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5/1 Severe Thunderstorm Threat Discussion & OBS


susqushawn
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...Eastern states...
   Models indicate strengthening of warm sector 850-500 mb wind fields
   to 40-70+ kt during the day today, particularly across the lower
   Great Lakes region, the upper Ohio Valley and the central
   Appalachians into the northern Mid Atlantic Coast region.  This
   should prove more than favorable for organized severe thunderstorm
   development, given at least weak boundary layer destabilization, and
   surface dew points in the 60s probably will contribute to this with
   daytime heating, despite relatively warm and initially capping
   mid-level layers.

   Beneath increasingly difluent flow aloft, frontal and orographic
   forcing for ascent are expected to aid initiation of thunderstorms
   near/east of Lake Erie, southward along the western slopes of
   central into southern Appalachians by 18-21Z.  This activity seems
   likely to eventually consolidate and grow upscale into an organizing
   squall line as it crosses the Allegheny mountains and plateau, and
   to the lee of the Blue Ridge, by early evening.  As it does, it
   probably will be accompanied by increasing potential for damaging
   surface gusts, given the strength of the ambient wind fields, with
   damaging straight line winds becoming the predominant severe threat.
   However, supercell structures, within and perhaps ahead of the line
   as it evolves, may be accompanied by a risk for tornadoes, one or
   two of which could be strong.

   Strong/severe storms may reach the Champlain/Hudson Valleys and Mid
   Atlantic coastal areas by this evening, before weakening within a
   more stable environment.

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That enhanced looks way to bullish to me. Granted we have a s/w moving on through, but the timing looks craptastic. The one they had last night makes more sense to me. I would of maybe went of enhanced to about lns/mdt area then maybe a slgt risk just west of phl then marginal everywhere else. We are lacking instability and are capped a decent amount during the day. There is some good shear and LLJ and a bit of an EML left over to help keep storms going. 

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1 hour ago, tombo82685 said:

That enhanced looks way to bullish to me. Granted we have a s/w moving on through, but the timing looks craptastic. The one they had last night makes more sense to me. I would of maybe went of enhanced to about lns/mdt area then maybe a slgt risk just west of phl then marginal everywhere else. We are lacking instability and are capped a decent amount during the day. There is some good shear and LLJ and a bit of an EML left over to help keep storms going. 

Sometimes high dcape values are an indication that a squall line can just keep on trucking. I thought greater than 1K was ideal, and this one looks like its falling short at PHL (didnt look elsewhere).  Yes this looks about 3hrs too late for prime impact in our area. Much better set-up than Saturday regardless.

Capture.thumb.JPG.a18d3aa543e287e80959b75050866a72.JPG

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1 hour ago, Rainshadow said:

Sometimes high dcape values are an indication that a squall line can just keep on trucking. I thought greater than 1K was ideal, and this one looks like its falling short at PHL (didnt look elsewhere).  Yes this looks about 3hrs too late for prime impact in our area. Much better set-up than Saturday regardless.

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Pretty stout CAP in that sounding. 

Do think the spc enh area is too Far East. Hell, the slight risk is probably too Far East lol. We'll see I guess. We get the lift and good shear today. Just needed saturdays EML/Lapse rates and the cape! 

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25 minutes ago, irishbri74 said:

Pretty stout CAP in that sounding. 

Do think the spc enh area is too Far East. Hell, the slight risk is probably too Far East lol. We'll see I guess. We get the lift and good shear today. Just needed saturdays EML/Lapse rates and the cape! 

We have pretty solid EML during the day, but we are capped 7-7.5 LR is pretty solid around here

nam_2017050106_018_39.93--75.32.png

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2 hours ago, Rainshadow said:

Sometimes high dcape values are an indication that a squall line can just keep on trucking. I thought greater than 1K was ideal, and this one looks like its falling short at PHL (didnt look elsewhere).  Yes this looks about 3hrs too late for prime impact in our area. Much better set-up than Saturday regardless.

 

Yea I'm not arguing for no storms, I just don't see a big severe risk worthy of enhanced or even slgt risk really. This just looks like a general thunder/lighting with a couple stronger storms thrown in. We will see what they do at noon time but I would move everything west

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2 hours ago, irishbri74 said:

Pretty stout CAP in that sounding. 

Do think the spc enh area is too Far East. Hell, the slight risk is probably too Far East lol. We'll see I guess. We get the lift and good shear today. Just needed saturdays EML/Lapse rates and the cape! 

I agree with the westward shift that SPC made with the latest outlook. This may be a switch of what occurred Saturday (with dew points being fcst too high), doubt we are that cool (sfc) by 8 pm on that sounding. Regardless this looks late to the party for us.  Ok enough short wave to think that this will have more eastward sustainability than average.  April/May convection is like December snow, its nice if it happens, but its not the meat of our season.  Come Memorial Day....

 

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82F in West Chester with a delicious 68F dewpoint.

I'm entertaining myself by watching the PA Turnpike cameras as the front rolls through and the images turn from sunny dry concrete to ominous dark clouds to 0.1 mile visibility in rain.  Don't judge me! B)

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1 hour ago, cbelke said:

Still fairly cloudy here, made it to 76F. Probably not enough to provide any major destabilizing of the atmosphere around the general area.

Destabilizing was always an issue, CAPE was virtually nothing. For us it's all being driven by the s/w moving in with strong LLJ, shear, and somewhat of an EML left. 

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8 minutes ago, mshaffer526 said:

Looking at the radar, hard to foresee a concrete line even making it to LNS.  Just talked to my mom in Altoona, she said that was the heaviest rain she's seen in some time.

PWATS are pretty high for this time of the year, so that makes sense

hrrr_pwat_pennsylvania_1.png

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