While the Catechism only gives two examples of serious reasons to miss Mass, specifically illness or the care of infants (sometimes translated 'young children'), these are by no means the only serious reasons one may have to miss Mass.
Travel concerns can't be brushed aside. Sometimes one may not be able to get to Sunday Mass because of distance, or a problem with transportation, and these sorts of things are usually out of our hands. When weather conditions exist that make it unsafe to drive, in that you may not arrive safely, may cause problems for emergency crews, etc., it is my opinion that this would indeed constitute a serious reason that would permit one to miss Mass.
Remember, the Catechism puts it this way:
2181 The Sunday Eucharist is the foundation and confirmation of all Christian practice. For this reason the faithful are obliged to participate in the Eucharist on days of obligation, unless excused for a serious reason (for example, illness, the care of infants) or dispensed by their own pastor.119 Those who deliberately fail in this obligation commit a grave sin.It's my understanding that ordinarily one's pastor will only dispense one if there is a reason you know about in advance, or a continuing situation of some kind (e.g., business travel to Saudi Arabia). Inclement weather usually has to be assessed at the time it happens, as does illness or the needs of an infant.
Here in Texas we don't get icy/snowy weather very often; the downside of that is that we also don't have a lot of road-clearing equipment. So it's been my family's practice to go to the Texas Department of Transportation website and check out road conditions. When they issue advisories that strongly state that only emergency travel should be undertaken, and that for anything less than an emergency you should stay at home, we take that seriously--and yes, that has led to one Sunday where we remained indoors and missed Mass. That particular storm came in Saturday afternoon, so the chance to go to an anticipation Mass was not there, and the icy roads weren't any better until late Monday or early Tuesday from what I remember.
The point is that we don't, as a family, take missing Mass lightly. We wanted to go to Mass that Sunday, and hoped that the weather would clear up in time for a noon or even a 5 p.m. Mass. But it didn't, and we saw lots of examples on the news of people who went out and drove anyway and had to be pulled out of ditches, so we knew our reasons for not attending were good ones.
Many people today don't live within walking distance of a Catholic parish. Many of us have to rely on car transportation, which means paying attention to driving conditions. If we make the prudent decision to stay home and find out later that the roads weren't as bad as the Transportation Department was telling us, there would still be no sin, provided we had done our best to ascertain the truth of the situation. This is because, as the Catechism puts it, we have to "deliberately fail in this obligation" to be guilty of sin; trying to figure out if you can make it to church safely and concluding, reluctantly, that you can't, isn't a deliberate failure of the obligation to attend Mass, but an attempt to consider honestly a serious reason that may be an impediment to the obligation.
Clearly, each family and each storm will be different. If there's a thin and melting layer of snow on the road and you have a four-wheel drive vehicle equipped with snow tires etc., there's probably not really a valid reason to stay at home. But as the Northeast and Midwest continue to be blanketed by heavy snow, and as Chicago officials tell people point blank to stay off the roads unless travel is absolutely necessary, many Catholics may have to pay close attention to the weather this weekend and make good choices about whether the inclemency constitutes a serious reason to stay at home and miss Mass.