Good evening from Southern Connecticut Weather. 

I am writing a special discussion to provide a deeper analysis on the upcoming days that will have a series of hazards in CT. For our new followers, a SCW Period of Interest is our way of highlighting time periods that bring increased chances of significant weather. It is a way to inform, not panic or hype up.

Let's get right to it. 

Above: the latest National Weather Service (NWS) watches and warnings for the northeast. With the coming heat wave, most headlines are heat advisories or excessive heat watches/warnings to our southwest. Note the expansive flood watch headlines to our north. Although there are no flood watches for CT, this is one of the things we are watching closely for Thursday and Saturday. Image courtesy of Pivotal Weather. 

Thursday--Hazards: Heat, Severe Thunderstorms, Flash Flooding

Heat
A heat wave by itself isn't usually a reason to issue a period of interest, and without the severe weather threat I probably wouldn't be writing right now. That said, people always underestimate heat, and it's actually the top weather related hazard that impacts people's health. 

Today's heat fell just short of 90 with inland highs in the upper 80s. With lower humidity, it didn't feel too bad out there today. That changes in a big way tomorrow, as it is almost certainly day 1 of our heat wave, defined as three consecutive days of high temperatures 90 and above. 

A ridge will bring a plume of heat and humidity over the region, meaning that we will see breezy conditions tomorrow advecting in higher temperatures aloft and at the surface, along with more oppressive humidity. The humidity is a lock, as we're expecting dew points into the 70s again.

Temperatures look to be in the low to mid 90s, and even at the shore you are likely to be close to or over 90 depending on wind direction. It will not feel any cooler given the very high humidity. Heat indices between 95 and 100 are expected statewide, so make sure you are taking precautions if you are outside for an extended period of time.

Temperatures could be a little lower if we have cloud cover hang on from an overnight thunderstorm complex that's expected to die out long before reaching CT, but it's going to be hot regardless. 

Importantly, we will not see much relief Thursday night with elevated temperatures and high humidity. That has a compounding impact on the body. This is nothing new, but it is a reminder to check in on those without air conditioning, especially the elderly. 

Severe Thunderstorms
Tomorrow has the potential to be a very active day across the state, as the Storm Prediction Center (SPC) currently has a slight risk of severe weather for all of Connecticut. This has been up for multiple days, which is uncommon around here. Severe weather is inherently hit or miss, and has felt particularly so this summer where we have had multiple watches and not a lot of severe reports to show for it. 

Every setup is different, and it's important to remember that heading into tomorrow. When we talk about severe thunderstorms, I've heard from some followers that they immediately think of the Midwest storms with violent tornadoes and large hail. That's not what we mean in New England when we talk about virtually all severe weather setups, even the ones with tornado watches, and if the setup were calling for that, rest assured we'd be sounding the alarm. 

Severe thunderstorms are storms that produce winds at or above 58 mph or hail that is quarter size (1") in diameter or larger. Technically a tornado is a severe thunderstorm, but different warnings come out with those. 

Tomorrow is a conditional severe weather day. What does that mean? Most of the ingredients for severe thunderstorms are there. We will likely see unseasonably strong shear as a "cold" front approaches with a weak surface low. We will see sufficient lift come with the same. We will see modest instability build with the heat that we are going to see and more than enough moisture in the air. The ingredients are there for strong to severe thunderstorms.

​How can the severe potential come apart? If we have too much cloud cover that restricts instability from building too high, or if low to mid level lapse rates (change of temperature with height) are weak. 

What makes me perk up a little more for tomorrow is the presence of helicity, or low level spin. Yes, that means an isolated tornado is possible in New England. That's not hype, it's just the reality of the setup. The SPC puts out chances for each hazard (wind/hail/tornado) and as of their latest forecast, wind was at 15%, hail was at 5%, and a tornado was at 2% for most of the state and 5% for the far northern part of the state. Low odds, but enough to take seriously. 

