Confidence is increasing for a winter storm to impact the area next week. Models have been oddly very consistent on timing, path, and strength of this system, which is currently lurking in the central Pacific as of the time of this post. The two primary models that we are looking at, the European ECMWF and American GFS, both have precipitation beginning Monday night across southern Iowa and overspreading the state by Tuesday morning. It’s important to note that there is a lot of issues with this before a more refined forecast can be made.

The first and foremost one to note is that, again, this storm is over the Pacific right now. Computer weather models are not receiving and will not receive any form of upper air observations into the system until it reaches the west coast. The system is over what could be called a “data poor” environment over the ocean where we have only a few buoys and some ships to provide this crucial data to us. This valuable data that could influence changes in models in the coming days and is something to pay attention to. The event is still several days out and, while models have been very consistent, things can change very quickly. The forecast presented is subject to change as we get new data into the models over the next few days.

Personally, I’m suspecting we may get some inconsistency pushed into the models as we get this new data. This is the reason we are holding back on releasing snowfall totals at this time unlike many media outlets in the state. It is literally a roll of the dice at this point in time and the numbers are pure guesses with the data available. Forecasts created at this point are not created on pure skill whatsoever. Sure, I could tell you what the models have.. but what good would it be, when it will likely change? Not to mention, it’s standard policy and ethics for us to not release forecast totals more than three or four days.. at the earliest… in advance. The numbers you are currently seeing from media outlets are essentially computer model guesses and are nearly guaranteed to change.

Back to weather anyway, the second issue that we will face will be the thermal profiles across the state at the time of this event. The freezing line will be dangling in the southeastern part of the state which, as this jumps around, will influence the forecast greatly. This could mean the difference between heavier snow accumulations in the southeast, or a mixture, or a pure rain solution during the day Tuesday.

There will be a lot of moisture available for this system to tap into with some instability as well (wait, isn’t that a severe weather term?). Well, some instability can create lightning and thunder, so we may see some convectively-influenced snow bands (and thundersnow, better call Jim!) which will bump snowfall totals even farther up than currently expected. With the ample amount of moisture available, significant accumulations are possible, and convectively-banded precipitation would only support this cause even more. But it’s really hard to say with a hardcore certainty on where this will setup. Winds is also one of the bigger concerns with this event. Winds in the 35-45 MPH range will create severe travel difficulties during this period. With it likely ending up being a dry snow, things will easily blow and drift around.

We will likely be releasing our first full forecast package with totals included either tomorrow or Saturday. Please keep it tuned to the Iowa Weather Network for the latest details.