Enroute Icing

### Produced by The COMET® Program

### Step 1: Diagnosing Locations of Icing » NWP Analyses » Current Icing Potential (CIP) - Data

The CIP data plots below show only the maximum value for each product between FL010 through FL300, but we can use other model and observation data to fill in the FLs for icing and severity. In practice, however, we’d have 00-hour data for all FLs at 2000 foot intervals, which we could directly check for consistency with other model data and observations.

The first product, the maximum probability for icing, also plots icing reports by type and severity near report time for CIP validation. We see that by 13 UTC, the high maximum probability area contains numerous reports of light to moderate icing.

The second product, the icing severity composite, shows the highest icing severity as indicated by the color bar shading. Here, the validating icing reports show severity using digit size and value.

Finally, the maximum SLD potential product shows the locations of the highest diagnosed risk of SLDs in percent, using the RUC analysis. PIREP icing type and severity are indicated by the letter font size in accordance with the legend beneath the map.

Because SLD pose a significant threat for moderate or greater clear or mixed icing, CWSUs emphasize their presence in the analyses. Forecasters issuing Meteorological Information Statements (MISs) with icing and other significant weather outlooks for the next 12 to 18 hours will warn of significant icing risk if SLD are forecast, even with low icing probabilities. In our case, we have a high probability of SLD in northeast Kansas and northwest Missouri, not far upwind of the Chicago CWSU service area.

NOTE: If you have used the NWP analysis as part of diagnosing icing and found that it agrees with the observations, you don’t need to validate the analysis again. You can go directly to using the NWP forecast.