Overview
In the early morning of September 29th, a cold front was racing eastward toward Pennsylvania at 60 to 70 miles per hour. A line of strong thunderstorms formed in the high-shear environment that was present over the western third of the state. Severe wind gusts and damage occurred as the cold front and the thunderstorms blasted across Central Pennsylvania between 4AM and 8AM. The winds weakened, as did the thunderstorms, just after daybreak over Eastern PA.

Narrow Cold Frontal Rainbands

This case was a good example of what is termed a Narrow Cold-Frontal Rainband (NCFR, NCFRB). CTP Science Officer, Richard Grumm, has done a great deal of work studying and trying to classify these events.

These events are characterized by a strong cold front that moves rapidly from west to east, and makes damaging winds despite having limited instability, and little or no thunder associated with the winds.

The narrow, focused nature of the precipitation along the cold front itself is what gives these events their name. In the above radar reflectivity picture, note how there is little precipitation away from the wind shift itself.

While there was some thunder with this cold front passage, this one was certainly an unusual event for Central PA, as it happened in the middle to late nighttime hours (4-8AM EDT). Historically, during that time of the day, Pennsylvania receives very little severe weather.

These events happen a few times every year, mainly in the autumn, when the cold air is starting to make headways into the southern latitudes, and there is still some instability from higher moisture and daytime heating lingering from summer.

Text Reports of Damage
Summary of the preliminary storm damage reports (LSRCTP)