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2022 Mid-Atlantic Severe Wx Thread (General Discussion Etc)


Kmlwx
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7 minutes ago, WxWatcher007 said:

Honest to God part of me wants to pack up and head to Ohio to chase…

It's a MDT risk caliber setup if things play out right, but there are lingering uncertainties on details.  The environment near/just south of the front is, well, ridiculous.

You'd be better off trying to get to southern MI/northern IN if possible, given probable arrival prior to sunset.  That area is chaseable. 

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Hmmm from the new Day 2 OTLK at 1730z

Central Appalachians/Mid Atlantic/Carolina Piedmont...
   A cluster(s) of thunderstorms, potentially in the form of an
   organized MCS, may be underway across the central Appalachians at
   the start of the period. Regardless of early storm mode, the
   manifestation of Day 1 convection will be embedded in the modest
   mid-level flow (along with 20-30 kts of deep-layer shear) while
   progressing southeast into a diurnally heated, destabilizing
   airmass. 70+ F surface dewpoints beneath 7+ C/km mid-level lapse
   rates will support 2000-3000 J/kg MLCAPE ahead of the ongoing
   storms. In addition, a mixing boundary-layer will also support
   efficient cold pool production should a more substantial MCS
   materialize, with damaging gusts a concern. A Category 2/Slight Risk
   has been maintained across portions of the Mid Atlantic into the
   Carolinas. Should confidence increase in a more organized, sustained
   MCS becoming established in the morning hours upstream of the
   aforementioned buoyancy, a Category 3/Enhanced risk may be needed.
   Also, some CAM guidance hints at considerable southwestward
   propagation of MCS convection into SC and a southwestward expansion
   of the Slight Risk is also possible in future Day 1 Outlooks.
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16 minutes ago, Hoosier said:

It's a MDT risk caliber setup if things play out right, but there are lingering uncertainties on details.  The environment near/just south of the front is, well, ridiculous.

You'd be better off trying to get to southern MI/northern IN if possible, given probable arrival prior to sunset.  That area is chaseable. 

Ugh, missed opportunity for me. I wouldn’t be able to make it there in time due to work. 

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LWX's thoughts in their afternoon AFD... and they think winds will likely overcome any weakening

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Uncertainty continues to linger with respect to late tonight and
early Tuesday morning with a potential MCS and how far south it will
be able to make it by Tuesday morning. Timing and position of the
activity off to the NW will dictate potential impacts for the area.
If there is a more southern track as seen in some of the CAMs, then
most of the more intense wind/rain would likely miss most of the
area. Whereas, if a northern solution is realized there will likely
be a more widespread/impactful situation to portions of the area.
The latter solution may experience lesser instability as it heads
into the NW area. Do think that regardless of how strong the
reflectivity field looks, winds will likely overcome any weakening.
Guidance has been honing in on a vort track likely through the
middle of the CWA later Tuesday morning. Timing wise, the complex
system may begin to enter portions of the NW areas by 6z and may not
reach the SE areas until 15z. Better MLCAPE will likely be situated
along and west of I-81 with better potential for any
training/isolated flooding threat in the southwest areas. Most
likely hazards will be damaging winds and large hail. This system
has the conditional possibility of producing widespread wind damage
over a large area, should these showers and storms start to bow out
more as they approach the NW areas. The circulation associated with
the MCS may also keep some very heavy rain over an area for an
extended period of time, thus leading to a conditional flooding
threat. Also with the low-level wind field being perpendicular to
the mean flow, an isolated quick spinup is possible. One thing that
could potentially impact the timing and intensity of the environment
could be any potential showers/t-storms ahead of the complex later
today and into the early overnight hours.
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SPC went MOD risk... mentions intense bow echo and derecho potential in 20z disco

 ...20Z Update...
   Portions of the Ohio Valley have been upgraded to a Moderate Risk
   for the anticipation of a highly organized MCS/possible Derecho
   developing from a supercell structure across southern WI. Despite
   the lack of agreement in high-resolution guidance, this supercell is
   traversing a strong buoyancy gradient (with extreme MLCAPE values
   exceeding 5000 J/kg noted in the OH Valley). In addition, 40+ kts of
   effective bulk shear are also present along the buoyancy gradient,
   which expands across a long west-east corridor over northern
   portions of the OH Valley. Expectations are for this supercell
   (which already shows an intense RFD surge per latest KMKX radar
   data) to eventually become more outflow dominant, generating a
   strong cold pool preceded by the extreme instability. Upscale growth
   with the cold pool would support an expanding MCS traversing a
   CAPE/shear parameter space typically associated with bow
   echoes/derechoes. In addition, multicells continue to percolate
   across central IN amid an extremely unstable environment (i.e. 5000+
   J/kg MLCAPE per 18Z mesoanalysis) and an appreciable severe wind
   threat could develop with this cluster as well should upscale growth
   occur.
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Nice writeup from Mount Holly in their afternoon AFD on the model discrepancies and the most likely outcomes given the synoptics.. 

