MUWIC Newsletter - March 2007

(Issued: March 2, 2007)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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LEAD STORY: A Winter of Extremes

The winter of 2006-2007 will be remembered for the sharp contrast of extremes that it served up across the northeast quarter of the country. Meteorological winter is the three-month period of December, January, and February (the three coldest months of the year), and this time around it featured two dramatically different and nearly equal-length parts. The period from December 1^st through January 16^th produced sustained warmth and virtually no snowfall. A mid-January reversal in the jet stream pattern then shifted temperatures to below-normal levels that would persist through the end of February.

While variability is a hallmark of Lancaster winters, this season was especially remarkable because of the magnitude and duration of the temperature extremes. Consider that January’s average temperature was 35.6 degrees or 5.5 degrees above normal, while February’s average temperature was 25.5 or 7.2 degrees below normal (and the coldest since 1979). Only once before (1934) has there been such a large temperature differential between the months of January and February. Another metric of the contrast: January was the twelfth warmest on record, while January was the sixth coldest.

The Two Faces of Winter 2006-2007:

Dates Duration Depart. from Norm Snowfall

Dec. 1, 2006 – Jan. 16, 2007 47 days +8.8 Trace

Jan. 17, 2007 – Feb. 28, 2007 43 days -5.9 12.4”

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STAT OF THE MONTH

The Valentine’s Day “snowstorm” will be remembered more for the large amount of ice that fell. In addition to the 5-inch snowfall, nearly 2.5 inches of sleet fell across the region. Not since the Blizzard of 1993 has so much sleet fallen in the Lancaster area.

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FEBRUARY CLIMATOLOGY (MU Weather Station)

Average High Temp: 32.9 F

Average Low Temp: 18.1 F

Average Monthly Temp: 25.5 F

(Departure from Normal: -7.2 F)

Snowfall: 11.4 inches

(Departure from Normal: +3.2)

Total Precipitation (liquid equivalent): 2.40 inches

(Departure from Normal: -0.07)

Annual Precipitation: 4.73 inches

(Departure from Normal: -0.75)

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MARCH NORMALS, RECORDS & FACTS

Normal high/low temperatures increase rapidly from 46/26 on March 1st to 59/36 on the 31st. The record high for March is 88 degrees (1921, 1945) and the record low is –1 F (1984). Normal liquid precipitation (rain and melted snow) is 3.38 inches. Average snowfall for the month is 3.7 inches. Spring officially arrives at 7:07 p.m. on March 20^th.

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MARCH OUTLOOK

March is beginning as February ended; that is with an icy snow cover and a jet stream blocking pattern that helps anchor cold air across the Northeast. As I write this outlook, however, a large storm raging in the Plains may be planting the seeds of a pattern change. While the first seven days of March look to continue the below-normal trend of February (despite a warm day on March 2^nd), a breakdown of the blocking pattern across eastern Canada is signaling a turn to milder weather beginning around March 8^th.

Still, there is a tremendous snow pack across Canada and a reservoir of cold air lingers in the Arctic. Given jet stream amplification in the eastern US or a return of high-latitude blocking across eastern Canada, I would expect another period of below-normal weather and perhaps a final round of snow sometime during the mid-month. March often yields some wild swings in temperature and a big storm or two, and this may be the case this year. In the end, however, I expect that March will conclude within a few degrees of normal with a near-equal number of above and below normal days.