2018 Mid-Atlantic General Severe Discussion

[Eskimo Joe]

Unpopular opinion:  SPC is pretty meh at SWODx for the Mid Atlantic and Northeast.  I find them to be too hypey for this part of the country.

[Kmlwx]

19 minutes ago, Eskimo Joe said:

Unpopular opinion:  SPC is pretty meh at SWODx for the Mid Atlantic and Northeast.  I find them to be too hypey for this part of the country.

Honestly I feel like I've seen it go both ways. We've had plenty of days of being in a low end slight or "See Text" before marginal was a thing that turned out to be pretty impressive days (nothing derecho - but just higher end stuff in general). 

On the flip side - we've definitely seen days of high end slights or even moderates go completely up in smoke. Usually it's cloudcover or capping or whatever. Always something to blow the forecast. 

[Eskimo Joe]

2 minutes ago, Kmlwx said:

Honestly I feel like I've seen it go both ways. We've had plenty of days of being in a low end slight or "See Text" before marginal was a thing that turned out to be pretty impressive days (nothing derecho - but just higher end stuff in general). 

On the flip side - we've definitely seen days of high end slights or even moderates go completely up in smoke. Usually it's cloudcover or capping or whatever. Always something to blow the forecast. 

It's a challenging area to be sure.  Case in Point:  Derecho 2012.  That was a vastly under-forecast event with significant consequences.  In fact tomorrow is the 6th anniversary of the event. But it seems that 8/10 times SPC forecasts a ENH or MOD risk it's maybe on cell that gets beefy and the rest of the area is uber meh. 

[Kmlwx]

6 minutes ago, Eskimo Joe said:

It's a challenging area to be sure.  Case in Point:  Derecho 2012.  That was a vastly under-forecast event with significant consequences.  In fact tomorrow is the 6th anniversary of the event. But it seems that 8/10 times SPC forecasts a ENH or MOD risk it's maybe on cell that gets beefy and the rest of the area is uber meh. 

May just be selective memory - but I feel like mod risks bust for us less often than ENH. I think they are way more willing to throw out an ENH vs a moderate for us - they are (with a few exceptions) only willing to put out a mod for us when something like a derecho or high end tor risk day seems in the bag. 

[frd]

1 hour ago, Eskimo Joe said:

Unpopular opinion:  SPC is pretty meh at SWODx for the Mid Atlantic and Northeast.  I find them to be too hypey for this part of the country.

Looks like nationwide low tornado count ?  Any ideas ?

And looking at the sun love seeing the sharp declines in output as we approach the solar min.  

[Eskimo Joe]

50 minutes ago, Kmlwx said:

May just be selective memory - but I feel like mod risks bust for us less often than ENH. I think they are way more willing to throw out an ENH vs a moderate for us - they are (with a few exceptions) only willing to put out a mod for us when something like a derecho or high end tor risk day seems in the bag. 

The last MOD we had was June 2013 that busted horribly.  It was eventually shifted well south into North Carolina.

[George BM]

Not an expert but... a hypothesis of mine is that the dynamics that would warrant us being under a higher risk (particular with west to east ring of fire type low pressure systems ) often allow the previous day's storms, which would otherwise die out and leave us with only nuisance cloud debris that morning, to survive the overnight trek through the Ohio Valley and cross the Appalachian Mountains into our region by or just after dawn (June 13, 2013,... June 23, 2016 (though that event might've been a wee bit south to start)) and mess up our instability by shifting it south. Sometimes it can take longer than modeled or longer than the SPC anticipated for the atmosphere to recover enough to allow for good afternoon/evening storms for us.

With the deeper troughs that can warrant higher risk days for us cloud debris from storms that outrun the cold front and/or the lift available in general can often lead to cloud cover that is extensive enough to tamper down the intensity of storms that form from what was expected though the strong lift, especially near the front, can still allow storms to form more often than in the case above. 

Like I said I'm no expert. I'm just an amateur and this is my opinion based on what I've observed over the past several years. Weather is very complicated and I know that there are many other variables to consider that I didn't touch on. 

[AfewUniversesBelowNormal]

Nothing really in sight thunderstorm wise, drier pattern under the ridge and the flow remains SE off the Atlantic 

[WeatherLovingDoc]

6 hours ago, Eskimo Joe said:

The last MOD we had was June 2013 that busted horribly.  It was eventually shifted well south into North Carolina.

Rarely post, but do wonder if high temps might not come to fruition in NE, including Mid Atlantic. Any insight americanwx.com? What are mitigating factors?

[Eskimo Joe]

13 hours ago, WeatherLovingDoc said:

Rarely post, but do wonder if high temps might not come to fruition in NE, including Mid Atlantic. Any insight americanwx.com? What are mitigating factors?

IMO, clouds and small scale features like bay breezes, terrain, etc.

[MN Transplant]

17 hours ago, WeatherLovingDoc said:

Rarely post, but do wonder if high temps might not come to fruition in NE, including Mid Atlantic. Any insight americanwx.com? What are mitigating factors?

It depends on what your baseline is.  The GFS is wrong, so don't use that.  Otherwise, the forecast isn't really that special (95,97,95 near DCA).  The mitigating factor in the DC area is that we've been so wet.  That hasn't been the case in New England. 

[Eskimo Joe]

21 hours ago, MN Transplant said:

It depends on what your baseline is.  The GFS is wrong, so don't use that.  Otherwise, the forecast isn't really that special (95,97,95 near DCA).  The mitigating factor in the DC area is that we've been so wet.  That hasn't been the case in New England. 

Plus it's not that warm at 850mb.  We typically need widespread +23 degree air and we just don't have it this summer.  We're stuck in this perpetual cool pattern that we can't shake.

