2020 Mid-Atlantic Severe Weather - General Thread

[MN Transplant]

8 hours ago, yoda said:

00z NAM and 3km NAM sim radar look interesting around 03z/04z MON... I guess some sort of an MCS?

Both 00z WRF-ARW and 00z WRF-ARW2 keep majority of storms down by EZF

00z WRF-NMM looks more like the NAM twins but is an hour or 2 faster

00z HRDRPS looks fun DC south

One thing that we seem to have going for us is that the NAM and HRRRs don't show a lot of impact from the mid-day remnants of the precip that is in WV/OH right now.  A couple hundreths of an inch of rain and it rebounds to the upper 70s after.  If that happens, we have a better chance as far north as DC.  But, I'd still rather be between EZF and RIC.

[osfan24]

Threat has shifted way far south in the past 24 hours. Gone from Central MD to south of DC.

[snowfan]

6 minutes ago, osfan24 said:

Threat has shifted way far south in the past 24 hours. Gone from Central MD to south of DC.

Shrug. Latest HRRR and both 12z NAMs bring showers/storm thru DC tonight. The threat for severe anywhere near was never that strong anyway.

[yoda]

LWX afternoon AFD seems to be suggesting that the front didnt get as far south as they thought it would... so places up by DC may be in the game this evening for a severe storm 

.NEAR TERM /THROUGH TONIGHT/...
The general theme for the first half of this system is on track,
as the showers associated with the lead shortwave trough are
exiting southern Maryland. In its wake, there are some breaks in
the clouds. In addition, the surface boundary has been slower to
drop southward, with southerly winds observed to approximately
I-68/I-70. So while the clouds and showers initially seemed to
suggest the best convective threat may shift to the south, the
southerly flow is helping to build a bit of instability ahead of
the next shortwave trough which will arrive this evening.

Severe threat: Initial thinking based on 12Z guidance and
earlier satellite trends was that the best threat of a stronger
thunderstorm which may producing locally damaging winds would be
mainly over the central Virginia piedmont to perhaps southern
Maryland. However, unless the surface boundary quickly surges
southward, there may be enough instability for a threat a little
farther north. With that said, the next round of forcing won`t
be arriving until this evening. So while shear will be
sufficient, limited instability and a stabilizing boundary layer
may limit this threat.

Heavy rain threat: Ultimately this could be more of a hydro
event, albeit a marginal/localized one. Most guidance still
suggests widespread coverage of showers and embedded
thunderstorms this evening as the shortwave trough arrives and a
low level jet impinges on the low level boundary with
precipitable water values possibly in excess of 1.5 inches.
A low pressure center could develop that would also enhance
lift. Localized convergence along the boundary could cause
showers/storms before the main batch (like currently seen over
Ohio)...which could heighten the threat along a particular
corridor. A lot of model raw QPF output paints a stripe of 1-2
inches of rain (due to persistent or repetitive showers/storms)
along the US-50/I-66 corridor, intersecting the DC metro. With
fairly moist soils, this could present a flash flood threat.
However, other metrics like precipitation placement potential
and moisture convergence suggests the corridor might be slightly
displaced to the south (where such totals could be handled
better). That, combined with overall uncertainty about the
convective evolution, has precluded the issuance of a Flash
Flood Watch at this time, but will be discussing with the
incoming shift about the potential need for one.

[CAPE]

Mount Holly AFD

Quote

A convective complex should traverse the Delmarva region this evening into the overnight with the northern extent brushing southern to especially central New Jersey. Given the incoming cold front and some sharpening of the upper-level trough to our northwest, showers on the northwest side of any organized convection should extend into the I-95 corridor and perhaps even a bit farther inland. There is the chance some thunderstorms become locally strong to severe across portions of Delmarva with strong winds, however this will highly depend on if convection remains organized and surface- based. If cold pool generation occurs with organized convection, that would increase the chance for strong surface winds.

Yeah because I didn't get enough wind on Thursday. Let the severe stuff sink just south. That's what I expect to be the case.

[Vice-Regent]

7 minutes ago, C.A.P.E. said:

Mount Holly AFD

Yeah because I didn't get enough wind on Thursday. Let the severe stuff sink just south. That's what I expect to be the case.

You actually don't want this? This is an incredible setup that should not be squandered in these parts. These are not really our caliber ... very rare to have the lows pass this close in the Spring. They usually go to our north or west.