As is usually the case for severe weather, we'll have to watch and see what things look like tomorrow. Storm timing looks to be between 2pm and 10pm with storms traveling from west to east generally. Below is the latest high resolution NAM depiction of noon to midnight tomorrow. Right now I think the best severe chances are north of CT, but any individual storms that develop tomorrow have the chance to quickly become strong to severe. 

I know this is probably already going long, but let me just go one level deeper. 

Above is a high resolution NAM sounding for the Hartford area (it's an averaged sounding) tomorrow afternoon before storms fire up. No, it's not what you'd see in the Midwest, but it is impressive for New England. Why? You have strong helicity (SRH) near the surface along with modest instability (SBCAPE and MLCAPE). There is no cap (CIN) in place to prevent storms from firing, and turning with height looking at the hodograph. That suggests that storms are likely to become strong, and that there is a chance--if what's on paper is actually accurate--that we see severe thunderstorms.

Let's see what it looks like tomorrow. 

Flash Flooding
Finally, the flash flood risk. Not much needs to be said, but it has been all-time wet for many with this being at top 5 wet month at BDL. Although storms are likely to be moving at a faster pace, given the moisture in the air (PWATS over 2"!) any storms are likely to bring torrential rain. For northern CT in particular, that had flash flood warnings yesterday, watch out if you get storms over you. 

One last note on Thursday. It seems a little odd to have severe potential as heat is building into the region. For us "old-timers" it's usually the case that we have storms to break the heat!

​Not this time. ​

Friday--Hazard: Heat

Friday doesn't look like a multi-hazard day, but it may very well be the hottest day of the year. The "cold" front on Thursday doesn't bring anything but more heat and humidity, and Friday is likely to see highs in the mid to upper 90s with heat indices between 95-105. The highest heat index is likely in the heat corridor between Springfield and Hartford, but it's going to be downright brutal across the state. 

While there may be a very slight chance of a storm, I don't think we see much of anything statewide Friday, other than hazy, hot, and humid conditions. This is a day where you definitely want to take it easy if you are outside for any extended period of time. Watch out for pets, children, and the elderly. Unfortunately, the heat does not break Friday night either.  

Make sure you are taking precautions, and watch out for heat related illnesses, which can hit anyone that overexerts themselves outside or doesn't have access to air conditioning. 

Saturday--Hazards: Heat, Severe Thunderstorms, Flash Flooding
Originally, it looked like the cold front that would finally break the heat would arrive on Friday, but that is no longer the case. Now, Saturday is looking like a reflection of Thursday, meaning it will be hot and potentially very active. 

​A powerful cold front is going to bring us relief for Sunday, but first it has to push out the heat. Highs are likely to be in the low to mid 90s, but I'm wondering if Saturday is sneaky hot as the front advances. At any rate, expect heat indices between 95 and 100 again, providing plenty of energy for strong to potentially severe storms. 

Right now, I think the primary risk on Saturday is strong winds and flash flooding as a line of storms associated with the front moves through the state during the afternoon and evening, but this is something that needs to be honed in on later this week. For now, however, the signal is there for another active day. 

Above: Euro depiction of the heat index Saturday afternoon. It'll be another hot day. There is high confidence in that. However, the severe weather potential remains a bit unclear. 

Overall, and active few days are ahead. We'll take it one day at a time here at SCW and will provide updates, but hopefully this gives you information to plan the next few days. 

​A​s always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.

Thank you for reading SCW.

​-DB

Good evening from Southern Connecticut Weather. 

If you like deep summer, this is the best week of the season thus far for summer weather. Let's keep this forecast brief and dive right in. 

Above: GFS Ensemble (GEFS) depiction of the forecast period temperature anomalies nationwide. It'll be a warm week ahead, with the heat peaking on Friday. 

Tuesday
Our quiet conditions probably end tomorrow afternoon, as a mid-level trough brings forcing into the region to allow for more widespread showers and thunderstorms. Most of the day looks fine, but we'll just need to watch the afternoon and early evening for rain chances.

The severe risk looks low, but strong winds and hail, with torrential rainfall are possible in any storms that do develop. Temperatures don't look bad, with highs in the mid to upper 80s. That is normal for late July, which is climatologically speaking our warmest of the year with average temperatures. 

