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2017 Severe Thread


mappy

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4 minutes ago, supernovasky said:

I'll check them out. I'm really bummed TVN isn't around anymore. I don't think Severestudios is nearly as good.

Yeah, i never followed that stuff much. Was always just a radar watcher and on twitter for updates. 

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Sig Tor is 2.8 for MoCo tomorrow and Supercell Parameters are up to 8, last I checked on the NAM 3km.

 

Hoping we at least have some good severe tomorrow.

 

Will be watching today.

 

@mappy What forums do you usually follow for general threats? I love AmWX here for snow and for DC, but I'd love to know the most active place following today's threat.

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2 minutes ago, supernovasky said:

Sig Tor is 2.8 for MoCo tomorrow and Supercell Parameters are up to 8, last I checked on the NAM 3km.

 

Hoping we at least have some good severe tomorrow.

 

Will be watching today.

 

@mappy What forums do you usually follow for general threats? I love AmWX here for snow and for DC, but I'd love to know the most active place following today's threat.

It's been a long time since we've had one of those multi-model discrete storms merging into a line with pockets of urban flash flooding days.

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ESRL is running the HRRR experimentally out to 36 hours (2x/day, I believe), and the output is at   https://rapidrefresh.noaa.gov/hrrr/HRRR/

The 12z run is pretty insane.   it has the same idea as the 3km NAM parallel nest, with a lead line across the northern burbs that washes out.   It leaves a boundary behind that initiates several elevated supercells, and then a big honking squall line is about to roll through at the end of the run.    Updraft helicity has some nice tracks.

 

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20 minutes ago, supernovasky said:

Sig Tor is 2.8 for MoCo tomorrow and Supercell Parameters are up to 8, last I checked on the NAM 3km.

 

Hoping we at least have some good severe tomorrow.

 

Will be watching today.

 

@mappy What forums do you usually follow for general threats? I love AmWX here for snow and for DC, but I'd love to know the most active place following today's threat.

Well, there is a thread in the Lakes/Midwest subforum following today's stuff. Lots of good posters there

If you are on Twitter --- the ustornadoes twitter has tons of list of pros and amateurs a like that you can follow

https://twitter.com/USTornadoes/lists

Hope this helps! 

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I like the fact that there is no temp inversion tomorrow and 70s make it to the MD line.  Also GFS is wrong, it has spits out bogus orographic qpf over the mountains during some events.  However, lack of clearing maybe a problem and crapvection may still cause issues.

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1 minute ago, high risk said:

ESRL is running the HRRR experimentally out to 36 hours (2x/day, I believe), and the output is at   https://rapidrefresh.noaa.gov/hrrr/HRRR/

The 12z run is pretty insane.   it has the same idea as the 3km NAM parallel nest, with a lead line across the northern burbs that washes out.   It leaves a boundary behind that initiates several elevated supercells, and then a big honking squall line is about to roll through at the end of the run.    Updraft helicity has some nice tracks.

 

That's been honking that scenario since yesterday I believe.

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3 minutes ago, yoda said:

LOL HWO finally mentions that spotter activation will likely be required Wednesday afternoon... and best time threat is 1pm to 9pm... I would argue more like 2pm to 11pm... but whatever

9pm is probably fine unless you're closer to, and east of the bay. Remember that these things once they get rolling tend to unfold a bit faster than expected. Plus, we don't tend to do multiple rounds very well unless they track over different areas. 

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LWX Updated AFD...their language suggests we might wake up with a strongly worded ENH:

 

Quote

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
..Significant weather day expected on Wednesday with strong to
severe thunderstorms...

Cold front will approach the region during the day on Wednesday
with deep moist southwest flow out ahead of the front. Expecting
temperatures to surge well into the 70s to near 80F, with dew
points in the 50s to around 60F, which should help generate 
500-1000 J/KG of MLCAPE. This combined with 0-6KM shear of 60-70
knots and 850-mb flow of 50-60 knots will set the stage for
strong to severe thunderstorm development. 

Exact evolution of thunderstorms will be dependent on how
remnant activity from today plays out, but expecting some
morning activity across our northern zones to give way to main
convective period from about 18z-03z. It should be noted that
some solutions depict an earlier start time, beginning about
16z. Main threat is expected to be damaging winds associated 
with a squall line, but large hail and perhaps an isolated 
tornado are also possible given steep lapse rates and impressive
shear profiles.

Activity will wane Wednesday night following frontal passage.
Gusty northwest winds are expected behind the front with some
upslope rain/snow showers. Lows Wednesday night in the
30s/40s. Cooler and breezy conditions on Thursday.

