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As noted previously, by the time blocks have retrograded to the Hudson Bay, odds are against the development of a Kocin-Uccellini snowstorm in late February through March. Nonetheless, there is one exception, which I have brought up in a number of posts: the long-duration February 22-28, 1969 snowstorm, which occurred during a pattern of frequent snowfalls. This storm deserves greater attention given the continuing evolution of the overall pattern and on account of the CPC analogs centered around 3/7 bringing up February 25, 1969 (per 0z GFS, 6z ensembles, ensemble composite) and February 24, 1969 for the date centered around 3/10.
That storm brought its heaviest snows to New England. Amounts included:
Mount Washington: 97.8”
Pinkham Notch, NH: 77.3”
Long Falls, ME: 56.0”
Boston: 26.3”
Philadelphia: 1.9”
New York City: 1.3”
In the wake of this storm, another system brought snowfall to the Mid-Atlantic and New England states on March 1-3. Amounts included:
Boston: 5.1”
Philadelphia: 4.4”
Washington, DC: 4.2”
New York City: 2.8”
On March 7, yet another storm brought additional snow to some of these cities:
Philadelphia: 4.0”
New York City: 2.8”
Washington, DC: 2.0”
The latest ensemble means suggest that the East is evolving into a snowy period. Indeed, arguably that period commenced with the 2/25-26 clipper that brought accumulating snow to parts of New England. By 3/7 0z, the forecast 500 mb pattern bears some similarities to that at the onset of the February 1969 snowstorm.
February 24, 1969 Charts:
NCEP ensemble mean 500 mb height anomalies for 3/7 0z:
The February 1969 snowstorm was characterized by at least the following:
∙ absence of a cutoff ridge in Greenland
∙ moderate intensity
∙ erratic intensification
∙ long duration
∙ after reaching the waters of southeast New England, the surface low remained in that vicinity from 2/25 through 2/28
Source: Paul J. Kocin and Louis W. Uccellini, Northeast Snowstorms, Volume II: The Cases, Boston: American Meteorological Society, 2004, pp.459-460.
If one is looking for a KU-type snowstorm in the March 1-20 period, Miller A and Miller B systems are equally likely. The breakdown for such KU storms was:
Miller A:
March 18-21, 1958
March 12-14, 1993
Miller B:
March 18-20, 1956
March 2-5, 1960
Source: Paul J. Kocin and Louis W. Uccellini, Northeast Snowstorms, Volume I: Overview, Boston: American Meteorological Society, 2004, pp.53-54.
Miller A systems have, on average, brought Washington, DC 4” or more snow. Miller B’s have seen the accumulations range from 1.7” to 7.9”. Philadelphia has done well with Miller B systems (8” or more) and best with Miller A systems (10” or more). New York City has received 10” or more from all four systems, but seen somewhat larger snowfall from Miller B storms. Boston has done best with Miller B systems (12” or more).
Although none of these storms brought Washington, DC 10” or more snow, earlier storms i.e., March 26, 1891 and March 29-30, 1942 have done so.
Miller A Snowfall Amounts:
Boston:
March 1958: 6.7”
March 1993: 12.8”
New York City:
March 1958: 11.8”
March 1993: 10.6”
Philadelphia:
March 1958: 11.4”
March 1993: 12.0”
Washington, DC:
March 1958: 4.6”
March 1993: 6.6”
Miller B Snowfall Amounts:
Boston:
March 1956: 13.2”
March 1960: 19.8”
New York City:
March 1956: 11.6”
March 1960: 14.6”
Philadelphia:
March 1956: 8.7”
March 1960: 8.4”
Washington, DC:
March 1956: 1.7”
March 1960: 7.9”
CPC Analogs:
The latest CPC analogs centered around March 7 are:
March 23, 1958 (2X), March 24, 1958, March 5, 1962 (3X), February 23, 1966 (2X), February 25, 1969 (3X), March 24, 1972, February 25, 1981, March 19, 1987, and March 11, 1999.
Snowfall of 0.1” or more occurred +/- 3 days from each of these cases the following percentage of time:
Boston: 100%
New York City: 78%
Philadelphia: 78%
Washington, DC: 67%
If one only employs those that were cited 2 times (2X) or more, such snowfall occurred the following percentage of time:
Boston: 100%
New York City: 100%
Philadelphia: 100%
Washington, DC: 75%
Conclusion:
Per historical snowfall data and the ENSO region anomalies/MEI, I believe March 2006 will feature above normal snowfall from Washington, DC (DCA) to Boston and perhaps into the Ohio Valley. Philadelphia/NYC to Boston might have the largest departures from normal. One can get there without a KU snowstorm e.g., March 1967. More details on the March’s snowfall potential will be provided in my March 1-15 pattern discussion tomorrow.
Given the moderate block that is likely to be retrograding slowly toward the Hudson Bay, the March 1-10 period could feature one or more snow events. While odds favor more moderate events than a full-fledged KU storm, the synoptic situation seems to be evolving somewhat more toward something along the lines of the February 1969 system discussed above. Hence, such a storm should not be ruled out. A possible timeframe for such an event would be the March 6-8 period.
If one examines the upper air charts for the February 1969 system and the forecast situation around March 7 0z, one should be wary of possible model attempts to crush any possible storms in that timeframe to the south. Odds strongly favor an impact on at least the eastern half of New England and perhaps even farther to the south and west.
Prior to this event, another system could bring a moderate snowfall to southern and especially central New England, including Boston, around 3/2. A light accumulation is still possible in New York City and perhaps even Philadelphia. However, the ECMWF’s more northward track is as plausible as the recently more suppressed GFS ideas. That storm should bring Boston’s 2005-06 seasonal snowfall above 40”. New York City should reach 40” or more for the season before the first 10 days of March are finished and Philadelphia should surpass 20” for the season by that time.