Thursday, July 27, 2023 Severe Weather Potential

[weatherwiz]

Potential exists Thursday for widespread thunderstorms to propagate in a west-to-east fashion across the region late afternoon through mid-evening; including the possibility for numerous strong-to-severe thunderstorms which will be capable of producing damaging winds and/or hail with a few tornadoes also possible. 

Note: Model graphics being used but not mean that model is being favored, the product is just being used for illustrative purposes. 

Forecast models are in agreement that an unseasonably strong shortwave energy embedded within seasonably strong jet traverses New England during the late afternoon and early evening. Forecast models differ within just how strong this shortwave energy will be which will determine the overall strength of the shear.

A warm front lifts northeast across the region during the morning resulting in a surge of high llvl theta-e air characterized by surface dewpoints climbing into the lower 70's. This combined with surface temperatures climbing into the 80's should contribute to a moderately unstable airmass with MLCAPE values as high as 1500-2000 J/KG. One determent to stronger instability may be the mid-level lapse rates. H7 temperatures are forecast to be around +10C with H5 temperatures only around -8C. Forecast model soundings show some warm pockets aloft which would lead to weaker mlvl lapse rates and could prevent stronger instability from materializing. 

As mentioned above, dynamics should be rather strong (just a question of how strong) with H5 jet of 40-60 knots and a llvl jet in excess of 30-40 mph resulting in a good deal of speed shear. With the warm front nearby, sfc winds will be more S to SSE with winds changing with direction with height through the troposphere. Winds increasing with speed with height (speed shear) combined with winds changing direction with height will contribute to large hodographs. 

As the shortwave approaches, numerous thunderstorms should develop by mid-to-late afternoon and traverse the region through the mid-evening before exiting the coast. Combination of strong wind shear, strong forcing from the shortwave, and moderate instability should yield numerous strong-to-severe thunderstorms which will be capable of producing damaging wind gusts, large hail, and even a few tornadoes. In the event we can materialize steeper mid-level lapse rates a higher end severe threat could materialize. 

[Torch Tiger]

...Northeast into the Mid-Atlantic states...
   Scattered showers/thunderstorms will probably be ongoing Thursday
   morning across western/northern NY in association with a LLJ.  A
   seasonably moist boundary layer is forecast to over the entire
   region and cloud breaks/heating will likely lead to moderate
   destabilization across much of southern New England.  As a weak
   capping inversion erodes by midday, scattered to numerous storms
   will likely form by early-mid afternoon.  Appreciably strong low to
   mid-level flow fields indicated by some model guidance lends
   concerns for both severe gusts with an organizing band of storms,
   and some potential for storm-scale rotation via cellular or linear
   modes.  Farther south into the Mid-Atlantic states, weaker
   large-scale ascent will partially be offset by very warm/humid
   conditions in lee of the higher terrain for storms to initiate. 
   Damaging gusts and perhaps large hail with the heavier cores are
   expected through the early evening.  

[Chrisrotary12]

Not sure I love the timing for areas east of Springfield.

[ineedsnow]

18z NAM gone wild

[weatherwiz]

Well if we can get dews in the 73-76 range that would compensate for poor mlvl lapse rates 

[Typhoon Tip]

The Michigan 24-hour teleconnector for severe in this type of set up

[WxWatcher007]

1 hour ago, Typhoon Tip said:

The Michigan 24-hour teleconnector for severe in this type of set up

What is that?

[STILL N OF PIKE]

14 minutes ago, WxWatcher007 said:

What is that?

If S Michigan sees severe weather , SNE has a higher chance of seeing the same 24 hrs later 

prime example is the June 8 1953 F5  Flint  Michigan Tornado one day prior to the infamous Worcester tornado . Flint tornado killed over 100 and ORH one was an F4 and killed at least 94 . Almost unimaginable in my opinion .

[ineedsnow]

Still some uncertainty for tomorrow  but could be good

[dryslot]

Going to be tough here tomorrow matching last nights storms but probs are quite high.

[weatherwiz]

May see an upgrade to enhanced. Could see a decent swath of wind damage reports. 

[WxWatcher007]

12 minutes ago, weatherwiz said:

May see an upgrade to enhanced. Could see a decent swath of wind damage reports. 

Looks like the bulk of the activity is pike north on the guidance. Pretty good BOX discussion this morning.

[weatherwiz]

1 minute ago, WxWatcher007 said:

Looks like the bulk of the activity is pike north on the guidance. Pretty good BOX discussion this morning.

Tomorrow may favor eastern areas (say east of 84) but I would not count eastern CT out. Have to closely assess this more a bit later on but there seems to maybe some some capping or maybe some subsidence issues in CT but activity could develop very quickly east of the river.

[Torch Tiger]

 awful ML lapse rates combined with cloud debris/garbage can ruin it

[weatherwiz]

Just now, Cyclone-68 said:

Ten percent?? Yikes. Gotta figure tornado watch IF everything comes together as planned 

That was from 2010

we have 5% tomorrow

[Cyclone-68]

4 minutes ago, weatherwiz said:

That was from 2010

we have 5% tomorrow

Ahhh.. Sorry lol.. I will delete 

[CT Rain]

7 minutes ago, Torch Tiger said:

 awful ML lapse rates combined with cloud debris/garbage can ruin it

lol what a disaster that was

[weatherwiz]

Just now, CT Rain said:

lol what a disaster that was

At least there were some microbusts that weekend. Wasn't there also a macrobust too? 

[Chrisrotary12]

Ok. Now I am intrigued. Timing for tomorrow has sped up in hi-res guidance. nice!

[weatherwiz]

Just now, Chrisrotary12 said:

Ok. Now I am intrigued. Timing for tomorrow has sped up in hi-res guidance. nice!

Indeed, quite a bit actually. This could end up being pretty nasty across northeast MA. 

[HoarfrostHubb]

I thought the mesos (12z HRRR, 3k and 12k NAM) looked kinda meh

[ineedsnow]

7 minutes ago, HoarfrostHubb said:

I thought the mesos (12z HRRR, 3k and 12k NAM) looked kinda meh

Compared to yesterday they were

[Cyclone-68]

New Day 2 outlook due at the bottom of the hour 

[Cyclone-68]

No changes on the latest update 

[Chrisrotary12]

Not obvious to me that it changed at all.

[weatherwiz]

Looks like capping around 500mb and quite a bit of dry air aloft may be big inhibitors tomorrow say south of the Pike. 

I'm leaning towards a scenario tomorrow where we see discrete supercells develop across eastern NY and move into VT, MA, and NH with activity organizing into a line towards eastern sections. The forcing is really tied into the strong shortwave with not much frontal forcing (no real cold front pushing east). Given the degree of wind shear, both speed and directional, the degree of forcing we will have should favor a discrete storm mode. There may be enhanced forcing farther east (sea-breeze) which may help activity consolidate some. 

I am very uncertain as to what to expect south into CT, but I think the seabreeze front should act least act as a initiator. 

[Chrisrotary12]

The Detroit bow is either going to throw on a blinker and turn left into Canada or its going to progress into areas not within SPC's outlook. 

[weatherwiz]

5 minutes ago, Chrisrotary12 said:

The Detroit bow is either going to throw on a blinker and turn left into Canada or its going to progress into areas not within SPC's outlook. 

I wonder if it follows the instability gradient and ends up progressing into areas not within the Outlook

[Damage In Tolland]

Man.. big big day tomorrow all of SNE down to NJ

[weatherwiz]

Similar setup Saturday too.