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wdrag

SVR potential late Wed-Thu August 26-27 NYC metro

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Uncertain, but at least one other on our forum has been onto the potential for a couple of days and I agree.  Instability in low level WAA (strong warm front) beneath a decent nw flow mid level jet should permit a couple of episodes of nw flow severe thunderstorms.

The first, sometime late Wednesday or Wed night through PA and possibly western NJ (plus see SPC D3 issued early Monday morning).  I didn't expect to see a Marginal risk this far east into NJ but it is possible and I defer to the SPC D3. 

The second episode sometime Thursday, when it appears the risk shifts into our area.  Best axis Thursday?  Suspect close to the warm front which should be se NYS/NJ/ne PA.

It's late in the season for this this... so I express a little caution for this possible late summer convective event. 640A/24

 

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Good Tuesday morning everyone,  SPC has a long corridor of Slight Risk severe weather potential across the northern USA Thursday.  They pulled back Wednesday's out of our area and this makes sense based on the 00z/25 modeling.  As far as Thursday goes...please see SPC D3 discussion. 604A/25  At 825A, I added the D3 SPC outlook and here's what they said near 0739z/25 (339AM EDT).  I underlined the last line! 

 ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN
   PLAINS INTO THE GREAT LAKES AND NORTHEAST STATES...

   ...SUMMARY...
   Severe storms are possible Thursday from a portion of the northern
   Plains through the Great Lakes and Northeast States. Damaging wind
   and large hail are the main threats. A few tornadoes will also be
   possible over the lower Mississippi Valley region.

   ...Lower Great Lakes through Northeast States...

   Early Thursday morning a warm front will extend from northern NY
   southeast into southern New England. This boundary will move east
   during the day, while a cold front advances southeast through the
   lower Great Lakes reaching the Northeast States by late Thursday
   afternoon. Elevated storms should be ongoing within zone of ascent
   on cool side of the warm front from northern NY into New England.
   Overall severe threat with this activity will probably remain
   limited. In wake of morning storms and the passing warm front, the
   advection of rich low-level moisture with upper 60s F dewpoints and
   diabatic warming should result in moderate instability with
   1500-2500 J/kg MLCAPE possible. Additional storms will likely
   develop along lake breezes and approaching cold front and spread
   southeast through a portion of the Northeast States. This region
   will remain within belt of stronger northwesterly winds aloft with
   40-50 kt effective bulk shear supporting fast-moving organized
   storms including bowing segments and supercells. Have introduced a
   sig area this update, and an upgrade to higher probabilities will
   likely be needed in day 2 updates.  

Screen Shot 2020-08-25 at 8.22.39 AM.png

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Extracted from the tropical topic:  

A period of WAA showers/elevated isolated thunderstorms early Thursday north of I78 for much of the forum, then the potential nw flow severe weather event sometime between 4P and midnight late Thursday.  KI 35-40 late Thursday and PWAT temporarily up to at least 1.8. Plenty of wind aloft and see SPC. Should be steamy  in NYC Thu afternoon (HI 95-100?)  827A/26

Screen Shot 2020-08-26 at 4.40.01 AM.png

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Could be a very active day tomorrow. Not often that we have a hatched wind and hail area right down to the coast here. Also 5% tornado threat so that has to be looked at too. 

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1 hour ago, jm1220 said:

Could be a very active day tomorrow. Not often that we have a hatched wind and hail area right down to the coast here. Also 5% tornado threat so that has to be looked at too. 

Trigger isn’t very apparent, I guess the backdoor front but models are all over the place on it

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3 hours ago, qg_omega said:

Trigger isn’t very apparent, I guess the backdoor front but models are all over the place on it

looks like it will be where ever the thermal boundary sets up...models erratice but focusing on central CT right now for the best storms

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The warm front has to move through and clear things out. 

Convection this afternoon should be isolated thanks to the EML that will move through.

06z 3k NAM soundings indicate SBCAPE values in excess of 2000 J/KG by 18z. Modest shear values along with steep lapse rates and instability should support the development of multicellular activity and isolated super cells. Main threats will be unusually large hail, damaging winds and an isolated tornado or two. Certainly understand why SPC has had our area in an enhanced risk.

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Any idea about what time to expect thunderstorms and high winds in Nassau County LI?

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36 minutes ago, forkyfork said:

we're too far away from the warm front imo

So another bust incoming? Horrible 

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The line from Syracuse to Albany is the area to watch. SPC just issued a MCD stating that it's heading into a better environment and will likely become surface-based soon.

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Looks like a hail/ wind risk to me. I don't see much low level speed/directional shear... but i do see mid level speed/ directional shear and impressive lapse rates. We shall see how it evolves.

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I’m in the Southampton area, what should I expect here later tonight? Anyone with more knowledge could you give me a more detailed forecast?

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Time on family wedding vacation for a quick post: Am adding some HRRR gust forecast data for now through 10P, then for Friday afternoon.  Max Gusts..see 40-50kt via legend. 

Also adding 80m wind forecast for CT-LI area late today to show the backdoor cold front-thunderstorm aided southward progression. This front could nix svr risk for LI/CT tomorrow afternoon but NJ I think has a pretty decent chance of SVR Fri afternoon and maybe the SPC D2 risk may be advance northward there in tomorrows update.

In the meantime, expecting lots of svr for NYC forum through 9PM today.. even e LI where best chance of rotation is modeled in the HRRR. PWAT up to 2".  Lowest chance svr through this eve, I think is Ocean-Mercer I195 area.

Fri: potent on the warm side of the front as exampled in some of the modeling for tomorrow.  

Fri night: difficult to see this as a quiet night. KI very high at night. Could be a few 1-3" clusters..PWAT 2"+

Sat: while Laura goes out somewhere through S VA-DE... there should be more convection along the cold front!

 

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Screen Shot 2020-08-27 at 1.47.27 PM.png

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40 minutes ago, wizard021 said:

Mean looking couplet near Hobert NY

Looks like that was occluding and I would expect a new one to form to the NW of that one.

Scratch that. Maybe not.

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Looks like the main threat area will be the Hudson Valley, but we could also get some severe into Northeastern NJ and Long Island.

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