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2018 Mid-Atlantic General Severe Discussion

Kmlwx

By Kmlwx,
in Mid Atlantic

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yoda

yoda

Posted
Posted
1 hour ago, high risk said:

while you're totally correct that the strongest signal is in the HRRR, the NAM3 does have a system arriving around the same time - it's just not quite as organized or expansive.

04z HRRR still brings in an organized complex through the region from 08z to 12z

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AfewUniversesBelowNormal

AfewUniversesBelowNormal

Posted
Posted

Not really a good pattern for severe weather general. The Atlantic tropical ridge is too strong. We need a Lower Midwest heat ridge, Southwest cutoff Low, or something like the late '90s where it gets really warm like upper 90s to 100 in July, coming from the dusty Upper Midwest. This pattern is tropical. 

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Round Hill WX

Round Hill WX

Posted
Posted
29 minutes ago, George BM said:

Lots of convective models are actually hinting at a thunderstorm cluster affecting at least parts of the sub forum tomorrow afternoon with fairly decent CAPE (especially southwest).

NAM 3K has a MCS surviving overnight into tomorrow. CAPE is decent along and west of the Potomac.

 

nam3km_cape_neus_33.png

nam3km_mslp_pcpn_frzn_neus_32.png

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yoda

yoda

Posted
Posted

STW coming soon for a good part of the region

http://www.spc.noaa.gov/products/md/md0398.html

 

mcd0398.gif

Mesoscale Discussion 0398
   NWS Storm Prediction Center Norman OK
   1256 PM CDT Sun May 13 2018

   Areas affected...portions of southeast OH...northern WV including
   Panhandle...western MD...southwest PA...northwest VA

   Concerning...Severe potential...Watch possible 

   Valid 131756Z - 132000Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Isolated to widely scattered thunderstorms may develop
   this afternoon and move southeast, with a risk for large hail and
   damaging winds.  A tornado or two will also be possible.  A Severe
   Thunderstorm Watch may be needed prior to 20Z/4 pm EDT.

   DISCUSSION...Mesoanalysis at 17Z placed a nearly stationary front
   through central portions of OH and extending east/southeast into far
   northern VA.  Strong diabatic heating of a moist boundary layer
   (lower/mid 60s surface dew points) combined with relatively steep
   mid-level lapse rates will result in pockets of moderate
   surface-based instability by mid afternoon.  Latest visible imagery
   shows deepening cumulus clouds near/south of the front, and
   continued heating combined with weak frontal convergence should
   contribute to isolated thunderstorm development this afternoon. 
   Veering flow in the lowest 1-2 KM becomes largely unidirectional
   within the bulk of the cloud-bearing layer, with deep-layer shear
   ranging between 35-45 kts.

   Initial thunderstorm development may pose a risk for large hail and
   damaging winds.  Slightly more favorable low-level shear near the
   front would suggest at least some risk for a tornado, especially
   within the first few hours of initiation.  With time, a couple of
   small clusters of storms may move southeast with a risk for severe
   hail/wind.

   The area is being monitored for a Severe Thunderstorm Watch, which
   may be needed prior to 20Z.

   ..Bunting/Grams.. 05/13/2018

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...CTP...LWX...PBZ...RLX...
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yoda

yoda

Posted
Posted 
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
238 PM EDT Sun May 13 2018

.SYNOPSIS...
A frontal boundary will remain near the area through much of
next week. Another cold front will then approach from the
northwest late in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface frontal boundary early this afternoon now resides from
near Cumberland MD to Manassas VA and southeastward towards the
Virginia Tidewater. To the northeast of this boundary, cooler
temperatures and low clouds are present. To the southwest, there
exists clearer skies aside from developing a cumulus field.

An interesting setup presents itself this afternoon and evening,
and one that has a conditional but increasing threat of severe
weather. The surface boundary is expected to remain more or less
stationary for the remainder of the day, as a wave of low
pressure moves along the boundary from Ohio this afternoon,
east- southeastward and into central Virginia by late this
evening. In the warm sector, temperatures have already warmed
into the 80s and may perhaps hit 90F again in a few locales.
Surface dew points will maintain readings in the low to mid 60s
as well. In addition, relatively steep mid level lapse rates of
around 7C/KM still exist in this sector. This combination has
already led to 1000-1500 J/KG of MLCAPE. To the northeast of
this boundary, while there is expected to be little to no
surface instability, there`s indication that elevated
instability will move aloft, and MUCAPE values near 1000 J/KG
may exist by late this afternoon and evening. There is ample
wind shear across the region, although the highest values are
displaced northward from the best instability, with 0-6KM values
ranging from 30-40 knots in the warm sector to 50 knots across
Maryland. The earlier uncertainty with regards to the capping
inversion in place is being reduced as SPC Mesoanalysis is
depicting lessening MLCIN across portions of WV, OH, and
southwestern PA. Morning convection over Ohio/PA has likely set
down some outflow boundaries, and those along with the frontal
convergence will likely be enough to spark shower/thunderstorm
development across OH/WV/PA again this afternoon, and spread
eastward into eastern WV/MD/VA. If this does occur, a severe
threat exists, with damaging winds and large hail the main
threats in the warm sector, large hail on the cool side, and
perhaps a low risk of an isolated tornado if a cell can move
along the frontal boundary. Locally heavy rain will also occur.

Convection will wane overnight, with lows from the upper 50s to
low 60s. Areas of fog/mist and low ceilings are likely again on
the cool side of the frontal boundary, which may settle back
southwestward as it did last night to a position from Cumberland
to Charlottesville.
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Eskimo Joe

Eskimo Joe

Posted
Posted
1 minute ago, yoda said:

STW for Fauquier/Culpepper/ hail to golf ball size

Now a TOR:

Quote 

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Baltimore MD/Washington DC
609 PM EDT SUN MAY 13 2018

The National Weather Service in Sterling Virginia has issued a

* Tornado Warning for...
  Central Culpeper County in northern Virginia...

* Until 630 PM EDT.

* At 609 PM EDT, a severe thunderstorm capable of producing a tornado
  was located 7 miles northwest of Culpeper, moving southeast at 20
  mph.

  HAZARD...Tornado.

  SOURCE...Radar indicated rotation.

  IMPACT...For those in the direct path of a tornado touchdown, 
           flying debris will be dangerous to those caught without 
           shelter. Damage to roofs, siding, and windows may occur. 
           Mobile homes may be damaged or destroyed. Tree damage is 
           likely.

* This dangerous storm will be near...
  Culpeper around 625 PM EDT.

 

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mappy

mappy

Posted
Posted
7 hours ago, high risk said:

       The 00Z NAM3 likes 00z Wednesday, with really volatile environment progged for our area.

06z NAM still advertising the same. Nice line dropping south out of PA 21z-00z

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