A Study of Major Snowstorms for Raleigh, NC

**Updated 11/8/04**

The 20 dates and their approximate snow accumulations at the airport, used for Raleigh were: 
Feb 26-27 2004              6.5 inches 

Jan 2-3 2002	           10.8 inches 

Jan 24-25 2000             20.3 inches 

Feb 17-18 1989              6.2 inches 

Jan 7 1988	            7.3 inches 

Feb 6 1984	            6.9 inches 

Mar 24 1983	            7.3 inches 

Jan 13-14 1982	            6.0 inches 

Mar 1-2 1980	           11.1 inches 

Feb 18 1979	           10.4 inches 

Jan 7-8 1973	            6.4 inches 

March 1 1969	            9.3 inches 

Feb 9 1967	            9.1 inches 

Jan 25-27 1966	            9.7 inches 

Feb 26 1963	            6.9 inches 

March 9-10 1960	            7.0 inches 

March 2-3 1960              7.1 inches 

Dec 11 1958	            9.1 inches 

Jan 19 1955	            9.0 inches 

Feb 1 1948	            6-7 inches

The following are the 10 mean surface maps for the 10 time periods stated earlier.
  • Mean SLP 12 hours before precip starts
  • Mean SLP 6 hours before precip starts
  • Mean SLP around start of precip
  • Mean SLP between start of precip and peak of precip
  • Mean SLP around peak of precip
  • Mean SLP between peak of precip and end
  • Mean SLP around end of precip
  • Mean SLP 6 hours after end of precip
  • Mean SLP 12 hours after end of precip
  • Mean SLP 18 hours after end of precip

    This map shows the track of the surface low:
  • Track of the mean sea level pressure low

    The track of the low shows that it is further east of the ideal track scenario for Hickory, tracking a little further south across Florida and then a little further east off the coast, as would be expected.

    Here are the mean precip maps:
  • Mean precip 12 hours before precip starts
  • Mean precip 6 hours before precip starts
  • Mean precip as precip starts
  • Mean precip between when precip starts and peak
  • Mean precip at peak
  • Mean precip between peak and end of precip
  • Mean precip at end of precip
  • Mean precip 6 hours after end of precip
  • Mean precip 12 hours after precip starts
  • Mean precip 12 hours after precip starts

    An interesting observation is that even less significant precip moves north in the Raleigh ideal low track. As there is very little north of southeast Virginia. I was expecting more precip up the mid-atlantic and into the northeast.

    The following 5 figures are the mean NH 500mb pattern:
  • NH Mean 500mb 12 hours before precip starts
  • NH Mean 500mb 6 hours before precip starts
  • NH Mean 500mb around start of precip
  • NH Mean 500mb peak of precip
  • NH Mean 500mb around end of precip

    This is the NH 500mb anomalies for the peak days. Notice the placement and strength of the anomalies. There is actually a weak negative anomaly over southern Greenland, which is odd as one would usually assume a Greenland Block was present during significant snowstorms this far south. The three most notable features, other than the negative anomaly over the Tenn valley associated directly with the storms, are 1.) A strong negative anomaly east of Newfoundland in the famed 50/50 low area. 2.) A strong positive anomaly over eastern Alaska and the NW portion of the NW Territories in Canada and into the Beaufort Sea. 3.) A low anomaly in the western most Aleutian Islands. These are the three features one must look for on average, for a major eastern NC snow event climo wise.
  • NH 500mb Anomalies

    The following 5 figures are the mean US 500mb pattern:
  • USA Mean 500mb 12 hours before precip starts
  • USA Mean 500mb 6 hours before precip starts
  • USA Mean 500mb around start of precip
  • USA Mean 500mb around peak of precip
  • USA Mean 500mb around end of precip

    One can see the prevalent 500 mb features are very similar to the ones for the Hickory pattern. A very strong positive anomaly over Alaska creating cross-polar flow. The -NAO feature is very diffuse if non-existent, and obviously this could just be a few events with positive NAO's balancing out a general negative NAO but the event is none the less interesting and shows that for Raleigh to get big snows, the NAO does NOT have to be raging negative.

