1PM – Update
A tornado watch is now in effect for the entire region. Thunderstorms are already prompting tornado warnings in southwest New York. Standby for live updates.
Severe Thunderstorm Forecast — Tuesday, August 22, 2017
A widespread, significant severe weather event will likely unfold this afternoon across the Finger Lakes. This will rival May 1 for the largest severe weather event of the year.
A hot, very humid air mass, strong jet stream, and impressive cold front will all combine to set the stage for some dangerous weather across the region.
Thunderstorms will likely develop by the early afternoon over southern Ontario and western New York and will organize into a line of storms.
These thunderstorms will then press east across the Finger Lakes. Isolated supercells will be possible ahead of the line, as well as embedded within the line itself.
The greatest threat will be before 5 PM for the western Finger Lakes, and between 4-8 pm for the central and eastern Finger Lakes.
Additional scattered showers and thunderstorms are possible this evening, though the severe weather threat will decrease as the sun sets.
Severe Weather Threats
Frequent lightning is very likely throughout the Finger Lakes with these thunderstorms. All lightning is deadly. If you can hear thunder, you are close enough to be in danger from lightning.
Damaging Winds- ELEVATED
Widespread damaging winds are possible today. Some of the wind could be significant with isolated pockets of structural and significant tree damage. Many reports of trees and branches down are expected. Power outages are likely in some areas.
The hail threat is currently expected to be low, with a few reports of hail around 1-1.5 inches in diameter. There is a chance the hail threat could become more significant should the atmosphere become more unstable.
There is a chance for a tornado or two today. These may occur in any cells out ahead of the main line, be could be embedded within the line itself as well. The greatest tornado threat at this time extends through the Southern Tier and into the eastern Finger Lakes and Central New York. This includes Elmira, Ithaca, and Cortland. The development of a tornado is not a certainty.
Flash Flooding- LOW-ELEVATED
Torrential rain is likely with the thunderstorms. They should move quick enough for only minor poor-drainage flooding. However, if multiple storms hit the same area, more significant flooding issues could arise.
There is one factor in the atmosphere that is not quite favorable for severe thunderstorms which could put a cap on the potential today. There is a lack of cold air in the mid-levels of the atmosphere. I have seen this disrupt severe weather events in our region before.
On the flip side, the incoming cold front is very strong and may be able to overcome that single marginal factor. If so, this will be a significant event for the Finger Lakes.
My tentative plan is to broadcast on Facebook Live later this afternoon. This feed will be posted here on FLX Weather as well. If Facebook Live does not work out, I will have another blog post this afternoon where I will have live updates.