Friday will be nice across the Finger Lakes, but the chance for severe thunderstorms remains for Saturday.
High pressure building into the region will bring sunny, less windy weather for the end of the work-week. Clear skies across the Finger Lakes should persist through the day and into the first half of the overnight hours.
Temperatures will be a bit warmer today, with highs mostly in the mid and upper 60s and a few places touching 70 degrees. Winds will be lighter, but still occasionally gusty. Speeds will be 5-10 mph from the northwest, but gusts could reach the 20-25 mph range, especially this afternoon.
The forecast for Saturday remains highly uncertain, as severe weather evolutions often are. At this point, however, confidence is growing in at least some isolated intense thunderstorms later Saturday.
The morning will start off with the remnants of Friday evening’s storms diving southeast into the area. Western areas of the region stand the best chance at morning rain and some rumbles of thunder. Severe weather is unlikely during this morning precipitation. How far east this rain gets, and how long it lingers before pushing to the southeast, are uncertainties in the forecast. However, they are not the main factor for severe weather.
Even in the somewhat likely case that clouds will remain fairly thick across the region during the middle of the day, warm and humid air will be pushed into the region on southwest winds. Any sunshine that does develop will only add to the instability, but there should be enough for strong to severe thunderstorms regardless of the sunshine.
The main question I have in my mind is how widespread will the thunderstorms be Saturday afternoon and evening? The primary forcing agent- a cold front- will not move into the Finger Lakes until early Sunday morning. With the front far to the northwest during Saturday, other factors will be necessary to develop thunderstorms.
I do think some of these factors will be present, including wind boundaries left behind by the morning rain, upper atmosphere support and other wind shifts. With these more subtle boundaries, it is difficult to tell the degree to which they will trigger storms. However, it seems probably that at least isolated thunderstorms should develop as early as the mid afternoon Saturday and possibly continuing well after sunset.
Strong wind profiles should be able to organize these storms into severe structures, whether that be supercells and/or small line segments. Large hail, damaging winds and even a couple of tornadoes will all be possible. How widespread these hazards become is the question.
On my map, you will notice I have a ‘FLX Severe Weather Scale’. This scale takes into account both the intensity and coverage of thunderstorms, relative to our specific climate. The threat level for Saturday is currently labeled as ‘Elevated’, which is the third level of severity. Should the threat tomorrow look more isolated, the overall threat could drop to ‘Low’, given that the majority of the region would not see severe weather. An upgrade to ‘Outbreak’ seems unlikely, as outbreak events typically impact the majority of the region through widespread supercells or a squall line.
Given the uncertainties in the evolution of tomorrow, it is imperative that this forecast receives a proper response. Vigilance is needed tomorrow, especially for those with outdoor plans in the mid to late afternoon and evening. However, I cannot stress enough that uncertainties remain and the overall threat could be decreased. Please check back for updates tomorrow morning, and possibly this evening.
Spread a cautionary word to your friends and neighbors. Something along the lines of ‘Some bad storms are possible tomorrow, but they don’t really know yet. Keep an eye out.” is appropriate. “We are going to have a tornado tomorrow!” is not. Please help my mission of informing, but not hyping, with real weather information.