Quiet and humid conditions on tap for most of the night. All eyes then shift on an MCS that will develop over the Great Lakes region and take a run at the Northeast and Mid-Atlantic Tuesday morning. The bulk of the instability will be south of that front over Delmarva, the Delaware Valley, including Philadelphia, and extreme southern New Jersey. With surface dew points well in the 60s to around 70, surface-based CAPE values should be upwards of 1500+ J/kg. The concern is that there is still a good deal of discrepancies among the models as to the timing and placement of the MCS. The 12Z/13 NAM brings a fairly intense squall line into Philadelphia, northern Delmarva, and into southern New Jersey late Tuesday morning and into midday. The 12Z/13 NAMNEST is a bit weaker, but is a bit more to the southwest compared to the NAM, and the brunt of the line would go through eastern Maryland and Delaware before moving into southern New Jersey. Think the NAMNEST would be more probable than the NAM as the instability looks to be limited north of Delaware. The 12Z/13 HRRR seems to follow the NAMNEST, though may be an hour or so slower. The 12Z/13 Fv3 is faster than both the NAM and the HRRR, and brings showers and thunderstorms into Maryland and Delaware in the pre-dawn hours just ahead of the main MCS. Should this happen, this may stabilize the air mass just before the MCS gets there, and the impacts may be more limited compared to the more aggressive NAM/HRRR. 12Z/13 GFS follows suit with a weaker and faster system. 12Z/13 WRF-ARW has the system decaying as it moves into Delmarva late Tuesday morning. 12Z/13 RGEM keeps it together, but is so far south and west that it only impacts the eastern shores of Maryland. The 12Z/13 ECMWF seems to be much slower, not really making it into the southwest portions of the forecast area until midday or so. Feel the best way to handle this is to have the MCS approach Reading just after daybreak Tuesday, and tracking to the south along the stationary front and towards the area of highest instability, which is over Delmarva. Factoring in that these systems also tend to take a right turn, think the strongest portions of the MCS will stay southwest of a line from Reading to Philadelphia to Atlantic City. Will focus an area of likely PoPs on portions of the Delaware Valley, Delmarva, and southwest New Jersey. Heavy rain, strong, damaging winds, and large hail are likely. Although this system should move quickly, there is the potential for localized flash flooding

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20 minutes ago, yoda said:

SPC went MOD risk... mentions intense bow echo and derecho potential in 20z disco

 ...20Z Update...
   Portions of the Ohio Valley have been upgraded to a Moderate Risk
   for the anticipation of a highly organized MCS/possible Derecho
   developing from a supercell structure across southern WI. Despite
   the lack of agreement in high-resolution guidance, this supercell is
   traversing a strong buoyancy gradient (with extreme MLCAPE values
   exceeding 5000 J/kg noted in the OH Valley). In addition, 40+ kts of
   effective bulk shear are also present along the buoyancy gradient,
   which expands across a long west-east corridor over northern
   portions of the OH Valley. Expectations are for this supercell
   (which already shows an intense RFD surge per latest KMKX radar
   data) to eventually become more outflow dominant, generating a
   strong cold pool preceded by the extreme instability. Upscale growth
   with the cold pool would support an expanding MCS traversing a
   CAPE/shear parameter space typically associated with bow
   echoes/derechoes. In addition, multicells continue to percolate
   across central IN amid an extremely unstable environment (i.e. 5000+
   J/kg MLCAPE per 18Z mesoanalysis) and an appreciable severe wind
   threat could develop with this cluster as well should upscale growth
   occur.

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2 minutes ago, Maestrobjwa said:

Yeah that would sound about right, lol Am I imagining it or does south and west (and south east) of here see more severe activity than say...central MD?

Areas south are generally more favored to be warmer/more humid simply by being farther south. Humidity and heat are pretty crucial ingredients for severe weather and storms in general. Though every event is different - the climo for storms is higher south. 

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While we wait

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
631 PM EDT Mon Jun 13 2022

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  West central Montgomery County in central Maryland...
  South central Frederick County in north central Maryland...
  Northeastern Loudoun County in northern Virginia...

* Until 715 PM EDT.

* At 631 PM EDT, a severe thunderstorm was located near Poolesville,
  moving southeast at 20 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Germantown, Lansdowne, Poolesville, Boyds, Belmont, Barnesville,
  Dickerson, Beallsville, Tuscarora and Lucketts.
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1 hour ago, Kmlwx said:

Cappucci thinks it misses Maryland to the south and west it seems. 

Given the position and amplitude of the upper ridge( and the upper low to the NE), I am leaning towards this idea, although DC and parts of S MD might be in the path. Overall trends in the guidance support this. I would be good with a half inch of rain here, hold the drama. I think for my yard the best chance for some decent convection might come from forcing out in front of the main complex with good instability in place.

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So the main show is the stuff coming off Lake Michigan?  Where is that complex in Ohio going?  Sorry have craptacular cell service at a swim meet and can’t access the models or radar ATT.  Though I keep getting alerts that lightening is 14-17 miles and closing.  In fort hunt, va.

Appetizer? Toast here at this swim meet in the next hour? Frickin miserable 

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16 minutes ago, GATECH said:

So the main show is the stuff coming off Lake Michigan?  Where is that complex in Ohio going?  Sorry have craptacular cell service at a swim meet and can’t access the models or radar ATT.  Though I keep getting alerts that lightening is 14-17 miles and closing.  In fort hunt, va.

Appetizer? Toast here at this swim meet in the next hour? Frickin miserable 

Yeah, we are looking at Chicago and north.

 

edit - speaking of which, damn!

 

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34 minutes ago, Eskimo Joe said:

Pretty clear surface boundary pushed along I-270 from that warned cell in Montgomery.

One pushed westward from that smaller cell which went through Carroll county as well. 

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