard.
