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Snow squalls in New York and Pennsylvania

By Scott Bachmeier •

1-minute GOES-16 Red Visible (0.64 µm) images — with plots of Surface Wind barbs (white), Peak Wind gusts (cyan/yellow/red), Ceiling/visibility (green), GLM Flash Extent Density (blue to cyan) / GLM Flash Points (white dots) and Snow Squall Warnings (red polygons) — from 1400-1900 UTC on 29th January; Interstate highways are plotted in beige [click to play MP4 animation]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Red Visible (0.64 µm) images (above) showed a long, narrow convective cloud band associated with a strong cold front that was moving southward and southeastward across New York and Pennsylvania on 29th January 2025. Strong winds coupled with moderate-to-heavy snow along this cloud band prompted the issuance of numerous Snow Squall Warnings across the area. The appearance of intermittent GLM Flash Extent Density and GLM Flash Point signatures suggested that thundersnow may have occurred with some of these snow squalls. Note the slight northward displacement of the Flash Extent Density pixels compared to the Flash Points (1659 UTC image) — this is because the commonly-used Gridded GLM products (such as Flash Extent Density, Minimum Flash Area and Total Optical Energy) are not corrected for parallax, as the GLM Flash Points are.

5-minute CONUS Sector GOES-19 (Preliminary/Non-operational) Day Cloud Phase Distinction RGB images created using Geo2Grid (below) helped to highlight this cold frontal cloud band — the shades of green to yellow indicated that the cloud band was either mixed phase or fully glaciated.

GOES-19 Day Cloud Phase Distinction RGB images, from 1401-1956 UTC on 29th January [click to play animated GIF | MP4]

Categories: GLM, GOES-16, GOES-19, Lightning, Winter weather