Monday Severe Threats
The primary focus in the weather continues to be a complicated set-up today that may yield some severe thunderstorms across the region.
1 PM – A weather watch is likely to be issued across our region in the next 1-2 hours.
Overall, the weather setup is greater for severe weather today than it has been any other day so far in 2023. There are several factors at play, including a nearby, strengthening low pressure tracking across Ontario, Canada, a strong cold front associated with the low, and changing winds, both in speed and direction, in the lower levels of the atmosphere.
However, there are mitigating factors at play, as well as uncertainties that will not be fully resolved until the storms come this afternoon.
Yesterday, I briefly discussed two primary factors that could help mitigate the severe weather threat somewhat, while still pointing out that isolated to scattered severe storms would be possible even in that environment.
Today, both mitigating factors appear weaker, thus leading to an overall increase in severe potential.
First, I discussed the rain and clouds associated with a warm front. The uncertainty here was the speed with which the front would move through, and what sunshine may result.
Now that the sun is up, the steady rain is already far to the east. The visible satellite, which is just becoming available with the increasing daylight, is showing plenty of clouds, but also numerous breaks in the clouds to our west and southwest.
This should result in a fair bit of heating, which, combined with the soupy atmosphere and other factors, will provide fuel for thunderstorms. Overall, this factor has gone from a potential limiting factor to a “just enough to matter” factor in the severe weather picture.
Second on the list was the winds. More specifically, wind shear. Wind shear is how the wind changes with both speed and direction over a space. For thunderstorms, we care about vertical shear, especially in the lower levels of the atmosphere.
It remains true that the greatest amounts of shear will stay to our south, peaking across the Mid-Atlantic region. However, the shear is a bit more impressive on the model than it was looking, and, like instability, is growing to a point where it matters.
In particular, near-surface shear will be of a more significant magnitude than higher-elevation shear, which does mean we have to consider the chance for a tornado or two. There are other factors at play that also are supportive of tornado potential, though as is the theme for this event, conditions are even better to the south.
Bringing this all together, I am expecting both individual storm cells and small lines of storms to develop this afternoon, possibly in multiple waves. The peak severe weather potential will be between 3-8 PM. Damaging winds will be the primary threat, but a tornado or two is not out of the question. Some localized flash flooding may also result.
A severe weather watch is likely to be issued. Watches mean conditions are favorable for severe weather. I would not be surprised if this watch ends up being a tornado watch, at least for some of our southern counties.
Several severe weather warnings are also likely. Warnings are issued for small areas to address ongoing severe weather associated with individual storms. Both severe thunderstorm and tornado warnings should be taken seriously, especially on a day like today.
Severe thunderstorms can spawn tornadoes with little warning in an environment like this. Furthermore, severe thunderstorms do not need to produce tornadoes to cause significant damage, as was seen in Enfield just two weeks ago when straight-line winds estimated at 100 mph caused major damage.
Severe thunderstorm events in our region are often very complex and involve several factors coming together “just enough” to produce severe weather. As often as this alignment happens, it also just misses, leading to minor or non-events in the region. The slightest deviations one way or another can have major impacts on how the day unfolds.
Therefore, it is important to remain weather aware today, have a plan in place should severe weather threaten, and to be empathetic. If your town does not see severe weather, do not get mad at a “busted forecast”. Be thankful, as someone else in our region may not be as lucky.
I will have some sort of further updates today, so stay tuned.
The Rest of the Week
The low pressure responsible for the severe potential today will still be meandering by tomorrow. Instead of severe thunderstorms, it will be a cool, cloudy day with numerous showers likely.
Scattered showers will be possible Tuesday morning but will become more widespread for the afternoon. A few rumbles of thunder may be possible. With cold air aloft, a little small hail cannot be ruled out completely.
High temperatures on Tuesday will mostly be in the low 70s, though I could see some areas failing to quite make it all the way to 70s degrees.
Wednesday looks mostly dry, though a stay spit of rain in the afternoon cannot be totally counted out. Temperatures should bounce back to the low 80s.
Another front will slide through on Thursday with some showers and storms. At this point, the rain looks scattered. However, there will be strong winds aloft, so any storms that get going will have to be watched closely.
Friday will be another mostly dry day, though, like Wednesday, a stray shower here or there may be possible.
At this time, the weekend is looking unsettled. Showers and storms will be possible on Saturday, again with some wind energy aloft to monitor. Sunday may have some lingering showers. Forecast confidence on both days is low, so continue to check back if you have weekend plans.
There should be little change to the overall pattern as we go through the majority of August.
This graphic represents an average over the entire Finger Lakes region. Localized variations should be expected.
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