Patterns of ice accumulation and forest disturbance during two ice storms in southwestern Virginia

Major ice storms deposit heavy loads of freezing rain on trees, causing catastrophic forest disturbance in eastern North America. During 1994, two ice storms struck southwestern Virginia within a three-week period. Heavy ice deposition occurred during each storm when warm, moist air was advected over a shallow subfreezing layer at the surface. Cold-air damming helped trap the cold surface air, as is typical for ice storms in parts of the Appalachians and Piedmont. Heaviest forest damage occurred on mountain slopes facing south and east. Ice damage in these topographic positions removed approximately 30% to 60% of total basal area and created large canopy openings. Several processes may have contributed to topographic variations in ice accretion, including orographic effects on rainfall and influences of wind on twig surface and raindrop thermodynamics.