One of the reasons snowfall is so difficult to forecast is because small changes in the forecast have large impacts on our snowfall expectation. And if you read Matt's blog below you know one model had flurries and the other had 3-5" for us. Here's why we lose hair over snowfall forecasts...the model that showed flurries is now pumping out nearly 10" of snow for St. Louis! On the other hand, the other model has stuck to it's guns and is still near the 4" mark. But we don't just look at the numbers, we look at the dynamics of the storm.
What I'm seeing in the new model forecasts:
I noticed the storm in recent model runs has been more intense and well developed. While the timing looks to be very consistent, starting near or after Midnight, the major change is that a second wave of snow arrives Saturday night. There's still plenty of moisture and the colder air begins to move in Saturday night. This is what we keyed in on that made us raise snowfall forecasts today.
Currently we think there will be 2 to 3" on the ground tomorrow morning. Not too bad. Then we get into a lull before the 2nd wave hits Saturday evening and overnight. The snow should taper to flurries and end Sunday morning. That 2nd wave should pump our snowfall totals area wide around 4-8". The metro could very well be near or on the high end of that range, while areas South will see more rain or ice mix which reduces the snowfall totals.
What could change?
Something Kent and I talked about is if we don't see much of a lull in the afternoon, then we'd get higher snow amounts. So, one thing that could change is the expectation of lighter snow or a break in the late morning and afternoon before the 2nd wave of snow hits in the evening.
We also notice that the rain/snow/mix line is South of St. Louis, and areas like Cuba to Farmington will see some ice or rain mixed in through this event. If that line pushes a bit North it could get close to the metro and any sleet or mix would cut into our snowfall totals. It would also likely push the heavy band of snow a bit to the North.
We're in Storm Mode, which means we never stop updating the conditions and the forecast, so check back online and on-air for the very latest through this winter storm.