Saturday, July 18, 2026 Thunderstorm/Severe Weather Potential

[weatherwiz]

An unseasonably strong shortwave trough amplifies as it swings across the Great Lakes region on Saturday as it advances towards the Northeast Saturday evening/overnight. As it does so, a cold front will push across the Great Lakes region during the day with a warm front lifting across the Northeast during the day on Saturday ushering in a warmer and more moist low-level airmass. Ahead of the trough features 40-45 knots of westerly mid-level flow with 30-40 knots of southwesterly flow in the lower-levels of the atmosphere which will contribute to 30-40+ knots of bulk shear, sufficient for storm organization. 

With the warm front approaching and a relatively uncapped airmass, extensive cloud cover along with scattered showers and thunderstorms are expected throughout the day and this does raise concerns about how much surface heating can occur and how much instability can build. Secondly, the timing of the rain and thunderstorms associated with a pre-frontal trough will be during the early evening, after peak heating. While instability would be a concern moving out of peak heating, as the warm front continues lifting through the region, the advection of higher theta-e air should help maintain what instability we have in place or even boost instability values a bit. 

CAMS are rather bullish in developing multiple rounds of thunderstorms across NY and PA with potential for multiple and concentrated swaths of damaging wind gusts and even potential for a few tornadoes given high helicity values. CAMS weaken this activity as it propagates across New England during the evening, however, given strong dynamics, increasing height falls, and at least weak instability (MLCAPE ~1000 JKG), localized damaging wind gusts and perhaps even an embedded tornado would remain possible as this activity crosses the region. As usual, the best potential for damaging winds or a tornado would be western sections. If instability turns out greater than forecast, there would be potential for a greater damaging wind threat across western MA and western CT.

[weatherwiz]

18z HRRR pretty ominous 

[Modfan2]

27 minutes ago, weatherwiz said:

18z HRRR pretty ominous 

For who?

[weatherwiz]

3 minutes ago, Modfan2 said:

For who?

To our west but also within CT along the warm front during the afternoon with potential for supercells/isolated tornado risk. 

Then a line moving through during the evening with localized wind damage threat 

[Cyclone-68]

Not hatched but a 5% tornado threat in NYS

[WxWatcher007]

8 minutes ago, weatherwiz said:

To our west but also within CT along the warm front during the afternoon with potential for supercells/isolated tornado risk. 

Then a line moving through during the evening with localized wind damage threat 

Might be some flood risk if those storms train in CT. 

[weatherwiz]

4 minutes ago, WxWatcher007 said:

Might be some flood risk if those storms train in CT. 

yeah certainly could see some flash flooding 

[CoastalWx]

10 minutes ago, weatherwiz said:

yeah certainly could see some flash flooding 

Locking in Southbury to Seymour for that.  

[CoastalWx]

WF action along it. Definitely good shear in place too. Probably pike south deal. Evening stuff maybe best in western areas.

[Cyclone-68]

Doesn’t have to be an Iowa derecho just give me a GD thunderstorm 

[Sey-Mour Snow]

53 minutes ago, CoastalWx said:

Locking in Southbury to Seymour for that.  

You know it 

[CoastalWx]

4 hours ago, Cyclone-68 said:

Doesn’t have to be an Iowa derecho just give me a GD thunderstorm 

Probably won’t happen 

[WinterWolf]

7 hours ago, Sey-Mour Snow said:

You know it 

We’ve been wet for sure…your area SW of here even a bit more…but all of us WOR have gotten our share.  We’ll see what later today brings. 

[Damage In Tolland]

Everything severe wise seems wagons south . Like South of 84. Hopefully this is not another miss with light showers 

[Torch Tiger]

Looks steined up this way. Good luck to west/south

[WinterWolf]

13 minutes ago, Torch Tiger said:

Looks steined up this way. Good luck to west/south

Thanks. 

[wx_observer]

SPC moved the severe threat a bit further east on update:

Update:

 

Previous

[WxWatcher007]

18 minutes ago, wx_observer said:

SPC moved the severe threat a bit further east on update:

Update:

 

Previous

And not just the overall categorical risk. The 5% tor and wind has been pulled east as well. 

[WinterWolf]

11 minutes ago, WxWatcher007 said:

And not just the overall categorical risk. The 5% tor and wind has been pulled east as well. 

Here we go…Sun trying to pop here now. 

[WxWatcher007]

Just now, WinterWolf said:

Here we go…

[WxWatcher007]

Some pretty nasty supercell and sig tor numbers for western CT and points west on the 12z 3K Nammy. Soundings for HFD, BDL, and BDR. I'm still fairly skeptical of high end stuff here but I think it's an active day. 

[WinterWolf]

Being well west of BDL, and west of Hartford, gotta keep an eye here it looks like. 

[Damage In Tolland]

54 minutes ago, WxWatcher007 said:

Some pretty nasty supercell and sig tor numbers for western CT and points west on the 12z 3K Nammy. Soundings for HFD, BDL, and BDR. I'm still fairly skeptical of high end stuff here but I think it's an active day. 

What do you think on timing?

[weatherwiz]

Definitely going to be interesting early evening, guidance increases instability just out ahead of the main activity moving in. If we can get upwards of 1500 J of MLCAPE to build in like some guidance shows there will be some wind damage for sure. Of course given the directional shear there would be the risk for a few tornadoes. Won't be getting much sun today but our instability is going to be coming from increasing dewpoints...if we get dews 73-74-75 in...watch out

[WxWatcher007]

20 minutes ago, Damage In Tolland said:

What do you think on timing?

Discrete this afternoon, the line this evening. 

[LSC97wxnut]

Not sure which thread to put this in, but are the storms in New York all there is for today, or are those supposed to die off and we'll see more later?

[weatherwiz]

7 minutes ago, WxWatcher007 said:

Discrete this afternoon, the line this evening. 

I think our window for discrete may be smaller and probably would be timed closer to when the line arrives. Probably looking at 5-7 for discrete with the line rolling through shortly after. I think the overall progression of the warm front has slowed to what it was looking like yesterday. It will be some time before we can get in some sfc instability 

[Modfan2]

NYC getting some heavy cells at the moment 

[WinterWolf]

9 minutes ago, weatherwiz said:

I think our window for discrete may be smaller and probably would be timed closer to when the line arrives. Probably looking at 5-7 for discrete with the line rolling through shortly after. I think the overall progression of the warm front has slowed to what it was looking like yesterday. It will be some time before we can get in some sfc instability 

Some nasty stuff up around Rochester…wonder if that is what comes through here this evening?  

[weatherwiz]

4 minutes ago, WinterWolf said:

Some nasty stuff up around Rochester…wonder if that is what comes through here this evening?  

yup...that's the stuff to watch for this evening. As that activity approaches we may see some discrete develop out ahead of it.