[CAPE]

Temp has jumped up to 75 after being in the mid 60s for most of the day.

[CAPE]

Just now, Vice-Regent said:

You actually don't want this? This is an incredible setup that should not be squandered in these parts. These are not really our caliber ... very rare to have the lows pass this close in the Spring. They usually go to our north or west.

I'll take it, just not the wind. Just finished cleaning up twigs and branches and tree debris all over the driveway, yard, deck..

[MN Transplant]

79/63 at DCA.

Hit 77.4 here a bit ago.

[wawarriors4]

Currently 82/67 just NW of Fredericksburg. Hope to see a light show tonight with the lightning, although, the rain amounts could be pretty heavy (1”+) over a few areas. 

[MN Transplant]

Flash flood watch

[osfan24]

27 minutes ago, MN Transplant said:

Flash flood watch

Makes sense. Not seeing any severe risk, and chance of just thunderstorms even seems low looking at radar, but pretty good batch of moisture headed this way.

[CAPE]

Heard some thunder here and heavy rain, but I slept trough it mostly. Picked up 0.87" .

Just guessing, but probably any convection with wind potential was south of here.

[Kmlwx]

Too early to tell - but the 0z CIPS guidance is throwing out some analogs that could be interesting in the 120hr time frame. The event right before June 4, 2008 is showing up

 

ETA: It was May 31, 2008 and that was a moderate risk day for us. Then we all know what happened a few days later...

[yoda]

3 hours ago, Kmlwx said:

Too early to tell - but the 0z CIPS guidance is throwing out some analogs that could be interesting in the 120hr time frame. The event right before June 4, 2008 is showing up

 

ETA: It was May 31, 2008 and that was a moderate risk day for us. Then we all know what happened a few days later...

For those that want to look at the 5/31/2008 event - https://www.spc.noaa.gov/exper/archive/event.php?date=20080531

ETA -- 120 hours would be the weekend, yes?  Saturday or Sunday?  And could you link me to the CIPS severe again?  I lost my link

[Kmlwx]

15 hours ago, yoda said:

For those that want to look at the 5/31/2008 event - https://www.spc.noaa.gov/exper/archive/event.php?date=20080531

ETA -- 120 hours would be the weekend, yes?  Saturday or Sunday?  And could you link me to the CIPS severe again?  I lost my link

0z CIPS guidance has backed off of that run now. 

[high risk]

Fire up the thread - we have a day 3 MRGL!!!!      It's remarkable in May that we've gone two weeks without even the need for a wishcast, and Friday doesn't look all that impressive, but we take what we're given.     There are big timing differences with the front, and instability is not all that exciting, but if we can get storm initiation later Friday, deep layer shear appears to be sufficient for a few cells to reach severe limits.

[Kmlwx]

35 minutes ago, high risk said:

Fire up the thread - we have a day 3 MRGL!!!!      It's remarkable in May that we've gone two weeks without even the need for a wishcast, and Friday doesn't look all that impressive, but we take what we're given.     There are big timing differences with the front, and instability is not all that exciting, but if we can get storm initiation later Friday, deep layer shear appears to be sufficient for a few cells to reach severe limits.

It has been a terribly boring stretch for lovers of exciting weather...I've been bored - luckily have been in the process of moving so other things have been occupying time. Would love a nice event to track. We wait. 

[George BM]

There hasn't been a MOD or HIGH risk issued anywhere in the country this month from SPC. Quiet indeed. 

One time period that I'll watch is following the cool shot at the beginning of next week. As a ridge tries to build in during the week watch for any potential NW-flow event.

Small note: Some of the 0z convective models hint at scattered storms/convection trying to develop tomorrow afternoon from Bertha. There looks like there will be some low-level shear (not super impressive LLshear but some LLshear). If storms can develop tomorrow there might be a risk of gusty winds and perhaps a rotating meso or two. 

#Notanexpertopinion

[Eskimo Joe]

2 hours ago, high risk said:

Fire up the thread - we have a day 3 MRGL!!!!      It's remarkable in May that we've gone two weeks without even the need for a wishcast, and Friday doesn't look all that impressive, but we take what we're given.     There are big timing differences with the front, and instability is not all that exciting, but if we can get storm initiation later Friday, deep layer shear appears to be sufficient for a few cells to reach severe limits.

Friday reeks of scattered wet microburst, warn-on-4-red-pixels storms.

