PD1 Feb 17-19 1979 Study



Updated 5/20/05

Overview of the Storm


The storm that affected the southern and eastern US on Feb 17-19 1979 is commonly referred to as the Presidents Day Storm. This was a remarkable storm that brought wintry weather to many parts of the country from Alabama to the NE US. For another read on the storm please read Uccellini and Kaiser (1985) in the Monthly Weather Review Vol 113. This is a great paper, that has some satellite images from the storm, and it examines the role of a tropopause fold during the storm, and gives a more technical description of the storm than what I do here. You can find the paper here Uccellini and Kaiser 1985

The storm was the final blow to a period of very cold weather across the US. The NAO averaged negative according to the CPC for December (-2.934), January (-2.032), and February (-1.511), but switched to positive following this storm. Below are the NH 500mb maps for 00z Feb 17th, 00z Feb 18th, and 00z Feb 19th.
1 2 3

Below is a table with selected snow accumulations for part of the south. These data were gathered from NCDC.

Snowfall for some SE cities
City, State Snow (inches) City, State Snow (inches) City, State Snow (inches) City, State Snow (inches) City, State Snow (inches)
Boone, NC 16.5 Florence, SC 11 Toccoa, GA 10 Chattanooga, TN 5.6 Muscle Shoals, AL 2.7
Hickory, NC 11 Rock Hill, SC 9 Atlanta, GA 4.2 Knoxville, TN 5.1 Hunstville, AL 1.4
Raleigh, NC 10.4 Greenville/Spartanburg, SC 8.2 Athens, GA 3.5 Nashville, TN 5.1
Charlotte, NC 10 Anderson, SC 5.7 Macon, GA 3.4 Memphis, TN 2.7
Charloote, NC 10 Columbia, SC 5.5 Augusta, GA 3.4
Greensboro, NC 9.3 Orangeburg, SC 3.8
Asheville, NC 8.6 Charleston, SC 1.7
Pope AFB, NC 8.5
Rocky Mount, NC 7.5
Elizabeth City, NC 6
Wilmington, NC 0.2

The storm began as a 500mb s/w that rotated onshore in Washington State around a major Gulf of Alaska low in a -EPO pattern. The s/w skirted the Northern Great Plains and then dropped in the Missouri Valley and moved across the Ohio Valley and Mid-Atlantic states Feb 17-19. The s/w eventually closed off over the Mid-Atlantic and brought record-breaking snows to the DC/Baltimore area. Also notice the 500mb s/w racing thru the NE US on the 17th that was accompanied by a very cold air mass that will be shown later. These progressions can be seen below in the below 500mb Heights vs Vorticity sequence.

Feb 17th 00z

Feb 17th 12z

Feb 18th 00z

Feb 18th 12z

Feb 18th 18z

Feb 19th 00z

Feb 19th 06z

Feb 19th 15z


I have also included maps obtained from the NOAA Central library NOAA central library for these dates.

Feb 17th Feb 18th
Feb 19th

Now lets look at maps of the surface pressure and 850mb temperatures. I have made a sad attempt to draw in surface fronts and pressure centers on my images, so bear with me. First of all on 00z on the 16th, we can see the very cold air mass and very strong arctic surface high (1050mb+) moving into the northern US, with 850 T's 0f -28C over the Dakotas and the arctic front near the Miss River valley. Temps were warm across most of the southeast on the 15th, Raleigh had a high of 72 that day. The front blasts off the east coast by 00z on the 17th, with the cold air pouring south and very windy and cold conditions across the NE. You can also see the surface high pressure sliding into the Great Lakes region, and a Cold Air Damming configuration to the isobars east of the mountains begins to show up. Also notice the inverted trough (black dotted line) that forms across the gulf coast and leads to precipitation breaking out there. A wintry mix was falling across northern Miss and AL by the evening of the 17th. By 12z on the 18th, a coastal front is developing off the Carolina coast and would later serve as the focal point for the development of the main surface low. Keep in mind this reanalysis data, is a gridded data set of the actual observations and other data, thus it will miss some of the mesoscale features and also underestimate the strength of the cold air and the surface lows. On the 18th most of the Carolinas and northern Georgia are below freezing, with snow and ice falling. I have included the NARR model predicted 3 hour precip, which as with any model even at 3 hour predictions isn't perfect, and the model estimated surface freezing line, indicated by the blue line. Again keep in mind the reanalysis grid was too warm with surface temps but can get the idea. If you look above at the NOAA Library map you can see the actual ground truth, and you can see that at 7am (12z) on the 18th, freezing rain is falling as far south as Savannah, GA. Temps in the Carolinas are in the teens to low 20s, while most of Ga is in the 20s.
Feb 16th 00z Feb 17th 00z
Feb 17th 12z Feb 18th 00z
Feb 18th 06z Feb 18th 12z
Feb 18th 18z Feb 19th 00z
Feb 19th 06z Feb 19th 12z
Feb 19th 18z

