Severe Weather over western Pennsylvania

 On Day 3 Wednesday of the Hazardous Weather Testbed, we monitored weather for the Pittsburgh CWA (PBZ), and in particular lightning and severe weather that could affect the Pittsburgh Mimosa Festival and the Allegheny Caribbean Carnival. We issued several SVRs that ended up verifying with multiple hail reports of 1.0” in diameter (quarter size) and a few damaging wind reports in northern WV. See SPC reports further below.

The main radar products that were used for severe weather decision making were the 0.5° Base Reflectivity and Base Velocity products, the MRMS @-20C, Vertically Integrated Ice, and MESH. LightningCast V2 and Stoplight V2 were also used to support DSS activities at the two festivals mentioned above. At the beginning of the event at 18Z, thunderstorms were already impacting the two festivals as seen on the Time-Series plot of LightningCast with observed GLM flash counts and near 100% lightning probability at the exact locations.

Figure 1 above shows the probability of lightning at the location of the Allegheny Caribbean Carnival from LightninCast V2 (green line) and the observed flash counts from the Geostationary Lightning Mapper (GLM) instrument. Notice that the second spike in lightning probabilities did not result in lightning activity detected at the exact location as shown by the lack of GLM flash counts. In this second spike in lightning probability, the LightningCast V2 had a small false alarm than the V1 product.

Figure 2 above shows the Pittsburgh Mimosa Festival experienced two rounds of thunderstorms, one between 18Z and 19Z and a second round between 1945Z and 20Z.

We also monitored the Stoplight V2 product to give the all clear message that the lightning threat had ceased.

Figure 3 above shows the Stoplight product indicating the cessation of lightning and when it was good to give the all clear message that activities could be resumed.

Figure 4 above shows the MRMS Isothermal Reflectivity product @-20C which often shows the most significant storms and the storms that might contain hail alongside the Vertically Integrated Ice. SVRs polygons are also shown to indicate where SVRs were issued.

Figure 5 above shows the SPC’s Severe Weather reports from Wed May 13 2026. Four hail reports of quarter size were reported in western Pennsylvania and three wind damage reports in northern WV.

-Hurricane Specialist