2023 Mid-Atlantic Severe Wx Thread (General Discussion)

[Kmlwx]

12z CIPS run roundup - 

At the 84hr timeslot, on the domain/sector that is most aligned with our area, most analogs don't have much for our area. Last analog #15 is June 1/2, 2012. If you use the box that is still relevant to us but a little further west, that June 1/2, 2012 analog goes to #12. A few analogs on there as well that got us some severe. 

Hour 108 has July 23, 2008 (will have to look that up) and a bunch of more toned down events. Interestingly - there's a few analogs that were seemingly minor events but centered on or near the Mid-Atlantic. 

[yoda]

7 minutes ago, Kmlwx said:

12z CIPS run roundup - 

At the 84hr timeslot, on the domain/sector that is most aligned with our area, most analogs don't have much for our area. Last analog #15 is June 1/2, 2012. If you use the box that is still relevant to us but a little further west, that June 1/2, 2012 analog goes to #12. A few analogs on there as well that got us some severe. 

Hour 108 has July 23, 2008 (will have to look that up) and a bunch of more toned down events. Interestingly - there's a few analogs that were seemingly minor events but centered on or near the Mid-Atlantic. 

https://www.spc.noaa.gov/exper/archive/event.php?date=20080723

[yoda]

Some impressive soundings from the 00z NAM tonight across the region... some big hail markers too for Monday's threat on the SARS

[yoda]

00z GFS still has a pretty impressive sim radar at 00z for the region

 

 

[George BM]

I'm actually mildly surprised that they put us in a MRGL for Day 3 as I personally don't see any glaringly obvious signs of models decisively backing off on Mondays potential yet (still better than usual MLLRs leading to sufficient CAPE w/ at least modest deep-layer shear). We'll see what transpires with CAMs and future SPC outlooks.

[Kmlwx]

15 minutes ago, George BM said:

I'm actually mildly surprised that they put us in a MRGL for Day 3 as I personally don't see any glaringly obvious signs of models decisively backing off on Mondays potential yet (still better than usual MLLRs leading to sufficient CAPE w/ at least modest deep-layer shear). We'll see what transpires with CAMs and future SPC outlooks.

From a superstitious weenie standpoint...I'll take it. Last thing we need is a D3 slight or enhanced going to crap. 

[high risk]

3 hours ago, George BM said:

I'm actually mildly surprised that they put us in a MRGL for Day 3 as I personally don't see any glaringly obvious signs of models decisively backing off on Mondays potential yet (still better than usual MLLRs leading to sufficient CAPE w/ at least modest deep-layer shear). We'll see what transpires with CAMs and future SPC outlooks.

    I was surprised too.     The 12z NAM Nest and HiResW FV3 definitely make the case for at least a SLGT.    The CAPE is big-time Monday afternoon, timing of the forcing is ideal, and shear is decent, with even some modest low-level shear.    Verbatim, the NAM Nest is a "south of I-70 show", while the FV3 lets northern areas get in on the show too.

[Kmlwx]

12z NAM (12km) has some beefy soundings in the area for Monday. Timing (at least for now) looks good - I'm onboard (for now)

[Kmlwx]

Here's a screenshot of part of the wind profile from a 12z NAM nest sounding for Monday afternoon - SRH has increased on modeling too it seems. 

[Eskimo Joe]

Based off the morning data, Monday appears to have solid Slight Risk potential. 

[Kmlwx]

5 minutes ago, Eskimo Joe said:

Based off the morning data, Monday appears to have solid Slight Risk potential. 

Unfortunately these days it feels like marginal is the new general thunder, slight is the new SEE TEXT and so forth. I honestly think we will see even fewer moderate risk days in our region with the introduction of the enhanced category. 

[Kmlwx]

Look at this from the 6z Euro for 3z on Monday evening. 

[csnavywx]

30 minutes ago, Kmlwx said:

Look at this from the 6z Euro for 3z on Monday evening. 

Yep. My favorite theta-e delta method (diff of average boundary layer theta-e and average minimum mid-level theta-e) is sitting around 30-35 deg. K on the 3km NAM. My typical threshold for summer severe is 25 or slightly less on global models along with 35-40kt of wind somewhere in the 700-500mb layer to provide adequate shear. In this case, we've got that and some directional shear. I'm still a bit wary convective debris from overnight activity here but if there's no big organized, long lived MCS upstream, then what cloudiness there is might actually help tamp down BL mixing a bit in the late morning hours. Leaning towards ENH being necessary here without major changes.

[Eskimo Joe]

4 hours ago, Kmlwx said:

From a superstitious weenie standpoint...I'll take it. Last thing we need is a D3 slight or enhanced going to crap. 

D2 MOD is the eternal kiss of death.

50 minutes ago, Kmlwx said:

Look at this from the 6z Euro for 3z on Monday evening. 

[Kmlwx]

15 minutes ago, csnavywx said:

Yep. My favorite theta-e delta method (diff of average boundary layer theta-e and average minimum mid-level theta-e) is sitting around 30-35 deg. K on the 3km NAM. My typical threshold for summer severe is 25 or slightly less on global models along with 35-40kt of wind somewhere in the 700-500mb layer to provide adequate shear. In this case, we've got that and some directional shear. I'm still a bit wary convective debris from overnight activity here but if there's no big organized, long lived MCS upstream, then what cloudiness there is might actually help tamp down BL mixing a bit in the late morning hours. Leaning towards ENH being necessary here without major changes.

