It has been something that we have been watching for the past couple of days, but as we get closer, we feel it is something worth mentioning. Some of you weather enthusiasts have been reading local National Weather Service office forecast discussions, and have asked us our opinion.
The National Weather Service in Des Moines this afternoon stated the following in their forecast discussion:
Warm front to lift northward through the area, with a dry-line moving into the state during the afternoon hours Sunday. NAM/GFS both painting MUCAPE across the area so scattered thunderstorms still expected. Shear parameters very strong, and if can get enough instability, a severe storm will be possible, especially close to the dry-line/frontal boundary as it moves into western/southwestern Iowa that afternoon. Shear parameters suggesting possibility of a weak, brief tornado in any stronger storm that could get going. We will be on the north/eastern fringe but is a more typical scenario for a very late season severe threat for the area.
So what does this mean? While the potential for a weak tornado may be possible across southwest Iowa due to the strong shear, or what we call a high shear/low CAPE day, it is a very low threat. The bigger threat with any storm that does become severe, will be marginal damaging wind gusts.
Severe weather in late December is more difficult to come by, mainly due to the temperatures, and lack of moisture. What is even more rare, is Christmas day tornadoes. Tornadoes on Christmas day are more common over the southeast states of Louisiana, Mississippi, Alabama, Georgia, and Florida.
We will keep an eye on this threat, especially since it is Christmas day, but it is nothing to stress out over.