Above: the 18z high resolution NAM depiction of tomorrow between 2-8pm. It obviously won't end up like this, but the depiction shows scattered showers and storms during the afternoon hours, particularly late afternoon and early evening. 

Wednesday-Thursday
Each day this week will get a bit warmer, and Wednesday is likely the start of the heat wave, at least inland.

Believe it or not, despite the high humidity our air temperatures haven't been that hot. In fact, we have only had one official inland heat wave this season--earlier in the month when BDL strung together four days of 90 or higher temperatures. Three consecutive 90+ days are necessary for a heat wave, and we haven't had a lot of 90 degree days this summer.  

A big ridge will bring hot and increasingly humid conditions on Wednesday, with little chance of rain. Thursday, however, will be hotter and potentially more active as a weak system tries to move through the region. As a result, we may get the forcing for strong to severe storms. That's something we'll be watching, but at the very least expect increasingly hot and humid conditions--day and night--especially on Thursday.

We probably see Heat Advisories on Thursday with the heat index between 95-100 degrees. 

Above: the 18z GFS heat index forecast for Friday afternoon. I think this may actually be a bit underdone, and a number of locations may see temperatures in the mid 90s with heat indices over 100 degrees. 

Friday-Saturday
The peak of the heat arrives on Friday, with a strong signal across guidance that virtually all of the state is hazy, hot, and humid with highs in the 90s and dew points in the oppressive range. This may be the hottest day of the year so far, and heat headlines are likely. Heat Advisories are most likely, but if inland areas see highs tick up into the upper 90s, excessive heat warnings are possible. I'd peg that as unlikely for now.

A few days ago, it looked like a strong cold front would arrive on Friday, bringing a chance of strong to severe storms. Now, the guidance has slowed the passage of the front, meaning that Saturday is looking hot as well, though not as hot as Friday right now. Each day will have plenty of sun, but the severe storm threat now looks limited to Saturday as the front approaches. It is something we will be watching. 

Sunday-Monday
If you are longing for the below normal days with lower humidity, Sunday will be your pick of the week. In the wake of the front, I am expecting sunny and cooler conditions with much lower humidity. That relief should actually close out our July on the following Monday as well. 

The Dailies
Tuesday: Mostly sunny and warmer with a chance of showers and thunderstorms in the afternoon/evening. Highs in the mid to upper 80s. Chance of rain 50%

Wednesday: Mostly sunny, hot and humid. Highs in the upper 80s to low 90s. Chance of storms 10%. 

Thursday: Hazy, hot, and humid. Chance of thunderstorms in the afternoon and evening. Highs in the low to mid 90s. Chance of storms 40%. 

Friday: Hazy, hot, and humid. Highs in the mid to upper 90s. Chance of storms 10%. 

Saturday: Hot and humid early with a chance of thunderstorms. Highs in the upper 80s to low 90s. Chance of storms 50%. 

Sunday: Mostly sunny with cooler and less humid conditions. Highs in the upper 70s to low 80s. 

Monday: Mostly sunny. Highs in the low 80s. 

​A​s always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.

Thank you for reading SCW.

​-DB

Good evening from Southern Connecticut Weather. 

As expected, today was an active day with numerous flash flood reports across the state. Despite a tornado warning earlier in the day, all of the tornado warnings were in other states, and at least one tornado was confirmed in Massachusetts. Today, like the other rain events so far in July, was the direct result of an upper level pattern that has been remarkably persistent. Even after this latest heavy rain event, there's no real end in sight to the pattern. Let's dive in.  

Above: a European Ensemble plot predicting another near to above normal precipitation week ahead for New England. 

Monday
Tomorrow we're right back to sunny, hot, and humid conditions. It may actually be the warmest day of the week, with high temperatures inland in the upper 80s to low 90s. It should stay dry, however, in the wake of our latest rain event. We may see some drop in dew points after the boundary passes, but overall it's still humid. The GFS is actually a good example of this, with high dew points dropping in the afternoon only to rise again by evening. That's not much relief. 