"We take"

"Tasty"

"  "

 

[yoda]

Afternoon AFD from LWX 

Confidence continues to increase for severe weather Monday
especially for areas near/east of the Interstate 81 corridor.
12z deterministic and ensemble guidance continues to show
continuity in the timing and strength of the deepening/digging
trough over the Great Lakes region and it`s associated cold
front set to cross the region late Monday night into Tuesday
morning. Both the deterministic and ensemble guidance continue
to show a bit of a negative tilt to the trough as it sinks south
into central Appalachians region. This will shift the best
height falls and forcing along and ahead of the cold front as it
pushes across the area Monday afternoon. Instability will be
ample ahead of the boundary with ensemble mean CAPE around
1500-2500 j/kg per the latest 12z guidance. Bulk effective 0-6km
shear values will also be on the order of 25-40 kts with mid-
level lapse rates around 7-8 c/km during the peak heating
period. This will further updraft growth along with organized
and fairly linear activity compared to singular storms or
complexes ahead of the boundary as it passes through. For that
reason, the Storm Prediction Center currently highlights all
areas east of the Alleghenies in a Marginal risk for severe
thunderstorms.

Flooding concerns will remain limited, but non-zero even with D1
and D2 drought antecedent conditions. The high precipitable
water airmass (>1.25-1.50 inches) coupled with strongly forced
convection should yield some opportunity for flooding,
especially in urbanized areas. As a result, the Weather
Prediction Center has painted a Slight risk for flooding over
this area.

[yoda]

3 hours ago, Kmlwx said:

12z NAM (12km) has some beefy soundings in the area for Monday. Timing (at least for now) looks good - I'm onboard (for now)

Some quite large hail markers on the SARS as well on the 12z NAM soundings on COD

[yoda]

Oh (NW Prince William County)

 

[yoda]

12z NAM Nest also has some pretty decent UD Helicity Swaths between i66 and i70 Monday evening

[Eskimo Joe]

If we wake up Monday with little or no debris clouds, it could be interesting. Stout mid level lapse rates are a key ingredient in overcoming the mesoscale geographic features that mitigate a lot of our severe weather days.

[yoda]

Mark likes Monday still - @Ellinwood

 

 

[CAPE]

Day 3 Convective Outlook AMEND 1
   NWS Storm Prediction Center Norman OK
   0312 PM CDT Sat Jun 24 2023

   Valid 261200Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR THE
   MID-ATLANTIC STATES AND CAROLINAS...

   AMENDED FOR EXPANSION/UPGRADING OF SEVERE PROBABILITIES IN THE
   MID-ATLANTIC AND SOUTHEAST

   ...SUMMARY...
   A severe threat is expected to develop on Monday from the Carolinas
   into the Mid-Atlantic, where damaging winds and hail will be
   possible. An isolated severe threat will also be possible in the
   northern High Plains.

   ...Amended discussion for the Eastern U.S....
   A mid to upper-level low will meander slowly eastward over the
   central Great Lakes during the period.  An associated trough
   initially over the OH Valley/southern Appalachians is forecast to
   gradually shift eastward into the central Appalachians/Carolinas.  A
   belt of moderate southwesterly 500-mb flow (25-40 kt) will
   overspread a destabilizing warm sector ahead of a front/composite
   outflow over the Appalachians.  Strong heating ahead of the front
   and very moist low levels (66-74 deg F surface dewpoints) will
   likely result in a moderate to very unstable airmass from the
   Southeast northward into the Mid-Atlantic states.  Several linear
   clusters of intensifying thunderstorms are forecast to develop by
   early afternoon in the immediate lee of the higher terrain.  Further
   upscale growth into a more expansive band of linear segments is
   expected by late afternoon/early evening from the Mid-Atlantic
   states southward into the Carolinas.  Damaging gusts appear to be
   the primary hazard due to 50-70 mph gusts.  Isolated large hail may
   accompany the stronger cores.  

[yoda]

Quite an expansion on the updated Day 3 of the SLGT risk

[Eskimo Joe]

If things sustain or uptick a bit I could eventually see a D1 ENH for southern Delmarva or RIC land. Really not confident about this north of I-66 until I wake up Monday morning and see we aren't contaminated with debris clouds or something else.

[87storms]

33 minutes ago, Eskimo Joe said:

If things sustain or uptick a bit I could eventually see a D1 ENH for southern Delmarva or RIC land. Really not confident about this north of I-66 until I wake up Monday morning and see we aren't contaminated with debris clouds or something else.

I'd like to see things form west of or around i81 instead of relying on something forming right overhead just east of the mountains.  I'd feel more confident about organized cells for i95 east, but we shall see.  With dews forecasted to be 70+, there's gonna be some legitimate downpours for those who score.

[yoda]

00z HRRR at range of course, but that's pretty nice looking radar forecast from hours 43-48

Wouldn't mind the 00z NAM NEST or the 00z FV3 either

[MN Transplant]

1 hour ago, yoda said:

00z HRRR at range of course, but that's pretty nice looking radar forecast from hours 43-48

Wouldn't mind the 00z NAM NEST or the 00z FV3 either

00z NAM Nest looks good for severe.  Always an IMBY game though.

[Kmlwx]

Liking the looks of many of the CAMs - but they are all still at range. Will be interesting to see how the modeling trends tomorrow. 

[high risk]

1 hour ago, Kmlwx said:

Liking the looks of many of the CAMs - but they are all still at range. Will be interesting to see how the modeling trends tomorrow. 

      Definitely an overall very interesting 00Z suite.     While there are still some valid questions about debris from Sunday convection and how the Monday storms evolve. I would think that much of the area wakes up tomorrow in a Day 2 SLGT.    

edit:   I totally missed SPC updating the Day 3 to put us in a SLGT, so this post was pretty useless.   I guess it's possible that parts of the area could get a Day 2 ENH, but the question marks listed might preclude that for now.

[yoda]

Good morning hatched hail