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Icing Help


The Current Icing Product (CIP) combines sensor and Numerical Weather Prediction model output to provide an hourly, three-dimensional diagnosis of the icing environment. The Forecast Icing Product (FIP) is similar to CIP except that it does not include the sensor inputs. CIP/FIP outputs include calibrated icing probability, icing severity, and potential for SLD (supercooled large drop - includes freezing drizzle and freezing rain). Probabilities do not reach 100% because the data available to diagnose icing do not allow for a diagnosis with absolute certainty at any given location in space. Icing severity encompasses five categories (none, trace, light, moderate, and heavy). SLD potential appears as a red hatching.

CIP/FIP are output on a grid with pixels every 20 km in the horizontal and 1000 feet in the vertical. FIP Forecasts extend hourly to 12 h. ADDS displays every other level except on the Flight Path Tool that provides access to all levels. Besides the individual levels, you can select a composite, maximum value of all altitudes, labeled "max." This image provides a quick overview of the regional icing threat.

On the icing probability graphics (sample shown in Fig.1), the scale is from 0 to 85%, using cool to warm colors with warmer colors indicating higher icing likelihood. On icing severity graphics (sample shown in Fig. 2), the scale is from trace (very light blue) to heavy (dark blue). SLD icing threat is indicated by overlaid red hatching (sample shown in Fig. 3). Icing severity can also be "masked" to show points where the icing probability is greater than 25% or 50%. Either of these options use a gray color to mask the severity pixels where icing probability is less than the threshold value (sample shown in Fig. 4) but still exists.

Icing Probability
Figure 1: Icing Probability
Icing Severity
Figure 2: Icing Severity
Icing Severity with SLD overlay
Figure 3: Icing Severity with
SLD Overlay
Masked Icing Severity
Figure 4: Masked Icing Severity

Pilot reports (PIREPs) of icing are overlaid on the single-level graphics (legend found at the bottom of each graphic) if within 1000 ft vertically and 90 min temporally. On the composite graphic, PIREPs for all altitudes are shown (except negative icing reports, which are omitted for the sake of clarity).

Those interested in learning more details of the science used to create CIP are invited to read the following paper which is available free-of-charge to the public at

Bernstein, B.C., F. McDonough, M.K. Politovich, B.G. Brown, T.P. Ratvasky, D.R. Miller, C.A. Wolff and G. Cunning, 2005: Current Icing Potential (CIP): Algorithm description and comparison with aircraft observations. J. Appl. Meteor., 44, 969-986.

Freezing Level Graphic

The freezing level graphic shows the elevation in 100s of feet of the lowest freezing level. Areas colored white are where the surface temperatures are below freezing. The freezing level graphic comes from the RAP model and is produced hourly. The plots run from the analysis with forecasts running every 3 hours out to 18 hours.

Freezing Level
Figure 5: Sample freezing level graphic