Let's get right to it. Today was a record breaking day in parts of CT, as BDL reported a 99 degree high temperature, breaking the daily record from 1934. In addition, HFD reported 99 and Bridgeport reported 94 degrees. It was a "big heat" day, with widespread highs above 95 and heat indices over 100.
Some guidance continues to show tomorrow being another big heat day, with the favored areas of the Hartford metro area and northern CT River Valley seeing highs in the upper 90s to near 100 tomorrow while the rest of the state sees highs in the 90s. The combination of heat and oppressive humidity will bring heat indices over 100 again tomorrow. The impact of heat on the body gets worse as a heat wave progresses, so take precautions tomorrow and be sure to check on the vulnerable.
Compounding the heat, is the increased risk of severe weather tomorrow. Today's storms were a bit more organized today than expected, and took advantage of the high instability environment to produce significant lightning and strong winds in northern CT. Tomorrow has the potential to be active, as the heat wave breaks in the wake of thunderstorms tomorrow. There are indications that more severe thunderstorm ingredients will be in place tomorrow, particularly in northern CT.
The Storm Prediction Center has issued an enhanced risk for part of northern CT and a slight risk for much of the rest of the state tomorrow.
Let's look at the heat and severe potential in more detail.
As I said above, we're probably looking at another day with highs in the mid to upper 90s. Despite the storms tonight, we will see very warm temperatures overnight, providing a springboard for temperatures to rise fast tomorrow. We should see full sunshine early, followed by increasing clouds in the early afternoon as we start to see instability reach its peak.
We will need to watch the wind direction, which will determine whether we see higher end temperatures or temps a few degrees cooler. Hartford or BDL reaching 100 degrees isn't totally out of the question. Regardless of the air temperature, humidity is expected to be oppressive statewide once again, meaning it's important to take the heat seriously and stay hydrated. Heat indices will be over 100 again.
At the start of the day, the SPC put most of CT in a slight risk for tomorrow, but this afternoon they also added parts of northern CT and points north in an enhanced risk. The ingredients are there for an active day, with strong to severe thunderstorms tomorrow afternoon and evening.
First, we are expecting a moderately to strongly unstable atmosphere. This is measured by CAPE, and the ones I care about most here are MLCAPE (mixed-layer CAPE), and DCAPE (downdraft CAPE). Let's look at an averaged sounding in central CT before storms arrive tomorrow afternoon.
For northern CT, that means we need to watch tomorrow closely as we may see a multi-hazard severe weather threat. Right now, the biggest potential is with strong winds, but there will also be a potential for some hail, heavy rain, and significant lightning. Although the tornado risk is low, it is nonzero in northern CT.
For southern CT, wind, lightning, and heavy rain look to be the potential hazards.
Now, let's be clear: severe weather is inherently localized. Not everyone will see severe weather, but this is the strongest severe weather signal we've seen thus far this season. I do think we see an unstable environment tomorrow and sufficient shear to organize things, but a limiting factor could be timing. The later the storms the less likely they are to maximize potential, though some could still be strong to severe.
Like I said earlier, let's see what the environment looks like tomorrow, but with the combination of heat and severe potential tomorrow is a day where everyone needs to be weather aware. I would not be surprised to see more of northern CT in the enhanced risk zone tomorrow.
To tie it all together, here's the high resolution NAM depiction below. This is between 4-11pm tomorrow, and is not a forecast, but it shows the general idea of what I think will happen. Storms will develop to our northwest during the afternoon and are likely to congeal into a strong line that produces damaging winds and significant rain/lightning.
- Tomorrow is the last day of the heat wave, with highs in the 90s and maximized in central CT with potential highs nearing 100.
- Heat indices will be over 100 again statewide, meaning heat related illnesses are possible. Stay hydrated and check in on the vulnerable.
- There is potential for strong to severe thunderstorms tomorrow afternoon and evening, with the highest severe potential in northern and western CT. Strong to severe thunderstorms are possible across CT.
- Strong winds are the biggest potential hazard, but other hazards such as heavy rain, lightning, hail, and an isolated tornado are possible (especially in northern CT).
- Outdoor activities are possible tomorrow, but keep a close eye to the radar during the afternoon and evening hours.
Thank you for reading.