The changes are to make today better (less rain chance) and to make tomorrow worse (greater rain chances). The changes are not due to the models, which have been struggling mightily with this set-up, but are due to observations.
Observation 1: Atmospheric flow is from the NW (meaning showers/storms that could impact our area need to be located in Michigan, not Illinois/Indiana.)
Observation 2: Lots of shower activity present in Michigan this morning. This means there is lift and instability in the atmosphere over Michigan, and that should flow to the SE over our area late tonight and tomorrow.
Observations always beat models. But we can only observe current conditions, not conditions that will be happening 48 hours down the road ... this is how models can help as a tool, but why one must recognize their weaknesses and evaluate "does it make sense?"
Now we have to wonder about Monday ... is there another round of showers coming our way?
- Maybe ... if Sunday's energy is weak and disorganized it will have little to no impact on the upper air flow meaning Monday's energy flows toward us.
- Maybe not ... if Sunday's energy is organized, it will alter the flow and cause Monday's energy to track south.
I think it will track south. Again, based on observations, the energy for Sunday seems organized, leading to widespread showers and a storm for tomorrow, but also meaning the showers and storms for Monday will be shunted to our south.
Again, it could change ... but any changes will be made based on observations ... not models.
Anyway, enjoy the weather.