Rainshadow Posted September 3, 2020 Report Share Posted September 3, 2020 ...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. Quote Link to comment Share on other sites More sharing options...
Rainshadow Posted September 3, 2020 Author Report Share Posted September 3, 2020 This time of year, I think back to my yewth. This was (not close, but still) within walking distance of our house. Quote Link to comment Share on other sites More sharing options...
Parsley Posted September 3, 2020 Report Share Posted September 3, 2020 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. 2 Quote Link to comment Share on other sites More sharing options...
tombo82685 Posted September 3, 2020 Report Share Posted September 3, 2020 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 4 Quote Link to comment Share on other sites More sharing options...
tombo82685 Posted September 3, 2020 Report Share Posted September 3, 2020 Greatest risk IMo is south of white line Quote Link to comment Share on other sites More sharing options...
Rainshadow Posted September 3, 2020 Author Report Share Posted September 3, 2020 59 minutes ago, tombo82685 said: Greatest risk IMo is south of white line Yup, you can see where the combination of shear and instability is greatest at the moment: Quote Link to comment Share on other sites More sharing options...
mshaffer526 Posted September 3, 2020 Report Share Posted September 3, 2020 Is this supposed to intensify as it moves east? Radar doesn't look that impressive. Quote Link to comment Share on other sites More sharing options...
Rainshadow Posted September 3, 2020 Author Report Share Posted September 3, 2020 1 minute ago, mshaffer526 said: Is this supposed to intensify as it moves east? Radar doesn't look that impressive. The best overlapping of shear and instability comes late toward evening/sunset. 1 Quote Link to comment Share on other sites More sharing options...
jmister Posted September 3, 2020 Report Share Posted September 3, 2020 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 south-southeasterly. 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... ATTN...WFO...PHI...AKQ...CTP...LWX...RNK...PBZ...RLX... LAT...LON 38357996 39487908 40307746 40087507 39237465 38407489 37397533 37107609 37187742 37677938 38357996 Edit: Just beaten out by gravitywave! 1 Quote Link to comment Share on other sites More sharing options...
jmister Posted September 3, 2020 Report Share Posted September 3, 2020 Closer look at the SPC's 1630 outlook Tornado (2%, 5%, 10%) 3 Quote Link to comment Share on other sites More sharing options...
Allsnow Posted September 3, 2020 Report Share Posted September 3, 2020 2 hours ago, tombo82685 said: You’re welcome 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 Quote Link to comment Share on other sites More sharing options...
Allsnow Posted September 3, 2020 Report Share Posted September 3, 2020 1 Quote Link to comment Share on other sites More sharing options...
Rainshadow Posted September 3, 2020 Author Report Share Posted September 3, 2020 12 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 Euro has been too wet since 2019. 2 Quote Link to comment Share on other sites More sharing options...
Allsnow Posted September 3, 2020 Report Share Posted September 3, 2020 2 minutes ago, Rainshadow5.8 said: The Euro has been too wet since 2019. Lolz Quote Link to comment Share on other sites More sharing options...
greg ralls Posted September 3, 2020 Report Share Posted September 3, 2020 My wife just left Collegeville, Pennsylvania to drive to Arlington, Virginia after 3:30 PM so I'm hoping she can stay ahead of the storms. Quote Link to comment Share on other sites More sharing options...
Chubbs Posted September 3, 2020 Report Share Posted September 3, 2020 33 minutes ago, greg ralls said: My wife just left Collegeville, Pennsylvania to drive to Arlington, Virginia after 3:30 PM so I'm hoping she can stay ahead of the storms. Storm chase? edit: wish her well of course. 1 Quote Link to comment Share on other sites More sharing options...
mshaffer526 Posted September 3, 2020 Report Share Posted September 3, 2020 First warning up just west of Baltimore. Nasty hook. Quote Link to comment Share on other sites More sharing options...
mshaffer526 Posted September 3, 2020 Report Share Posted September 3, 2020 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. Quote Link to comment Share on other sites More sharing options...
cbelke Posted September 3, 2020 Report Share Posted September 3, 2020 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. Quote Link to comment Share on other sites More sharing options...
cbelke Posted September 3, 2020 Report Share Posted September 3, 2020 Tornado Watch seems further North since earlier predictions, now includes Bucks, MontCo, and Lehigh area. What changed to move it North? Quote Link to comment Share on other sites More sharing options...
tombo82685 Posted September 3, 2020 Report Share Posted September 3, 2020 Sell on anything tornado north of gap-kop-vay Line. Main risk is generally south of city 3 Quote Link to comment Share on other sites More sharing options...
iceman56 Posted September 3, 2020 Report Share Posted September 3, 2020 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... 1 Quote Link to comment Share on other sites More sharing options...
susqushawn Posted September 3, 2020 Report Share Posted September 3, 2020 42 minutes ago, mshaffer526 said: First warning up just west of Baltimore. Nasty hook. this storm still looks to be going strong, nasty right turner Quote Link to comment Share on other sites More sharing options...
cbelke Posted September 3, 2020 Report Share Posted September 3, 2020 Huh, son of a gun... Its raining. Quote Link to comment Share on other sites More sharing options...
susqushawn Posted September 3, 2020 Report Share Posted September 3, 2020 2 hours ago, mshaffer526 said: Is this supposed to intensify as it moves east? Radar doesn't look that impressive. that line to your west is starting to perk up a bit Quote Link to comment Share on other sites More sharing options...
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