Tuesday
Tuesday brings our next chance for rain as another boundary/weak impulse moves into the region. It doesn't look like a washout, but we will see heightened chances of showers and thunderstorms during the afternoon and evening. Temperatures will be in the mid to upper 80s, with humidity levels rising. 

Above: the latest high resolution NAM depicting storm chances on Tuesday. Most of the activity stays north, but we're far enough out to keep watching as the exact result will change. 

Wednesday-Friday
The latter half of the week returns us to the unsettled pattern. The pattern has consisted of frequent impulses "cutting off" over the Great Lakes region, causing air flow to come in from the Atlantic and bring high humidity. It has also kept us from seeing high end air temperatures--the 95 degree days we can see in mid to late July--but it hasn't made much of a difference in sensible weather, as even yesterday we saw lower air temperatures and heat indices in the mid to upper 90s. 

Wednesday and Thursday look mostly quiet. Wednesday should be sunny and warm while Thursday will have a chance of showers and storms typical of summer. Still plenty humid. 

Friday is a day we're going to be watching a little closely, as another system is poised to develop and move to our north. That will once again put us in the warm sector, where bouts of heavy rain and storms are possible. It's still fairly far out, so it's something to casually watch for now. 

Above: the 18z GFS depiction of Friday. It is more robust that the Euro currently, but given the overall pattern, I lean toward a more impactful system than just showers on Friday.

Saturday-Sunday
The last few weekends have had a bunch of question on the weather, and the coming weekend looks no different. We know it'll be humid, but while the GFS has a quiet weekend in the wake of Friday's potential rain the Euro has a boundary on Saturday that gets tied up over the region that would bring lower temperatures and more rain. Not sure which to believe in yet, but again, given the overall pattern it may be good to introduce more rain odds Saturday in case the Friday rain the GFS is highlighting is slower to move in and out. 

The Dailies
Monday: Mostly sunny, hot, and humid. Highs in the upper 80s to low 90s. 

Tuesday: Partly sunny with rising humidity and a chance of showers/storms in the afternoon. Highs in the mid to upper 80s. Chance of rain 40%. 

Wednesday: Mostly sunny. Highs in the mid to upper 80s. 

Thursday: Partly sunny with a chance of showers/storms in the afternoon. Highs in the mid to upper 80s. Chance for rain 30%. 

Friday: Mostly cloudy with rain and thunderstorms. Highs in the low to mid 80s. Chance of rain 60%. 

Saturday: Partly sunny with a chance of rain and thunderstorms early. Highs in the low to mid 80s. Chance of rain 30%.

Sunday: Partly sunny. Highs in the low to mid 80s. 

Finally, while the tropics have been quiet, things may start to heat up in the next few weeks as we start approaching the climatological peak of the season. As you may have heard, there is a lot of uncertainty on what will happen in the Atlantic basin, but as we've seen, it only takes one storm to make a bad season. It's never a bad time to examine your storm preparedness. 

A​s always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.

Thank you for reading SCW.

​-DB

Good evening from Southern Connecticut Weather. 

Today was about as humid as it gets in New England, with some Connecticut stations with dew points in the upper 70s. In fact, the 5pm New Haven observation had a temperature of 86 with a dew point of 77, leading to a heat index of 97!

It has been a wet July, with all of CT well above normal for July to date and with northern CT at or above 300% of normal rainfall for the month. The oppressive humidity--the moisture in the air, sets the stage for what is looking like an active day again tomorrow. 

Above: the Weather Prediction Center (WPC) outlook for tomorrow. Most of New England is under a moderate risk. To be clear, this is very different from the SPC severe thunderstorm outlook, where a moderate risk is a really big deal, but with a WPC moderate risk there is still a 40% chance of flash flooding within 25 miles of a given point. Image courtesy of Pivotal Weather. 

First, this is not the same setup as we saw this past week in Vermont. A combination of long duration rainfall and elevation-related enhancement led to the catastrophic flooding there. 

That said, we have a serious risk of flash flooding on Sunday, especially in the places that have seen the most rainfall recently. In addition, the setup here lends itself to a severe thunderstorm risk, most notably, an elevated risk of a tornado. Let's go into more detail. 

