Sperry-Piltz Ice Accumulation Index

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National Weather Service

Pleasant Hill Missouri



The Sperry-Piltz Ice Accumulation Index (SPIA) categorizes damage potential through the use of: (1) researched weather parameters and utility impacts and (2) the combination of forecast parameters including radial ice accumulation, wind and temperatures. The SPIA Index is an Experimental Product with coordination with National Weather Service Offices in Missouri, Oklahoma, Arkansas, Texas and Tennessee. As an experimental product, there may be times when it is not available. Additional information on the SPIA Index can be found in the Presentations and Paper sections of this webpage. If you have questions, comments or feedback on this test product, please contact the National Weather Service at the contact infomation listed at the bottom of the page.



Utility Damage and Impact Description


Some local utility interruptions possible...typically lasting a few hours.


Scattered utility interruptions possible...typically lasting less than 12 hours.


Numerous utility interruptions possible...lasting up to 5 days. Damage to some main feeder lines possible.


Prolonged and widespread utility interruptions. Damage to many main feeder lines possible. Utility outages lasting up to 10 days possible.


Catastrophic damage to exposed utility systems possible. Outages lasting several weeks possible in some areas.



Ice Accumulation

Maximum Wind Speed (mph)

SPIA Index

Day 1

Day 2

Day 3

Day 4

Day 5

Day 6

Day 7

Total Ice Accumulation Forecast



Forecast Info

Forecast Discussion

Hazardous Weather Outlook


Utility Ice Index Informational Presentation Sidney K. Sperry


Utility Ice Index Paper Gary D. McManus, S.F. Piltz, S. Sperry, R.A. McPherson, A.D. Gartside, D. McClain, T.Meyer, C.Fetsch and M.A. Shafer



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