Rain or Snow: The Fine Line of a Complex Forecast

gfs_slp_048mThe track, temperature and overall behavior of an impending storm system could mean the difference between a cold, soaking rain and several inches of snow.  That’s the problems forecasters are dealing with yet another storm system set to enter Iowa at a terrible time.

A low pressure system is expected to swing through Iowa from the southwest on Wednesday, the day before Thanksgiving and one of the busiest travel days of the year.  This storm system will bring a fair amount of moisture with it, but the bigger question is what type of air mass will exist over Iowa when that moisture arrives.

As you can see in the weather graphic to the left, the red lines indicate areas where the air mass is expected to remain above freezing.  Blue lines, of course, indicate an air mass more conducive for snow.  At this time it appears most of eastern Iowa will avoid the snow, but areas of northern and western Iowa could see some accumulation.

Sound simple enough?  Well it’s not.  There is a lot of time before this storm system arrives on Wednesday and a lot that can change.  The cutoff between rain and snow can change dramatically over the next few days and we also need to monitor the amount of moisture that comes in with this system.  If areas seeing snow also see .20” to .50” of rain, that could translate into snow totals above 6 inches in parts of the state.

This is a big concern with the expected number of people traveling on Wednesday and Thursday.  If you are one of the many with Thanksgiving plans the best advice is to stay up to date with the latest forecasts and make plans to adjust your travel times if needed later.  We’ll continue to monitor the latest trends and bring you more updates in the days to come.

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