CAWS collaboration for icing over SE Wisconsin

This morning one of the areas of icing interest at the CAWS desk was the Great Lakes, particularly through southern Wisconsin and the central portion of Michigan's lower peninsula. FIP/CIP and RAP signals were fairly broad across the area at 1600 UTC in lower levels. The GOES-R flight icing threat (FIT) index along with other tools was able to help narrow that area down.

The FIT consistently indicated areas of heavy icing throughout the morning hours in Wisconsin and Michigan. Because of the marginal signals from the models earlier in the morning, the forecaster at the CAWS desk hadn't yet looked at issuing a statement for that area until it was pointed out in the FIT. At 1615 UTC, a moderate to severe PIREP from a helicopter was noted in SE Wisconsin in the high index values shown in the FIT.

20160222 1615 UTC Flight Icing Threat Index overlaid with PIREPS and the CAWS issued at 1738 UTC. Note high index values (pinks and reds) suggesting MOG to heavy over eastern Wisconsin

Above is the 1645 UTC FIT image. As mentioned, the FIP/CIP and RAP kept the areas pretty broad in this case. The forecaster was then able to use the FIT to further narrow down an area of enhanced icing risk (inner blue dashed circle above) and issued the CAWS above at 1739 UTC. The area was extended into the central lower peninsula of Michigan as a loop of the FIT imagery indicated movement in that direction throughout the daytime hours. Also included was a broader area of lower risk covering much of Wisconsin and lower Michigan.

Icing cloud layer bases/tops were also examined in this case:

20160222 1445 UTC Icing cloud base heights overlaid with PIREPS and the issued icing CAWS

The above image shows icing cloud bases this morning over the area of interest. The icing PIREP issued at 1645 UTC indicated moderate to severe rime at roughly FL030. Icing base heights at the same time indicated bases between FL030 and FL040, which verified very well.