The good news is that the high heat and humidity is about to end. However, this airmass will not move out without causing a host of other troubles as it departs.
A strong cold front will move across the Finger Lakes and surrounding regions Thursday afternoon and Thursday night. Out ahead of this front, copious amounts of moisture that will challenge daily record levels (using historic Precipitable Water data from the upper-air observation station in Buffalo) will bring the threat for active weather.
As the front (blue line) and a pre-frontal boundary (dashed yellow line) move east, showers and thunderstorms will increase in coverage and intensity across our region. Torrential downpours will be the primary concern, with flash flooding possible at any time until the front moves through tonight.
Flooding is not the only threat though. Conditions are just marginal enough to raise some concern about localized severe weather. The threat is very subtle, and everything would have to come together perfectly for it to be realized. But there is at least a chance for a few thunderstorms to become strong to severe, with damaging winds the primary threat. However, a brief tornado cannot be ruled out either, especially near Lake Ontario and across Central New York.
The front will take its time crossing the region, but by midnight, most of the activity should be to the east. Widespread rainfall amounts over 0.5″ are almost certain, and many areas could see 1-2″. Locally, even higher amounts can be reasonable expected for any areas that see particularly heavy and slow moving storms.
Stay tuned to your favorite weather media outlets throughout the day.