During the afternoon hours of 18 January 1999, a strong cold front moved from west to east across Pennsylvania. Along this cold front a band of rain showers and thunderstorms developed. The front and the showers moved eastward across central Pennsylvania from about noon through 4 PM. A summary of the reports severe weather and flooding was issued Monday evening. High winds and hail dominated southwestern Pennsylvania and flooding problems plagued eastern Pennsylvania. The potential tornadoes are still under investigation.

All available radar imagery can be viewed by clicking here.

The approaching NCFR was about to enter the State College Forecast Offices County warning area around 1735 UTC as seen on the base reflectivity product. The velocity data at this time showed strong southerly winds over central Pennsylvania (green inbounds to south and red outbounds to north) and westerly winds behind the NCFR to the west of the radar. It is interesting to note the 60KT plus winds a few thousand feet above the surface across southern Pennsylvania.

By 1747 UTC (1247 local) the southern end of the line had entered Somerset County. The line looked more impressive over Indiana County, west of the KCCX radar. The base velocity data showed the strong low-level westerly winds along and behind the line.

By 1758 UTC, the line was entering Clearfield and Cambria Counties. The southern end of the line was over eastern Somerset County, and entered Bedford County shortly before 1810 UTC (1300 Local). The strongest and most defined cells were over Clearfield County. Both the velocity and storm relative velocity (SRM) data showed the strong westerly winds behind the line and the convergence along the line. The SRM cross section, taken along the white line the in the SRM plan view map, showed the low-level convergence along 4-5 miles from the origin of the line. The damage in near Burnside in Clearfield County most likely occurred between 1758 and 1810 UTC (1 PM) not the 125 PM time reported in the LSR.

The reflectivity image at 1821 UTC showed the line continuing to move eastward. A cross section taken through the line showed the west to east tilt of the cell along the line. The base velocity data at this time clearly showed the low-level westerlies to the west of the radar and the strong southerly flow at and to the east of the radar. There was an interesting little velocity feature and some enhance reflectivity data just south of I-80 (the long gray curve) in Clearfield County. Despite this, no reports of severe weather were reported between DuBois and Clearfield. The hardest hit area would have been Pine Township, northwest of Mt. Zion.

By 1902 UTC, the line had passed east of State College and strengthened. By this time both an NCFR and a wide cold frontal rainband (WCFR) were clear observed by the radar. The enhanced echoes in the WCFR, to the west of the radar were probably due rain and snow producing bright banding. Some areas did receive several inches of snow as the WCFR moved through. Many areas received a mixture of light rain and snow as the WCFR move through. The reflectivity cross section through the NCFR showed the east to west tilt and the elevated 45-50 dBZ returns from 2-4 KFT in the line. The 1913 UTC image shows the NCFR and the WCFR along with a cross section across both lines. Note how "narrow" but intense the leading band is compared to the weaker and wider trailing band. East is to the left in this image (sorry!).

By 1942 UTC the line began to weaken. The leading edge of the WCFR can be seen at the left edge of the image, about to move over the radar site. The NCFR continued to weaken and the WCFR fractured into three areas by 1948 UTC.

The radar did not estimate a lot of rainfall along the NCFR. Most of the radar estimated rainfall was confined to the eastern portions of the State as seen in the 2139 UTC radar estimated rainfall. The same chart in mm is also available. Maximum estimated rainfall was on the order of 0.5 inches (12.5 mm). A comparison to observed data should reveal how good these numbers are, typically, the radar grossly underestimates rainfall amounts with NCFR events.

A storm survey was conducted on 19 January 1999 by Tom Dunham (WCM) and Dave Ondrejik (SH) of the potential tornadoes in Cambria and Bedford Counties. The survey determined that the most likely cause of the damage in Cambria County was from straight-line winds. A small, F0. tornado damage swath was found in Bedford County. This tornado formed along the leading edge of the line and was probably a short-lived gustnado.

The damage in Cambria County was from straight-line winds, which ripped shingles off a home and took the roof off of a mobile home. A temporary roof was in place by 19 January. The winds did significant damage to a mobile home in the affected area, mainly ripping the tin roof off the structure and blowing the insulation across the country-side and into trees.

The damage was more severe in Bedford County where an F0 tornado moved through a narrow area, topping trees and leaving striations in the snow. Several homes and an oil change business were affected by the tornado.

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The National Weather Service office in State College issued a flood potential statement (ESF) on Friday, 15 January. This product spoke of the potential of locally heavy rains and snowmelt, which could contribute, to flooding by Monday. Special weather statements (SPS) were issued on Sunday morning at 4 AM and again at 1130 AM. These statements emphasized the potential for strong gusty winds with a line of showers and thunderstorms and some flash flooding. The statement was re-issued at 1000 PM Sunday and 0400 AM Monday. The situational awareness of the potential problems that would most likely arise were quite high.

The first severe thunderstorm warning was issued around 130 PM Monday afternoon. A total of four warnings were issued as the line of thunderstorms moved eastward.

The first Flash Flood watch was issued on Sunday afternoon around 4 PM. This statement emphasized the potential for locally heavy rains and snowmelt contributing to flood potential in central Pennsylvania. Many of the rivers and streams were still frozen, this lead to the concern in the statement of the impacts of river ice moving and causing ice jams. A similar situation had developed on 19 January 1996 leading to some serious flooding from 19-21 January 1996. A Flood warning was issued for Swatara creek on Monday morning primarily due to the impacts of snow and ice melting.

To browse products issued by the NWS in State College and Mt. Holly click here.