[high risk]

24 minutes ago, Eskimo Joe said:

Friday reeks of scattered wet microburst, warn-on-4-red-pixels storms.

     

That would still be the best SVR day we've had all month, and it ain't even close.

[Kmlwx]

Hope June gets more exciting. I don't need days, on days of severe - but a nice line or something area-wide would be nice. Even just a good lightning show at this point. Talk about a snoozefest. 

[dailylurker]

Just now, Kmlwx said:

Hope June gets more exciting. I don't need days, on days of severe - but a nice line or something area-wide would be nice. Even just a good lightning show at this point. Talk about a snoozefest. 

I think i heard thunder once and it's almost June.

[Kmlwx]

10 minutes ago, dailylurker said:

I think i heard thunder once and it's almost June.

I think we had better severe in February than May

[high risk]

4 hours ago, George BM said:

Small note: Some of the 0z convective models hint at scattered storms/convection trying to develop tomorrow afternoon from Bertha. There looks like there will be some low-level shear (not super impressive LLshear but some LLshear). If storms can develop tomorrow there might be a risk of gusty winds and perhaps a rotating meso or two. 

#Notanexpertopinion

 

       The 12z HRRR shows this scenario.    It has low-topped convection moving from south to north, in an environment with some instability and good low-level directional shear.    The HRRR is more favorable than other CAMs in terms of instability and shear (which is why its reflectivity looks better than most other solutions), so it may be considered a bit of an outlier for now, but it's within the range of possible outcomes.

[yoda]

MRGL risk for Day 1... 2% TOR and 5% wind... for i95 corridor and west

TOR risk is from N VA into C PA on day 1 OTLK

No real disco for our area though besides few short sentences lol

 

SLGT for day 2 for most of LWX CWA... 2% TOR and 15% wind... potential for greater tornado risk stated in disco on day 2 btw... all depends on low level flow and surface wind direction 

[yoda]

For Friday, day 2 morning SPC OTLK 

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1245 AM CDT Thu May 28 2020

   Valid 291200Z - 301200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN
   MID-ATLANTIC INTO THE NORTHEAST STATES...

   ...SUMMARY...
   Severe thunderstorms are possible across portions of the northern
   Mid-Atlantic and Northeast States Friday afternoon through Friday
   evening.

   ...OH Valley into the Northern Mid-Atlantic and Northeast...
   A shortwave trough and attendant vorticity maximum are forecast to
   move from the middle OH Valley northeastward into western portions
   of the Northeast states on Friday. Another shortwave will move
   through the Upper Great Lakes, in close proximity to the lead wave.
   By early Saturday morning, these two shortwaves will have merged
   into one coherent shortwave extending from southern Quebec southward
   into the northern Mid-Atlantic.

   Dewpoints in the upper 60s (possibly low 70s) are anticipated from
   the Mid-Atlantic northward into upstate NY, with slightly lower
   values expected across the middle and upper OH Valley. Given this
   low-level moisture, the air mass will destabilize under modest
   heating ahead of the approaching shortwave troughs and associated
   cold front. Lead shortwave trough is expected to induce convective
   initiation throughout the warm sector over the Northeast and
   northern Mid-Atlantic, while the second shortwave trough and
   attendant cold front aid in convective development over the middle
   and upper OH Valley. 

   A predominately multicell mode with numerous line segments is
   anticipated. Vertical shear is strong enough to support storm
   organization, resulting in the potential for damaging wind gusts
   with the more robust line segments. Some isolated hail is also
   possible, particularly with any more discrete storms. The tornado
   threat will depend largely on direction of the surface winds and
   strength of the low-level flow. A more southerly surface-wind
   direction combined with stronger low-level flow will contribute to
   greater low-level shear and higher tornado potential. Highest
   likelihood for these conditions currently exists from central VA
   northward into upstate NY. However, confidence is occurrence is
   currently low, since most of the guidance either lacks southerly
   surface winds or enhanced low-level flow. Consequently, only
   marginal tornado probabilities will be included with this outlook

[Rhino16]

Thunderstorms approaching Richmond. It was weird, the Thunder didn’t happen until it was really close, or I must have missed one.

[Amped]

Most of the CAM don't have storms in our are until well after 00z.  Not the best time for tornados.  NRN PA and NY get convection earlier in the day, they probably have a better chance.

[Newman]

Updated Day 2 outlook, 15% wind, 15% hail (new to this outlook), 2% tornado.