    THe following fields are the 850mb heights showing us the track of the 850 low.
  • 850mb Heights 12 hours before precip begins
  • 850mb Heights 6 hours before precip begins
  • 850mb Heights around when precip begins
  • 850mb Heights between when precip begins and the peak
  • 850mb Heights around peak of precip
  • 850mb Heights between peak and end of precip
  • 850mb Heights around end of precip

    The following fields are the 300mb winds showing what type of jet stream configuration was present.
  • 300mb Winds 12 hour before precip begins
  • 300mb Winds 6 hour before precip begins
  • 300mb Winds around when precip begins
  • 300mb Winds between when precip begins and peak
  • 300mb Winds around peak of precip
  • 300mb Winds between peak and end of precip
  • 300mb Winds around end of precip
    One can see that there was a mean 55-60 m/s (~110-120 kt) jet streak from the mid atlantic to just off shore. This would make sense because it would mean the area of the Gulf coast was in the favorable right front entrance region of the upper level jet streak, thus making it a favorable area of upward motion and low pressure development.

    Next I plotted 1000mb, 850mb, 700mb, and 500mb heights for NC and attempted to get mean thickness values and heights for this type of weather scenario for Raleigh. The following was noted:

    12 hours before precip:
    1000-850mb thickness (m) 1291
    850-700mb thickness (m) 1533
    1000-500mb thickness (m) 5398
    850mb T (C) -3

    6 hours before precip:
    1000-850mb thickness (m) 1289
    850-700mb thickness (m) 1536
    1000-500mb thickness (m) 5399
    850mb T (C) -3

    Precip Begins:
    1000-850mb thickness (m) 1286
    850-700mb thickness (m) 1533
    1000-500mb thickness (m) 5395
    850mb T (C) -3

    Between beginning and peak of precip:
    1000-850mb thickness (m) 1291
    850-700mb thickness (m) 1535
    1000-500mb thickness (m) 5405
    850mb T (C) -2.5

    Peak of precip:
    1000-850mb thickness (m) 1292
    850-700mb thickness (m) 1535
    1000-500mb thickness (m) 5399
    850mb T (C) -2.5

    Between peak and end of precip:
    1000-850mb thickness (m) 1290
    850-700mb thickness (m) 1533
    1000-500mb thickness (m) 5384
    850mb T (C) -3

    End of precip:
    1000-850mb thickness (m) 1289
    850-700mb thickness (m) 1526
    1000-500mb thickness (m) 5360
    850mb T (C) -3.5

    An intersting note here is that Raleigh has mostly lower thickness values for the entire duration as compared to Hickory. This is probably just showing an air mass of arctic origin on average is needed for a significant snow storm in Raleigh.

    Some conclusions for Raleigh:
    1. The 500mb pattern most common in these 20 events is one where there is pronounced ridging over and above Alaska and also in western North America leading to cross-polar flow and a +PNA configuration, but unlike Hickory, the -NAO signature is very diffuse and much less than what is shown in the Hickory data. This could indicate the ideal pattern for big RDU snows is a strong +PNA configuration and a transitional NAO pattern where the value is around neutral.
    2. The mean 500mb height values were in general were between 5570-5600m just prior to snowfall, during the height of the storm the values were generally 5480-5550m.
    3. The mean 1000-500mb thickness values were around 5390-5405m for most of the storm. The mean 1000-850mb thickness values were between 1286-1292m throughout the storm. The mean 850-700mb thickness were around 1533-1536m througout the storm.
    4. The mean track of the surface low as demonstrated above is from the central Gulf, the northern FL peninsula (further south than the Hickory track), and then approximately 100-150 miles off of the southeast coast (further east than Hickory).
    5. Most storms that effect eastern NC with heavy snow, will not effect areas north of southeast VA and the lower Delmarva with heavy precip.