Sometimes the best way to predict the future is to look at the past. Many people don't know that there was a precedent to this early season snow storm -- and it was much earlier, when almost all the leaves remained on the trees. Below is a reprint from NCDC detailing the storm, and below that, a comparison with what might happen tomorrow.

It's certainly fair to say that a storm of this magnitude hasn't happened "in recent memory" or "in the Internet era" in the Northeast -- at least as far as I could tell. So 1987 is the most recent comparison. WBNG says that it was the record earliest snowfall in the Northeast, and twenty people were killed by the storm. The New York Times also describes the chaos as trees fell and power went out.

Location: This storm, as far as I can tell from NWS reports and the sources listed above, was limited to New England -- it did not extend southwest through Pennsylvania, Maryland, and the Virginias as our maps predict this one will.

A comparison of the surface map during the heaviest snowfall during the 1987 storm versus the official NOAA prediction for the same Saturday shows that the storm is expected to be further offshore this time around, which could mean lesser amounts of precip, or could only mean more cold air will be allowed in to combine with the moisture.

Snow Ratio and Amount: AccuWeather.com meteorologist Mark Mancuso stated in our morning meeting that snow ratios (a measure of the density of snow) could be as low as 5:1. The 1987 storm featured ratios as low as 3.5:1; applying a reasonable error factor, it sounds like the weight of the snow could be similar (lower ratios = heavier snow). Snow ratio sometimes fools meteorologists and models into thinking there will be less snow than actually happens in these situations. Up to 22 inches was measured from the 1987 storm and some models are hinting that much could fall Saturday. Thundersnow was also reported according to WBNG, which is something that meteorologist Henry Margusity warned about for Saturday.

Wind: This could be a significant factor. It's hard to get a handle on how the wind was with the 1987 storm, but Henry is predicting 40-mph winds in New England with this event. That will aid in downing trees.

Time of Year: The 1987 storm, incredibly, occurred three weeks earlier than this one, when most of the Northeast still had leaves on the trees. Now that we're at the end of October, many higher-elevation areas lack leaves (as discussed yesterday). This would seem to say that damage from Saturday's storm will be less than 1987, although I suspect that correcting for population increases and urban sprawl probably negates most of that. Certainly when you add in the additional areas of Pennsylvania and the Appalachians that will be affected, it wouldn't surprise me to see more people lose power this time around.

The Irene Factor: I'm still unsure of how the previous tree damage from Hurricane Irene will factor into this weekend's storm, but I mentioned yesterday that it's occurring in the same area. On the one hand, she would have taken out the weak and damaged trees, which should lead to less tree damage this time around. On the other hand, she may have weakened or damaged additional trees which are now teetering. The 1987 Hurricane Season had no similar storms.

Traffic Problems: As far as traffic accidents, I'm worried that this first storm (as it was in 1987) will cause icier roads because there is no treatment on them (I always say: It's the first storm that gets you). The number of roads closed will depend on the number of trees downed, and the preparedness of the local and state municipalities.

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