Fall is a time of year when the weather becomes decidedly more active around the Twin Tiers, and while parts of the area did see their first slushy accumulation of snow yesterday morning we have yet to see what many meteorologists would consider to be a "strong" cold front pass through the area. The latest computer model guidance, however, continues to strongly suggest that such will not be the case by the end of this upcoming weekend.
There are a couple of issues to consider regarding the weekend storm. Be advised, however, that the thoughts/opinions expressed in this blog entry are my own personal forecast ideas and may not necessarily be representative of what my fellow colleagues are thinking! But here are the potential "threats" I see with this upcoming event:
1) Heavy Rain. Although this will be a fast-moving storm with the bulk of the precipitation falling in a period of six hours or less, it will have plenty of "juice" to work with as it taps into moisture originating from the tropics. One parameter meteorologists look at to determine heavy rain potential (and this is by no means the only parameter) is a measurement we call precipitable water, and the precipitable water with this system is forecast to climb into the 1.0-1.5" range. Considering we are now approaching the month of November, that is pretty respectable for this time of year! Heavy downpours will certainly be a possibility with this, particularly Saturday afternoon into Saturday evening.
2) High Winds with the Cold Front. Although this may or may not materialize, I think this could potentially be the biggest issue with this weekend's storm. One of the computer models we look at, the GFS, is forecasting wind speeds to reach 65 knots (close to hurricane strength) only 4000 feet above the surface, and 80 knots or more than 90 mph up around 6000 feet by late Saturday afternoon, compliments of what we call a strong "low level jet." These winds are expected to remain safely above the surface for the most part (although it will certainly get quite windy on the hilltops and in southeast-northwest oriented valleys)....but there is some possibility that a narrow line of heavy rain showers, either with or without lightning, may accompany the cold front as it plows across the area Saturday evening. If this were to occur, then we could see some of those very strong wind speeds "mix down" to the surface and produce localized wind damage. We refer to this type of situation as a "low-topped convective wind event" and on occasion these setups can be quite severe. It's definitely something to keep an eye on.
3) Strong Winds Behind the Cold Front. Whether or not we do in fact experience a low-topped convective wind event...it is almost a certainty that we will see strong winds immediately behind the passing cold front. As cooler air rushes into the area and the atmospheric pressure rises very rapidly, there will be a several hour window during which strong winds from aloft will be easily transported down to the surface. Although the ferocious low level jet that I referred to in the above paragraph will have passed by to our east, winds could still gust into the 40-55 mph range which is still enough to knock down tree limbs and resultant power lines. This is more likely to occur than the convectively-generated winds I referred to above, but obviously it isn't quite as threatening.
It's an interesting forecast, and you can bet we'll be watching it here over the next few days. Be sure to stay tuned to WBNG-TV for updates, and of course you can always read our discussions on the website as well.