MUWIC Newsletter - April 2002

(Issued: April 2, 2002)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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LEAD STORY: "Winter Ends With a Whimper"

After the second warmest (one of the driest) December through February periods on record, March 2002 ended up "near normal" for both temperature and precipitation. Several late-season blasts of arctic air produced a 12-day stretch of below normal conditions, which ironically occurred around the time of the Equinox. In fact, the "coldest day of the winter" (compared to normal) came on the second full day of Spring when the high and low temperature for the day averaged an impressive 18 degrees below normal. The overall temperature anomaly for the month was +1.4, which falls within the normal range (within 0.75 s.d.) according to our long-term March climatology.

Fortunately, frequent rainfall prevented the drought from worsening in March. Over three inches of rain fell last month-the greatest monthly accumulation since last August-providing significant improvement of surface soil moisture. However, it will take several months of normal to above normal rainfall to bring an end to the severe drought conditions that plague the region. Many streams, reservoirs, and wells remain near record low levels. Follow the links below for the latest drought information.

US Drought Monitor: http://enso.unl.edu/monitor/monitor.html

Seasonal Drought Forecast: http://www.cpc.ncep.noaa.gov/products/expert_assessment/season_drought.gif

PA Stream Flow: http://water.usgs.gov/cgi-bin/dailyMainW?state=pa&map_type=real

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EVENT OF THE MONTH

The nearly one inch of rain (0.95") that fell on March 20th was the largest precipitation event in exactly six months. The last time this much rain fell on the county was September 20, 2001.

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MARCH CLIMATOLOGY

Average High Temp: 52.7 F

Average Low Temp: 32.9 F

Average Monthly Temp: 42.8 F

(Departure from Normal: +1.4 F)

Snowfall: 0.1 inches

(Departure from Normal: -3.9 in.)

Precipitation: 3.09 inches

(Departure from Normal: -0.29)

Annual Precipitation: 5.74 inches

(Departure from Normal: -2.99)

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APRIL NORMALS, RECORDS & FACTS

Normal high/low temperatures range from 57/37 on April 1st to 67/44 by month's end. The record high for April is 95 degrees (on 4/18/76) and the record low is 11 F (on 4/1/23). Normal liquid precipitation (rain and melted snow) is 3.50 inches. Measurable snow falls in April on an average of once every five years. The rainiest April on record occurred in 1983 (9.14 inches) while the driest April was just two years later (0.39 inches in 1985).

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APRIL OUTLOOK

The last three weeks have yielding a significant change in the jet stream pattern across North America with a mean trough located in the eastern half of the country and an enhanced storm track in our region. Temperatures averaged below normal from the Northern Plains to the Mid-Atlantic coast, and near-normal precipitation fell on the drought-stricken areas east of the Appalachians. As we progress into April, the big question relates to whether this pattern continues or reverts to the warmer, drier configuration of past months.

My sense is that we will continue to see a mean trough near the East coast in the short-term. Although there will be a warm day every now and then, I expect there to be more below normal days than above normal through the first week to ten days. There could also be a couple rounds of measurable rainfall, possibly on April 3rd and around April 8th.

By mid-month, the mean trough position may shift off the east coast allowing Pacific air to return to the eastern states. If so, cold intrusions from Canadian would be limited in length and magnitude, and a turn to increasingly warm conditions would result. In such a pattern, precipitation would tend to be less organized and more showery. Hopefully, we'll get more than our share of April showers this year; though, I would tend to lean towards a slightly drier than normal month when it's all said and done.