[Kmlwx]

WTOP weather forecast mentioned storms with damaging winds and flooding rains for tomorrow - SPC is not impressed lol. 

[yoda]

Hmmmm... from morning AFD from LWX:

Higher resolution convective allowing models also depict a
potential convective system emerging from this afternoon`s
convection across OH/PA. This may approach eastern WV/MD by
later this evening, and will have to be monitored for potential
severe activity. Model forecast soundings also depict weakening
of cap along the I-95 corridor by late in the evening and into
the overnight so chances for showers/thunderstorms actually
increase there towards and after sunset.

[JWilliam9830]

18z NAM has a nice blow-up of storms around 18z tomorrow.

 

 

[nw baltimore wx]

1 hour ago, JWilliam9830 said:

18z NAM has a nice blow-up of storms around 18z tomorrow.

Most of the guidance from the gfs and nam that I've seen over the past five or so days shows those storms developing along and east of 95 leaving the corridor between 81 and 95 void of any appreciable rain. 

I'm not saying that'll happen, but I'm tempering any enthusiasm. Hopefully we all get a soaker tomorrow.

[Abbyme24]

20 hours ago, nw baltimore wx said:

Most of the guidance from the gfs and nam that I've seen over the past five or so days shows those storms developing along and east of 95 leaving the corridor between 81 and 95 void of any appreciable rain. 

I'm not saying that'll happen, but I'm tempering any enthusiasm. Hopefully we all get a soaker tomorrow.

Looks like you may have been right, unless another line of storms is supposed to develop later.

We've been getting screwed over in NW baltimore the past few weeks. What little thunderstorms we've had either miss us or barely graze us. 

[frd]

Appears to be some potential on this Friday,  although as usual there are a few factors that reduce that potential.  

[Kmlwx]

Per the obs thread - slight risk already in place for Friday from roughly DC and then to the north and east. 

Day 3 risks are fraught with potential to bust

[87storms]

2 minutes ago, Kmlwx said:

Per the obs thread - slight risk already in place for Friday from roughly DC and then to the north and east. 

Day 3 risks are fraught with potential to bust

i'm not finding this to be a particularly impressive severe season at all.  i guess we've had a few storms, but not imby.  last year seemed better overall.

[Kmlwx]

36 minutes ago, 87storms said:

i'm not finding this to be a particularly impressive severe season at all.  i guess we've had a few storms, but not imby.  last year seemed better overall.

Yeah I'm snoozing so far this summer on severe. Granted, I've been busy with work and I moved... But I have not been impressed IMBYs

[87storms]

9 hours ago, Kmlwx said:

Yeah I'm snoozing so far this summer on severe. Granted, I've been busy with work and I moved... But I have not been impressed IMBYs

we've done much better in the rain department than the squall department.

[Amped]

This pattern isn't exactly in a hurry to stop

[JakkelWx]

TWC highlighted that there could be a bullseye for severe weather from D.C to Baltimore, because of a southerly flow from the southeast and the jet stream from the west.

Edit: D.C to Philly, including baltimore. Along the Mid-Atlantic part of the I-95 big cities.

[Kmlwx]

19 hours ago, Amped said:

This pattern isn't exactly in a hurry to stop

The rain pattern? Or the lack of severe pattern? 

[biodhokie]

18 minutes ago, Kmlwx said:

The rain pattern? Or the lack of severe pattern? 

yes.

[high risk]

I think I'm IN for Friday.    Latest NAM3 and HRRR show fairly widespread storms in the very late afternoon  / early evening hours, especially along and north of I-66 in VA and Rt. 50 in MD.   Forecast soundings show ~2500 j/kg of sfc-based cape with modest lapse rates.    Low-level shear is weak, but deep layer shear appears to be sufficient for SVR, given the moderate instability.

[yoda]

2 minutes ago, high risk said:

I think I'm IN for Friday.    Latest NAM3 and HRRR show fairly widespread storms in the very late afternoon  / early evening hours, especially along and north of I-66 in VA and Rt. 50 in MD.   Forecast soundings show ~2500 j/kg of sac-based cape with modest lapse rates.    Low-level shear is weak, but deep layer shear appears to be sufficient for SVR, given the moderate instability.

I know I posted them in the July discobs thread... but what do you think of the 00z NAM and 00z 3km NAM soundings at DCA for 00z SAT?  According to the possible hazard type, both show TOR... guess there might be a slight chance for a weak spinup?

[high risk]

27 minutes ago, yoda said:

I know I posted them in the July discobs thread... but what do you think of the 00z NAM and 00z 3km NAM soundings at DCA for 00z SAT?  According to the possible hazard type, both show TOR... guess there might be a slight chance for a weak spinup?

      I commented in the other thread, but I think that the backing of the sfc winds isn't likely.   The NAM nest only backs them along an outflow boundary from initial storms (so it would have to be completely nailing the evolution to be correct), and the HRRR doesn't back them at all.    The NAM12 actually has widespread backed sfc winds, but it's an outlier.     I guess I won't totally rule it out, but I'm not seeing this as tornado threat unless the NAM12 is correctly showing the widespread southeast sfc winds.

[Ellinwood]

My thinking is very much in line with high risk's... I'm hyped in terms of general severe chances, mainly for the northern MD to DC crew. Tornado threat is very limited... mainly up the waterways that can hold a better sustained southerly surface wind. Winds from 700mb down aren't great, but from 500mb up are good. Leaning toward the area not seeing much activity before 5pm, but wouldn't be surprised to see showers and storms popping as early as 2-3pm. Main show being the line of storms in the evening.

Was surprised to not see a local ENH risk for DC to southeastern PA... the northern MD and DC crew could/should be the jackpot areas today. We'll see if it can get organized early enough to give parts of NoVA a show as well.