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9/3 Enhanced Risk Observations


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...Middle Atlantic...

   Latest water-vapor imagery depicts a strong upper trough over
   southwestern MB/eastern ND, digging southeast line with latest model
   guidance. Height falls ahead of this feature should encourage a
   notable short-wave trough over the Mid-South to eject northeast
   before approaching the Middle Atlantic by early afternoon. At
   03/0530z, radar data exhibited a small cluster of thunderstorms
   immediately ahead of the southern short wave near the KY/TN border.
   This activity should advance across the TN Valley into WV early in
   the period before appreciable surface heating enhances buoyancy
   downstream. It appears the greatest corridor of steep low-level
   lapse rates should be in the lee of the central Appalachians from VA
   into southern NJ where temperatures should rise into the upper
   80s-90F. 00z NAM suggests a 50kt 500mb speed max will translate
   across WV by 18z, then off the NJ coast by 04/00z.

   Latest thinking is scattered deep convection should begin to
   intensify ahead of the short wave by late morning across the higher
   terrain of the central Appalachians, then spread/develop east toward
   the Delmarva within a plume of high-PW air (2+ inches). While
   mid-level lapse rates will necessarily be modest due to the abundant
   PW, robust updrafts are expected given the shear/buoyancy. Forecast
   soundings suggest discrete supercells are possible and latest CAMs
   support this scenario. Earlier thoughts regarding the prospect for a
   corridor of enhanced robust convection continue. While a few
   tornadoes are certainly possible, the primary threat should be
   damaging winds, especially if bow-type structures ultimately evolve.




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Quick glance at latest models.....NAM leaning northern and central areas, RGEM/HRDPS leaning central and especially southern parts of our region. Latest HRRRR, sort of the canadian's side (along with SPC).

Current convection is where it's supposed to be based on radar....we'll see how things go this afternoon.





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18 hours ago, tombo82685 said:

I could possibly see that enhanced getting bumped north a bit tomorrow if we see area of low pressure track a bit further north. Plenty of shear to work with and if we get prolonged sunshine it should get the instability going. Not seeing really any EML, so this will be instability and shear driven

You’re welcome 


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   Mesoscale Discussion 1673
   NWS Storm Prediction Center Norman OK
   0206 PM CDT Thu Sep 03 2020

   Areas affected...the Mid-Atlantic

   Concerning...Severe potential...Tornado Watch likely 

   Valid 031906Z - 032100Z

   Probability of Watch Issuance...95 percent

   SUMMARY...A tornado watch will be needed this afternoon as a
   damaging wind and tornado threat increases.

   DISCUSSION...A broad area of shower activity extends from the Ohio
   Valley into Pennsylvania and New York amid a belt of strong
   mid-level flow. Areas south and east of this activity have slowly
   destabilized through the day with temperatures now in the upper 80s
   to low 90s in northern Virginia, eastern Maryland, and Delaware. In
   addition, the boundary layer is very moist with dewpoints in the mid
   to upper 70s. This has yielded moderate MLCAPE ranging from 1000 to
   2000 J/kg across the region despite very weak mid-level lapse rates
   (5 C/km per 18Z IAD RAOB). Expect at least a few strong storms to
   develop in the eastern periphery of the cloud shield in the next 1-2
   hours as destabilization continues and deep-layer ascent increases
   ahead of a shortwave moving out of West Virginia. 

   Once storms develop, they will likely become supercellular, at least
   initially, given 40-45 kts of effective shear (per KLWX VWP and 18Z
   IAD RAOB). 18Z IAD RAOB showed relatively weak flow in the lowest
   1.5 km, but upstream VWP from KRLX shows strong (40 kt) flow at 1km.
   Once this overspreads northern Virginia, Maryland, and Pennsylvania
   in a few hours, the damaging wind threat will increase and low-level
   shear will increase which should increase the tornado threat. The
   best tornado threat will likely be across northern Virginia,
   southern Maryland, and far southern Pennsylvania where there has
   been less mixing and surface winds remain southerly or

   A tornado watch will likely be needed in the next hour or two as
   storm coverage/intensity increases.

   ..Bentley/Grams.. 09/03/2020

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


   LAT...LON   38357996 39487908 40307746 40087507 39237465 38407489
               37397533 37107609 37187742 37677938 38357996 


Edit: Just beaten out by gravitywave!

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3 minutes ago, mshaffer526 said:

Not sure if that stuff in Maryland is going to move far enough north. Good sized gap between the cells in the Susquehanna Valley and what's down there. 



Yup, could be right down the ol' uprights for a lot of us unless that fills in. Been cloudy the last few hours so not seeing much sun to destabilize the environment right now.

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52 minutes ago, Allsnow said:

The euro has been too wet since Saturday for our area. Since Sunday I have only had .04 which is way under what the euro was forecasting 

The annoying thing is it rains just enough to keep things damp every day and with the high dews things never dry out to do stuff that needs it dry.   Same thing today, an off and on crappy drizzle.   Just rain and get it over with...

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