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2021 Mid-Atlantic Severe Weather - General Discussion


Kmlwx
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1 hour ago, Eskimo Joe said:

Sterling seems pretty bullish about tomorrow. Curious as to what they are seeing to make them so.

I seem to remember a few sporadic severe days in our area over the years that had them really using ominous language for a rather "standard" event. 

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I was just playing around with the SPC Severe Event Archive. Something I did not realize is that if you put in MD as the selected state. The September 24th 2001 event (College Park TOR) is the event immediately before April 28th 2002 in the archive. Not terribly impressive since September is a fair timeframe for our last severe event of the season, and April for the first. But to have two such memorable events right next to each other in the archive stood out to me. 

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6 hours ago, yoda said:

Afternoon AFD has no mention of anything for Friday at all... but interesting tidbit about tonight into early tomorrow in there...

@high risk @Kmlwx @Eskimo Joe

           Yeah, shear will be increasing later tonight, but there just isn't any instability to get a decent updraft.   Even west of the Blue Ridge where "instability will be surging north", sfc-based CAPE values by early morning will be only a couple hundred J/kg at best.

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4 hours ago, Eskimo Joe said:

Sterling seems pretty bullish about tomorrow. Curious as to what they are seeing to make them so.

      I mean, it's not to going to be a day that we all talk about for years, but in a very tame severe weather season, it has the potential to be one of the better days so far.    Looks like sfc-based CAPE in the 1500 range with modest shear, and if you throw out the anemic NAM nest solutions, most CAMs do bring storms into the area later tomorrow afternoon into an environment that will support some wind reports and maybe an isolated brief TOR.

      For now, I'm less excited about Friday due to downsloping, but the inverted-V soundings do support wind potential if storms can organize.

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Today's SPC morning outlook disco 

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1259 AM CDT Thu Jun 03 2021

   Valid 031200Z - 041200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   THE MID ATLANTIC AND NORTHEAST...

   ...SUMMARY...
   Strong to severe storms are possible across parts of the Mid
   Atlantic and Northeast, mainly this afternoon and evening. Damaging
   wind gusts are expected to be the primary threat, though isolated
   hail and a tornado or two will also be possible.

   ...Synopsis...
   A positively tilted upper trough extending from the Great Lakes into
   the lower MS Valley this morning is forecast to move slowly eastward
   through the period, as an upper ridge amplifies over the Great Basin
   vicinity. A warm front will move northward through portions of New
   England during the day, while a weak surface trough will move
   eastward from the Ohio Valley into the Appalachians. 

   ...Mid Atlantic into Western New England...
   Scattered clusters of convection are expected through the day along
   and east of the weak surface trough moving out of the Ohio Valley,
   within a plume of moist southwesterly flow ahead of the upper
   trough. The area most likely to see some diurnal heating and at
   least modest destabilization prior to the onset of convection is the
   Mid Atlantic into portions of western New England. In this area,
   MLCAPE potentially exceeding 1000 J/kg in conjunction with effective
   shear of 35-45 kt will favor organized convection by mid afternoon.
   Locally damaging wind is expected to be the primary hazard, given
   the anticipated cluster mode, but some hail cannot be ruled out
   despite generally weak midlevel lapse rates. If any supercells
   (either discrete or cluster-embedded) can be sustained, low-level
   flow/shear will also be sufficient to support a tornado or two.

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The last couple of frames of the visible satellite leaves some room for optimism for those of us in the slight risk area. The 12z RAOB from Sterling indicated a convective temp of 79° and we're starting to see a few 80°+ values pop up. If we can get into the lows 80s then perhaps things can work out better for us.

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1 minute ago, Eskimo Joe said:

The last couple of frames of the visible satellite leaves some room for optimism for those of us in the slight risk area. The 12z RAOB from Sterling indicated a convective temp of 79° and we're starting to see a few 80°+ values pop up. If we can get into the lows 80s then perhaps things can work out better for us.

IAD is currently at 82/67.

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2 minutes ago, Eskimo Joe said:

The last couple of frames of the visible satellite leaves some room for optimism for those of us in the slight risk area. The 12z RAOB from Sterling indicated a convective temp of 79° and we're starting to see a few 80°+ values pop up. If we can get into the lows 80s then perhaps things can work out better for us.

Everything south of I-70 looks to be at least 80 by now.  I don't suspect we'll have much problem with bouyancy.  HRRR has liked that I-70 line for several runs now so maybe a thermal boundary setting up there that we'll see some additional focus along

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6 minutes ago, Scuddz said:

Everything south of I-70 looks to be at least 80 by now.  I don't suspect we'll have much problem with bouyancy.  HRRR has liked that I-70 line for several runs now so maybe a thermal boundary setting up there that we'll see some additional focus along

NAM twins putting a decent UHI track in the Frederick/Carroll county tornado zone.

EDIT: HRRR giving some UHI love to Frederick / Carroll / Howard / Baltimore counties.

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The combination of instability and shear seems to be sufficient for a severe box here this afternoon, with the best focus for the those along and north of I-66 in VA and Rt 50 in MD.   As noted by EJ, there is certainly a possibility of a few isolated supercell structures, as indicated by the UH tracks.

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The image below shows how long many hours it takes for a watch box to verify after it's issued. Note the clear correlation between watch probability in the antecedent MCD and number of watch boxes that verify within 2.5 hours of issuance. FWIW, the meso I posted above is 60%.

IMG_20190813_084510.jpg.70b7644627c12c7adfa395311333250d.jpg

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13 minutes ago, mappy said:

I just need rain before 530. thanks. lol 

 

3 minutes ago, H2O said:

anytime before 4:30 here.  but specifically 4:30-5:15  lol

Feel for you guys. I remember wishing these things, when the sports practices/games magically aligned with severe/wet/icy wx over the years. It was especially nice when I occasionally assistant coached...and *I* got to make the cancellation calls (and make them I did).  :) 

Just finished half the lawn...86 IMBY, and kinda soupy w/ DP of 69. Vacillating between full sun and filtered sun through high clouds. Won't be a bit surprised to hear the wx radio squawk within the next 1-2 hours.

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10 minutes ago, vastateofmind said:

 

Feel for you guys. I remember wishing these things, when the sports practices/games magically aligned with severe/wet/icy wx over the years. It was especially nice when I occasionally assistant coached...and *I* got to make the cancellation calls (and make them I did).  :) 

Just finished half the lawn...86 IMBY, and kinda soupy w/ DP of 69. Vacillating between full sun and filtered sun through high clouds. Won't be a bit surprised to hear the wx radio squawk within the next 1-2 hours.

Swim practice for me so all it takes is distant thunder.  Lifeguards love looking at radar apps and listening for rumbles so they can be lazy.

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