The fourth month of the year was another dry one, as all the major reporting cities except Pittsburgh were about an inch or more below the average monthly precipitation. In the end, temperatures were slightly above average, but that represents a balance between a few spells of both cool and warm weather.

April 2001 began cool and cloudy, with scattered showers on the first of the month. The second was fairly dry and continued cool, with most of the state topping out in the mid to upper 40's, but the Scranton area only reached 39 as some cold air remained lodged in the northeastern part of the state. A small but occasionally heavy patch of rain swept northwest to southeast through the state on the afternoon of Tuesday the 3^rd.

The sun came out on Wednesday the 4^th and temperatures started to climb back towards normal. The fifth was another dry and mild day, with the western part of the state getting most of the warmth. A front came through on Friday the 6^th with a round of respectable showers. Most of the state ended up with a couple tenths of an inch of rain, but Pittsburgh hit the jackpot with over an inch.

During the 7^th and the 8^th, a nearly stationary front divided the state so that the eastern half remained relatively cool while the west got an early taste of summer. A few disturbances along the front gave us occasional showers. The front finally pushed east by early on Monday the 9^th, allowing just about the whole state to bask in temperatures in the upper 70's to the mid 80's. Later that day, in true summer fashion, Pennsylvania saw it's first large-scale severe thunderstorm outbreak of the year. Scattered cells formed in Ohio and western PA, then formed into a powerful squall line, which swept southeastward toward Philadelphia and Washington, DC. A weak tornado was reported near New Castle, and there were reports of hail and wind damage across much of western, south-central, and southeastern PA.

Temperatures dropped a bit behind the front that helped spark the thunderstorms; highs on the 10^th were mainly in the 60's, though southwestern PA still managed the mid 70's. The next warm front swept through the state on the 11^th, bringing a decent round of showers moving west to east. Again, western PA got most of the warmth; even Erie hit 85 on the 12^th. But then the cold front moved through (with little precipitation) late on the 12^th and put a check on the warming trend for a while.

On Friday the 13^th a disturbance from the southeastern U.S. clipped south-central and southeastern PA, giving those areas just a little bit of rain. The 14^th was a mostly dry and fairly seasonable day.

Over the next few days, temperatures underwent a distinct cooling trend as an unseasonably cold pool of air from central Canada swept over the northeastern U.S. On the 15^th, a storm system gathered over the Midwest then moved east and settled over Pennsylvania. A large area of rain remained in place over our state into the morning of Monday the 16^th. Many parts of the state received over a half-inch of rain from the system; State College reported over a full inch. Cool air filtered in behind this storm, and late on the 16^th and into Tuesday the 17^th, a reinforcing cold front came through with more showers. Temperatures on the 17^th and 18^th only reached the mid to upper 40's for most of the state, and some parts of central and western PA did not make it past the upper 30's. Scattered snow showers dotted the state during these two days as PA remained underneath a cold upper-level low pressure system.

The temperature trend then did an about-face, and Pennsylvania experienced several days of steadily rising temperatures. The 19^th was a dry, clear, and cool day as the warming trend was just getting started, with high temperatures largely in the low to mid 50's. The warm front extending eastward from a storm system in the upper Midwest made its presence known over the course of Friday the 20^th, as a large area of steady rain moved west to east across Pennsylvania. After the warm front passed, high temperatures were largely in the upper 60's and low 70's on the 21^st. Another round of rain came to call late on the 21^st, as the front meandered back toward us. The front kept some clouds around on Sunday the 22^nd, but finally moved north and east for Monday the 23^rd, and Pennsylvania became a hot place to be. Several high temperature records were challenged as almost the entire state topped out in the mid 80's. Even Erie hit 82, and Philly reached 88.

But alas, a strong cold front moved in during the day on Tuesday the 24^th, and temperatures fell throughout the afternoon. High temperatures in the 70's and 80's were reached during late morning, but by the time the front had swept eastward through the state, most locations were in the 40's and 50's. A few showers and thunderstorms popped up in eastern PA in the late afternoon.

The 25^th and 26^th were beautiful clear, dry days, with just a few high clouds over eastern PA. Daily high temperatures were on their way back up: mainly in the 50's on the 25^th and the 60's the next day. During the morning of Friday the 27^th, a weak front dropped a few light rain showers onto western and central Pennsylvania, but these fizzled as they moved south and east.

The last three days of April 2001 were totally clear, bright blue days with comfortable daytime temperatures in the 60's and 70's as a huge high pressure system took hold over the eastern U.S., making for a stunning weekend.

-Evan Blaisdell

April 2001 Extremes for Pennsylvania