 

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I think there are 2 fail mechanisms:

    1)  the cloud issue that has been discussed plenty already  limiting instability

    2)  northern lead squall line sends an outflow boundary through the area that wipes out sfc-based instability, although we'd still potentially get a strong elevated squall line (but no sig svr), while we watch supercells roll along that boundary into La Plata

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7 minutes ago, high risk said:

I think there are 2 fail mechanisms:

    1)  the cloud issue that has been discussed plenty already  limiting instability

    2)  northern lead squall line sends an outflow boundary through the area that wipes out sfc-based instability, although we'd still potentially get a strong elevated squall line (but no sig svr), while we watch supercells roll along that boundary into La Plata

We've certainly seen #2 happen, though I wonder if my memory is more focused on stagnant summer-type events than dynamic upper-air events.

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9 minutes ago, high risk said:

I think there are 2 fail mechanisms:

    1)  the cloud issue that has been discussed plenty already  limiting instability

    2)  northern lead squall line sends an outflow boundary through the area that wipes out sfc-based instability, although we'd still potentially get a strong elevated squall line (but no sig svr), while we watch supercells roll along that boundary into La Plata

That happened on June 13, 2013 (http://www.spc.noaa.gov/exper/archive/event.php?date=20130613).  We had a Day 2 MOD that resulted in an early morning YUGE discrete cell which blasted Frederick, Carroll and Howard counties.  It bore several other cells as it raced along I-70 that killed the SC instability.  Eventually, the Day 1 MOD was shifted about 200 miles south and NC got rakked.  A lone cell in West Virginia saved the day for the DC area that afternoon and produced a 20 mile long EF-0 tornado.  I remember it like yesterday because it was my first tornado assessment as an EM with LWX WFO.

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I will be more than happy to have the storms wash out north of Charles County and lay down the boundary across the DC and north area, I also believe that tonight's Ohio Valley convection is going to play havoc with debris clouds. However, I also believe that will be more likely from DC and north. Already some discussion that storms may have trouble initiating in Arkansas. We shall see. Arkansas supercells and upscale growth into Tennessee and then West Virginia/SW VA would be the storms to truly put a cirrus shield overhead here.

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There are cells attempting to fire south and west of Little Rock, those collapse and we have some significant clearing tomorrow. If these cells grow then we have cirrus overhead tomorrow. Whether the dynamics can overcome the lack of surface heating via sunshine remains to be seen. There could be quite a pocket of cold air aloft and lapse rates coming across the Appalachians tomorrow late day. Climatology suggests we should be looking for a conservative solution.

 

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34 minutes ago, Quincy said:

The sig tor potential likely peaks this evening and note that the watch ends at 9 p.m. Look for a downstream PDS tor watch tonight IF storms remain discrete as they move toward the Ohio River and the LLJ really cranks. 

Re Tor Watches #41/#42 (question was asked why not higher tor probs, and this was Quincy's answer)

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1 minute ago, southmdwatcher said:

There are cells attempting to fire south and west of Little Rock, those collapse and we have some significant clearing tomorrow. If these cells grow then we have cirrus overhead tomorrow. Whether the dynamics can overcome the lack of surface heating via sunshine remains to be seen. There could be quite a pocket of cold air aloft and lapse rates coming across the Appalachians tomorrow late day. Climatology suggests we should be looking for a conservative solution.

 

Yeah, but what's the fun in that!? :P

Anyway, it'll be "interesting" to see what happens tomorrow. I'm keeping my feelings in check in regards to tomorrow. But it's difficult, specially when I got that storm in Charlottesville Saturday and was acting like a little kid again. I want that feeling again! :lol:  Then again, I'd be working and would have to do coverage on TV... Doesn't make the storms NEARLY as "fun", honestly. 

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The lack of an esterly component to the surface winds anywhere near here has me a bit excited about tomorrow.  Also  like the fact that there is not a sharp windshift line. That may help keep things more discrete. However, there are still several issues which have been discussed.

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8 minutes ago, WxReese said:

Yeah, but what's the fun in that!? :P

Anyway, it'll be "interesting" to see what happens tomorrow. I'm keeping my feelings in check in regards to tomorrow. But it's difficult, specially when I got that storm in Charlottesville Saturday and was acting like a little kid again. I want that feeling again! :lol:  Then again, I'd be working and would have to do coverage on TV... Doesn't make the storms NEARLY as "fun", honestly. 

I agree, a great supercell is fun to track and watch. They are a spectacular event. As long as it doesn't decide to unload on your backyard with the worst of it's capabilities. Tomorrow still has the chance to be on the higher end of expectations. Severe weather event busts happen in the very short term, both ways.

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