MUWIC Newsletter - January 2006

(Issued: January 4, 2006)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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LEAD STORY: “Cold, Snowy Start to Winter”

Although winter doesn’t officially begin until December 22^nd, meteorologists often consider December 1^st as the beginning of winter given that December, January, and February are the three coldest months of the year. The first few weeks of December 2005 fit this seasonal model perfectly as temperatures averaged 8 degrees below normal through December 21^st. Ironically, the official start of winter brought the beginning of a ten day “holiday thaw” with temperatures averaging 6 degrees above normal. In aggregate, the month concluded 3.6 degrees below normal—the 20^th coldest December on record (out of 92 years).

December also brought greater-than-average snowfall with a total of 8.4 inches. Most of this snow occurred with a fast-moving storm on December 9^th. Six inches fell here in Millersville, but up to a foot of snow was reported in extreme northern Lancaster county near Brickerville.

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EVENT OF THE MONTH

Bitter chill settled over the area on December 14^th with a morning low temperature of 0 degrees. This is the earliest in the winter season that a zero degree reading has been recorded.

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STAT OF THE MONTH

The period December 1^stto the 15^th averaged 10.1 degrees below normal. This is the coldest first-half of December on record.

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DECEMBER CLIMATOLOGY (MU Weather Station)

Average High Temp: 37.7 F

Average Low Temp: 23.1 F

Average Monthly Temp: 30.4 F

(Departure from Normal: -3.6 F)

Snowfall: 8.4

(Departure from Normal: +3.8 inches)

Total Precipitation: 3.16 inches

(Departure from Normal: +0.18)

Annual Precipitation: 38.83 inches

(Departure from Normal: -2.19)

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JANUARY NORMALS, RECORDS & FACTS

Normal high/low temperatures for January are 39/22, respectively. The record high for the month is 77 degrees (January 27, 1950) and the record low is -18 (January 21, 1994). Normal liquid precipitation (rain and melted snow) is 3.01 inches. Average snowfall for the month is 8 inches.

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JANUARY OUTLOOK

January begins as December ended: mild and damp. The first week of January will average several degrees above normal, so you might consider this is our “January Thaw.” Enjoy it while it lasts, however, because I do think we’ll see a turn to more wintry weather for mid-month and beyond. An active Pacific jet stream is sending a parade of storms into the West coast (per recent flooding), and it’s these systems that often seed development of East coast storms. Therefore, I expect above normal storminess and precipitation for the month ahead.

Snow lovers, then, are wondering, “where’s the cold air?” For the time being, the core of the arctic air is in the arctic, although a gradual press southward looks to begin around January 7^th. I do not see dramatic turn to below-normal conditions, but instead a gradual return to near-normal temperatures for January 7 to 14^th. With marginal cold air in place during this time frame, I’d expect a mixed-bag type storm to deliver snow, sleet, and rain to the Commonwealth sometime during the second week of January.

The trend for the second half of the month will depend on the direction of the North Atlantic Oscillation (NAO). With an active Pacific flow likely to continue, a neutral or positive NAO will result in more rain than snow and a trend back above normal with temperatures. If the NAO dips negative—and there are signs this will happen after January 15^th—then the second half of January could be a replay of what we experienced in early December. My sense is that we will not experience any record cold in January, however, the may be just enough snow and cold to result in near-normal temperatures and snowfall by month’s end.