The difference between snow and drizzle
It’s been a struggle to ‘keep ice in the clouds’ since last night. With that struggle comes the difference between snow and drizzle. We’ve been fighting that barrier between the two as it’s floated north and south across the state line in the last 24 hours.
For snow to form, we need at least some part of the cloud to be in the range of -10 to -20°C. If we don’t, we end up with drizzle. That’s been the case south of I90 since last night. We’ve seen that threshold come and go.
You can see in the vertical profile of the atmosphere over north Iowa. Where the red and green line are close together, we have clouds. Those lines diverge in that -10 to -20° range defined by the pink. Further north, we’ve had more ice in the clouds more steadily and that’s resulted in higher snowfall amounts in the last 24 hours.
Clouds should cool enough tonight to kick the drizzle out and leave us all with snow showers.