The 3 hour NARR reanalysis predicted precip vs surface freezing line (blue line.)
Feb 18th 06z Feb 18th 09z Feb 18th 12z
Feb 18th 15z Feb 18th 18z Feb 18th 21z

Here are the NARR soundings for RDU. Notice the extreme cold air in the lower atmosphere near the surface, and also notice the warm nose come in by 3z on the 19th which helped mix ice in with the snow at RDU.
Feb 18th 12z Feb 18th 18z Feb 19th 03z
Feb 19th 06z

In this situation, we do see an strong arctic air mass move into a very favorable position for wintry weather across the southeast, but we see the main s/w tracking further north than usual. However, the s/w does the job of turning the winds aloft southwesterly and producing an overrunning setup. Now couple that with the extremely strong temperature gradient between the very cold land and the relatively warm ocean water, and we see a coastal front develop. As the s/w digs we see PVA (positive vorticity advection) commence over the coastal boundary, and thus a surface low begins o form just off the SC coast which led to a period of enhanced snow over eastern NC the afternoon of the 18th, but also led to a mixing with freezing rain and sleet as the precip ended and the warm advection just above the surface came in. Here are the observations for RDU for the storm.

Storm Observations for RDU for Feb 18th and 19th
Time Weather Temp (F) Winds Visibility
7am Light Snow 14 NNE 14kt 2.5 miles
8am Moderate Snow 13 NNE 14kt 0.5 miles
9am Moderate Snow 12 NE 14kt 0.5 miles
10am Moderate Snow 12 NNE 15kt 0.5 miles
11am Moderate Snow 13 NNE 11kt 0.38 miles
Noon Heavy Snow 13 NNE 11kt 0.25 miles
1pm Heavy Snow 13 NNE 11kt 0.25 miles
2pm Heavy Snow 14 NNE 9kt 0.12 miles
3pm Heavy Snow 14 NE 11kt 0.12 miles
4pm Heavy Snow 14 NE 9kt 0.12 miles
5pm Heavy Snow 14 NE 10kt 0.12 miles
6pm Heavy Snow 14 NE 11kt 0.12 miles
7pm Moderate Snow 14 N 11kt 0.5 miles
8pm Light Snow 13 NNW 9kt 5 miles
9pm Light Sleet mixed with Snow 13 NNW 10kt 2.5 miles
10pm Light Freezing Rain mixed with Snow 14 NNW 11kt 1 miles
11pm Light Freezing Rain mixed with Snow 13 NW 13kt 1 miles
Midnight 2/19 Light Freezing Rain mixed with Snow 12 NW 14kt 2.5 miles
1am 2/19 Light Snow 12 NW 11kt 2 miles
2am 2/19 Light Snow 13 NW 16kt 2 miles
3am 2/19 Light Freezing Drizzle 15 NW 10kt 2 miles
4am 2/19 Light Freezing Drizzle 17 NW 11kt 5 miles

Next lets look at the 250mb winds for 6z, 12z, and 18z on the 18th. Notice that the 160kt jet streak over the Mid-Atlantic, which places the Mid-Atlantic and southeast in the favorable Right Rear Entrance region of the jet streak, where rising motion is maximized.
Feb 18th 06z Feb 18th 12z Feb 18th 18z

Couple that with what the 850mb maps show. The following figures show the 850mb heights and winds from 6z on the 18th thru 12z on the 19th. Notice the increase in the 850mb winds, (low level jet), in the morning hours of the 18th. We see a 50 to 60kt jet streak propagate across Georgia and the Carolinas. Near this low level jet, especially in the areas where the upper level divergence was increased due to the upper level jet, vertical motions were enhanced. Also notice that a 850mb low never closes off until 12z on the 19th, and this is what helped lead to the heavy snow in the Mid-Atlantic region.

Feb 18th 06z Feb 18th 12z Feb 18th 15z
Feb 18th 18z Feb 18th 21z Feb 19th 00z
Feb 19th 03z Feb 19th 06z Feb 19th 12z
Feb 19th 15z
A look at the 850mb heights on a smaller contour interval of 10m, along with the convergence at 850mb, shows the low level forcing that was driving the precip over the southeast. Notice at 12z on the 19th, the high values of convergence over the DC, southern NJ, and Delaware area, coinciding with the heavy snow there.

Feb 18th 12z Feb 18th 18z Feb 19th 12z

The following figures are vertical cross-sections from Birmingham, Al to Norfolk, VA from 9z on the 18th to 6z on the 19th. You can see the upward motion, (negative omega), progress across the region.
Feb 18th 9z Feb 18th 12z Feb 19th 15z
Feb 18th 18z Feb 19th 00z Feb 19h 3z
Feb 19th 6z

So all and all this was a very memorable storm, especially for areas in the Mid-Atlantic in the northern Va to NJ corridor. But it had plenty of memorable this far south as well, as there was large area of heavy snowfall across the Carolinas and northern Ga. Again for a more technical synopsis of this event refer to the Uccellini Kaiser 1985 paper, among others. Hopefully this was helpful and informative.