Above: An NRCC plot of the departure from normal for the first half of July. Northern CT through Mass and much of Vermont is 300% or above normal rainfall for the month. 

Overview
All of CT is under a Flood Watch, and the CT River under a continued flood warning as the Sunday setup is a classic heavy rainfall signal.

The obscene moisture we have in the air is the first ingredient. Tomorrow we will see even more which as the NWS notes is near the highest we tend to see in the region climatologically speaking. In addition, we will have a slow moving front and strengthening jet that will act as a forcing mechanism, causing showers and storms to develop and push east toward the region. 

Flash Flooding Potential & Timing
We expect showers and storms to begin developing in earnest between 4-8am, especially in western CT. Over the course of the day and likely into the evening/nighttime hours we will see rain, heavy at times, with embedded thunderstorms possible. It probably won't rain over your house the entire period as you would see with a coastal storm, but when it does rain, it could be very heavy. The WPC has noted that some areas could get rainfall with rates up to 2" an hour. That would likely cause flash flooding given how saturated our soils are. It'd also increase the risk of rivers and streams to rise quickly. 

Overall, we anticipate general rainfall totals between 1-3 inches of rain, but the big caveat is that some areas are almost certainly likely to see higher totals, if not substantially higher totals, based on how many times they get hit with the heaviest convective rains and for how long.

Normally, a standalone 1-3" rainfall isn't worth a discussion of this length, but given the rain we've seen and the potential for higher totals, it's a big enough deal to write about it. This is a shorter duration event thankfully, with the rain expected to end statewide by midnight. The most widespread and heavy rain is likely tomorrow morning into the early afternoon. 

Above: 18z high resolution NAM depiction of the rain tomorrow between 4am Sunday and 2am Monday. This will not be exact, but notice how it has very heavy rain and storms over the state, especially mid morning into early afternoon, followed by another possible period in the afternoon. Where these specific cells of heaviest rain will set up is impossible to pin down with precision. 

Severe Thunderstorm Potential
The SPC has put CT in a marginal risk of severe weather tomorrow, but that doesn't tell the whole story.

In addition to the marginal risk, the SPC has put much of CT under a 2% risk of a tornado. Looking at the setup, it makes sense. We will have heightened shear in the atmosphere as the front approaches. This is significant, as it will allow for more organized storms. That does two things: first, it allows for showers/storms to most efficiently produce rainfall, hence the flash flood threat. The second thing it does is provide a window for strong thunderstorms to rotate.  

As a result, this is something to watch closely tomorrow morning and afternoon. This is more of a conditional threat, meaning that if we don't get another ingredient to reach critical mass, there is no real threat. Tomorrow, we will be looking for instability. We can probably get some strong to severe storms even without a lot of instability, but if we're able to get breaks in the rain and clouds tomorrow to allow for more instability that enhances the risk for strong winds and a potential tornado. This is a little inside baseball, but we also see higher levels of helicity (low level spin) and lower LCLs that could make some thunderstorms surface based, even if briefly. 

The rainfall is the biggest threat, but we will be watching for any quick spin up potential tomorrow any time during the morning and afternoon. 

Above: the SPC HREF Ensemble, showing the mean 48 hour precipitation for this event. It's quite robust, showing the general 1-2" rainfall but even 2.5-3+ inches as a mean in northern CT. That is something to pay attention to. 

Overall
This is the latest in a series of systems that will bring heavy rain to the state. The challenge is that with each successive rain event we increase the chance of flash flooding, and that's the case here.

Areas that see training of cells or extremely heavy rainfall will be at highest risk, and that could be anywhere in the state, though NW CT and northern CT are most likely to get the heaviest rainfall. In addition we have a low, but not zero chance of storms that acquire enough rotation for a quick tornado. This is particularly true if we see higher instability build late tomorrow morning into the afternoon.

It is a day to keep the eye to the sky and radar, and stay away from any flooded roads if you are out. 

​A​s always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.

Thank you for reading SCW.

​-DB