A Word on Forecast Confidence
Once in a while, the weather can really throw meteorologists for a loop. Complex weather patterns and razor thin margins of error can wreak havoc on the forecast. Sometimes, the best a meteorologist can do is say that they just don’t know.
The rise of stating confidence in a forecast — a practice I have been doing regularly since 2010 — is a great thing. However, it is not really that helpful for a meteorologist to just say the forecast is complex and that confidence is low.
It needs to be taken a step further and the different outcomes need to be spelled out. That way, at least there is an idea of what is possible and the public can prepare.
The weather this weekend is one of those set ups. A frontal boundary will be very close to the Finger Lakes. A series of thunderstorm complexes and an area of low pressure will ride along this boundary.
The big question is how far north will the precipitation come? Given that it is the weekend, and a busy one at that with Grassroots ongoing in Trumansburg, the difference between a steady rain and sunny day is huge.
So, for both Saturday and Sunday, I am presenting an overview of the setup and two possible scenarios. Both will be possible on both days, but I will specify which scenario gets the slight edge.
With a little luck, these won’t be too far off the mark!
There are two periods of uncertainty on Saturday.
First, a complex of thunderstorms will be moving southeast out of the Great Lakes during the morning hours. The uncertainty with this is whether or not the Finger Lakes sees light rain showers to the north of the primary complex.
Secondly, additional steady rain and thunderstorms are likely Saturday evening across northern Pennsylvania. Again, the uncertainty is how far north these will spread.
Scenario 1- (60% Likely)
I am fairly certain that the morning thunderstorm complex will keep its heavy rain and potentially strong thunderstorms well south of the Finger Lakes.
However, I do expect at least some scattered showers to move through the region, especially between 8am-2 pm. Some steady light rain may be possible at times.
Temperatures would remain in the mid to perhaps upper 70s through much of the day after initially rising from the 60s early on.
The rain will gradually drift south towards the NY/PA State Line, where it will intensify late in the afternoon through the evening hours. Southern Tier counties may get into some of this heavier rain with just some showers across the southern Finger Lakes.
The northern Finger Lakes would dry out by the late afternoon and remain rain-free during the evening.
Scenario 2- (40% Likely)
This scenario is probably the one most people will hope for, and it definitely could happen. I only favor it slightly less than Scenario 1, purely off of gut feeling. This scenario also has the support of the European model, which I typically follow closely.
For this scenario, the rain showers on the northern edge of the morning thunderstorm complex dry up long before they reach the Finger Lakes.
Instead of showers, much of Saturday would have a mix of clouds and some breaks of sun. A stray shower could be possible, but generally dry weather would be expected until later in the afternoon.
The late afternoon and evening could remain dry as well, with most of the rain at this point near or south of the NY/PA State Line.
Temperatures would be warmer in this scenario, with highs in the low to mid 80s.
On Sunday, the frontal boundary over Pennsylvania will start to lift north as low pressure rides along it from the west.
As this low-pressure system approaches, showers and thunderstorms will likely break out. With a very moist atmosphere and strong winds aloft, both severe thunderstorms and flash flooding are possible.
Scenario 1- (70% Likely)
The weather models have been consistently showing showers and thunderstorms for Sunday across our region since last weekend. I will continue to ride with that and say that I do expect rain in the Finger Lakes on Sunday.
However, the picture is a bit more complex than that.
There was a very sharp cut off between an environment conducive for severe weather and a more stable environment on Thursday across the region. Such a set up will be possible again.
I do think a few strong thunderstorms will make their way into our region. The areas most at risk will be the Southern Tier and southern Finger Lakes. Flash flooding will also be a risk in those areas.
Further north, I do expect rain, but the severe threat may be fairly limited. Still, some flooding issues could arise.
Scenario 2- (30% Likely)
In this scenario, showers and thunderstorms become widespread across the Finger Lakes. With plenty of moisture and instability, severe weather and flash flooding is common place.
The greatest threat in this scenario would be the flash flooding. Numerous thunderstorms tracking over the same areas could easily put down a few inches of rain. That would be more than enough for flooding.
Damaging winds would be the next threat, followed by hail. A tornado would also remain possible, especially given that a similar pattern produced tornadoes yesterday in western New York.
Thunderstorms would be most likely from the midday hours into the evening.
There is a third scenario on Sunday, but I really do not think it is overly likely. This third scenario would keep the vast majority of the precipitation to the south, with a generally quiet day across the Finger Lakes. Nice, but unlikely at this point.