MUWIC Newsletter - May 2005

(Issued: May 3, 2005)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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MONTH IN REVIEW: “April Showers Yield to Notable Dry Spell”

April began and ended on a wet note, while mid-month featured a surprising lack of April showers. Over two inches of rain fell during the first three days of April, but save a few showers on the 7^th and 8^th, the next significant rain did not occur until April 22^nd. The twelve consecutive days with no precipitation came up short of the record seventeen-day dry spell in April 1942, but it did rank as the eighth-longest, sans-rain period on record in April.

Following the coldest March in a decade, temperatures turned much warmer in April with an average daily anomaly two degrees above normal. Two dramatic “summer previews” unfolded on April 6^th (high of 83F degrees) and the 19^th and 20^th (high of 84F both days). The month ended with a cool, damp spell and even some patchy frost on morning of the 25^th.

View the complete MUWIC climate summary at:

http://www.atmos.millersville.edu/~cws/data-new/2005/apr2005.htm

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EVENT OF THE MONTH

One of the strongest Spring storms in recent years dropped heavy rain and snow across the Commonwealth on April 2^nd and 3^rd. Heavy snow in northwestern PA accumulated up to 29 inches in Erie county, while 2 to 4 inches of rain fell across much of central and eastern PA. Follow the links below to view maps of rainfall and snowfall for this storm (National Weather Service).

Snowfall map:

http://www.erh.noaa.gov/ctp/features/2005/AprilFlood/04_03_2005.gif

Rainfall map:

http://www.erh.noaa.gov/ctp/features/2005/AprilFlood/2dayprecip.png

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APRIL CLIMATOLOGY (MU Weather Station)

Average High Temp: 65.4 F

Average Low Temp: 42.4 F

Average Monthly Temp: 53.9 F

(Departure from Normal: +2.0 F)

Snowfall: Trace

(Departure from Normal: -0.3)

Precipitation: 3.76 inches

(Departure from Normal: +0.29)

Annual Precipitation: 12.60 inches

(Departure from Normal: +0.27)

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MAY NORMALS, RECORDS & FACTS

Normal daily temperatures will shoot up 9 degrees this month. The normal high/low ranges from 70/44 on May 1st to 79/54 by month’s end. The record high for May is 98 degrees (on 5/23/25) and the record low is 27 F (on 5/1/78). Normal monthly rainfall is 3.62 inches. The rainiest May on record occurred in 1989 (10.07 inches) while the driest May was in 1939 when just a half-inch fell.

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MAY OUTLOOK

Many years, the weather pattern in May kicks into a summer-like configuration and warm weather abounds for much of the month. May 2004 was a classic example of this, as high temperatures reached the 80s on 16 days and once reached 90F. I do not expect such enduring warmth this May, but instead brief warm spells punctuated with backdoor cold fronts that drop temperatures below normal for a couple days. Consequently, temperatures for the month ahead may average out near normal.

It will be a different story from the Southern Plains to the Tennessee Valley, where I expect more persistent warmth and a high likelihood of above normal conditions. It’s this warmth that will expand eastward from time to time. One such surge of warmth into the Mid-Atlantic may occur around May 9^thor 10^th—if so, local high temperatures could reach the 80-degree mark for a day or two. However, a large area of unseasonably cold air remains in place over eastern Canada and the current jet stream pattern favors occasional discharges of this cool air into the Northeastern US. The cold air will arrive on the wings of fronts dropping south from Ontario and Quebec (a.k.a. backdoor cold front). Thus, a balmy day in the low 80s may be followed by a couple days with highs only in the 60s.

Such a pattern should produce more dry days than rainy days, possibly at the rate of three-to-one. One caveat is that as May progresses, we are climatologically more favored for receiving severe thunderstorms. So, although the month ahead may be somewhat lacking in rainfall, it’s still possible that we could experience a memorable thunderstorm or two.