MUWIC Newsletter - January 2002

(Issued: January 8, 2002)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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LEAD STORY: "Third Warmest December on Record"

Despite a bitterly cold New Year's Eve, December 2001 will be remembered for its unusual warmth. In aggregate, the month was 6.7 degrees above normal and, thus, the third warmest December on record. The warmest December of record was 8.5 degrees above normal (set in 1923).

An impressive jet stream ridge along the eastern seaboard combined with parched ground conditions to skyrocket temperatures during the first week of the month. This seven-day period averaged a remarkable 15 degrees above normal making it the warmest December week on record. The second and third weeks of December were less dramatic, but still notable, at over 8 degrees above seasonal averages. Not until the last ten days of the month did winter chill finally arrive in the region. The final ten days of December averaged about 2.5 degrees below normal.

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EVENT OF THE MONTH

The high temperature of 78F on December 5th was the warmest December day on record in Lancaster. Our climatological database dates back to 1914.

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STAT OF THE MONTH

We have been tracking the developing drought for months, but it is now official--2001 ended up as the driest year on record in the Lancaster area. The total precipitation for the year was just 22.68 inches; that's over 18 inches below normal and only 55 percent of normal precipitation for the year. The old record low amount of annual precipitation was 26.01, set in 1930.

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DECEMBER CLIMATOLOGY (MU Weather Station)

Average High Temp: 49.0 F

Average Low Temp: 30.8 F

Average Monthly Temp: 39.9 F

(Departure from Normal: +6.7 F)

Snowfall: Trace

Precipitation: 1.01 inches

(Departure from Normal: -1.97)

Annual Precipitation: 22.68 inches

(Departure from Normal: -18.38)

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JANUARY NORMALS, RECORDS & FACTS

Normal high/low temperatures for January are 37/21, 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 10 inches.

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JANUARY OUTLOOK

Since this monthly outlook is being issued one week into the month (due to my vacation over New Year's), you might expect the task at hand to be easier than normal. In fact, the "challenge index" remains "high" as an increasingly unsettled pattern continues and arctic air is poised to the north and "ready to go." Odds are good that this January will feature more wintery weather as well as some major forecast problems for meteorologists.

In the near-term, Pacific air will overtake the region and allow temperatures to warm into the 40s on several occasions through mid-month. However, we'll have to keep an eye out for any upper-level system tracking by to our south that might trigger the development of a low pressure system. With plentiful cold air available to our north, any such system can pull in enough sub-freezing air to change rain to snow--as we on Sunday (1/6)--despite high temperatures that are a few degrees above normal ahead of the storm. One such threat could occur this Friday (1/11) and, maybe, again by late next week.

Temperature-wise, the first week of the month averaged a degree or two below normal, and I expect the next 7 to 10 days to average a couple degrees above normal (i.e. due to Pacific air masses mentioned above). However, a strong push of arctic air looks likely for later this month, possibly as early as the end of next week. If so, the coldest air of the season could arrive around January 20th (give or take a few days) and more snow could follow before month's end.