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E PA/NJ/DE Spring 2018 OBS Thread

Rtd208

By Rtd208,
in Philadelphia Region

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The Iceman

The Iceman

Posted
Posted

Really liking the severe threat today for most of the area. Should have ml cape in the 2-3000 range, and enough shear in place for things to go off. 3km nam and other mesos bring a vicious squall/derecho between 22-23z. Damaging winds are the main threat but i wouldn't rule out a tornado or two. Thermodynamics are going to be off the chart for this area. The best combo of thermos and shear though is the lehigh valley. That would be my target zone for tornadoes though I don't think they are likely. I also don't see these cells dying after sunset...this line will go straight to the coast imo.

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The Iceman

The Iceman

Posted
Posted

81F/67 DP here already. With the abundant clearing, no crapvection, and DP's possibly getting into the low 70s in SE PA, I think SPC may go moderate risk in NE PA into SNY and then enhanced risk to the coast including most of the mt holly cwa. This is just my opinion though. Things are going great though for a significant severe day this afternoon.

 

New MD out from SPC:

 

Quote 

 Mesoscale Discussion 0423
   NWS Storm Prediction Center Norman OK
   1043 AM CDT Tue May 15 2018

   Areas affected...Central and northern Pennsylvania into southern New
   York and southwest New England

   Concerning...Severe potential...Watch likely 

   Valid 151543Z - 151815Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Severe storms are likely to develop over the next several
   hours from central and northern Pennsylvania into southern New York,
   continuing into southern New England by late afternoon. Severe wind
   and hail are likely across all areas, with a few tornadoes possible
   mainly from northeast Pennsylvania into southern New England. As
   such, one or more severe and/or tornado watches will be needed
   today.

   DISCUSSION...Surface analysis shows a cold front across northwest PA
   into OH, with a pre-frontal trough across central NY into central
   PA. A progressive area of early-day thunderstorms has produced
   outflow across much of southern NY to near the northern PA border.

   Satellite imagery shows strong heating is occurring across the warm
   sector, with a plume of mid to upper 60s F dewpoints spreading north
   across PA and NJ, and likely into southern NY later today. In
   addition, the aforementioned outflow will continue to modify, while
   likely maintaining some degree of enhanced low-level wind shear this
   afternoon.

   Thunderstorms currently exist along the cold front from western PA
   into western NY, and should continue a gradual increase in intensity
   as the air mass destabilizes to the east. In addition to these
   storms, other storms are expected to form near the surface trough,
   and perhaps atop the old outflow boundary. Deep-layer shear will
   favor cellular activity away from the cold front, while a mixed
   storm mode including bows or embedded supercells are possible along
   the front. Strong heating and steep lapse rates aloft will favor
   large hail, with an increasing damaging wind by the time storms
   organize into a line. Any cellular activity will be capable of large
   hail, perhaps very large, along with a few tornadoes where low-level
   shear is maximized.

 

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SmokeEater

SmokeEater

Posted
Posted
81F/67 DP here already. With the abundant clearing, no crapvection, and DP's possibly getting into the low 70s in SE PA, I think SPC may go moderate risk in NE PA into SNY and then enhanced risk to the coast including most of the mt holly cwa. This is just my opinion though. Things are going great though for a significant severe day this afternoon.
 
New MD out from SPC:
 
Mesoscale Discussion 0423  NWS Storm Prediction Center Norman OK  1043 AM CDT Tue May 15 2018  Areas affected...Central and northern Pennsylvania into southern New  York and southwest New England  Concerning...Severe potential...Watch likely   Valid 151543Z - 151815Z  Probability of Watch Issuance...95 percent  SUMMARY...Severe storms are likely to develop over the next several  hours from central and northern Pennsylvania into southern New York,  continuing into southern New England by late afternoon. Severe wind  and hail are likely across all areas, with a few tornadoes possible  mainly from northeast Pennsylvania into southern New England. As  such, one or more severe and/or tornado watches will be needed  today.  DISCUSSION...Surface analysis shows a cold front across northwest PA  into OH, with a pre-frontal trough across central NY into central  PA. A progressive area of early-day thunderstorms has produced  outflow across much of southern NY to near the northern PA border.  Satellite imagery shows strong heating is occurring across the warm  sector, with a plume of mid to upper 60s F dewpoints spreading north  across PA and NJ, and likely into southern NY later today. In  addition, the aforementioned outflow will continue to modify, while  likely maintaining some degree of enhanced low-level wind shear this  afternoon.  Thunderstorms currently exist along the cold front from western PA  into western NY, and should continue a gradual increase in intensity  as the air mass destabilizes to the east. In addition to these  storms, other storms are expected to form near the surface trough,  and perhaps atop the old outflow boundary. Deep-layer shear will  favor cellular activity away from the cold front, while a mixed  storm mode including bows or embedded supercells are possible along  the front. Strong heating and steep lapse rates aloft will favor  large hail, with an increasing damaging wind by the time storms  organize into a line. Any cellular activity will be capable of large  hail, perhaps very large, along with a few tornadoes where low-level  shear is maximized.

 
Good call on the mod, no enhanced down here though.

Sent from my SM-G950U using Tapatalk

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The Iceman

The Iceman

Posted
Posted
3 minutes ago, ChescoPaWxman said:

Currently just 65.5 down in Sea Isle City NJ with the chilly ocean water doing it's thing...while back inland here in NW Chester County PA 82.7 and a dew point of 72. Watch for strong to near severe storms to enter the NW part of East Nantmeal Twp by around 530pm

wow! that is even higher than progged I believe. I think SPC is still a bit cautious on the timing which is why they didn't extend the 30% wind to the coast imo But with dews in the low 70s, I have a hard time seeing that line breaking up even if it comes through after dusk. SPC mentioned the D word again in the latest outlook, they seem pretty gung ho for the northern areas of the CWA, I believe the southern areas will see some good action too though. I'd be more worried about the shear further south but I think we have more than enough for a big wind threat.

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The Iceman

The Iceman

Posted
Posted

Actually looking at the radar, I think I see why SPC didn't extend the enhanced much further south. The MCV is western PA looks to be developing so that the bow will ride right across northern PA west to east along I-80, but below that bow associated with the MCV, will be a training thunderstorm set up. You can kind of see this setting up now in western PA. Those that miss the wind to the north, will be in prime position for training storms/flash flooding.

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BBasile

BBasile

Posted
Posted
4 minutes ago, The Iceman said:

Actually looking at the radar, I think I see why SPC didn't extend the enhanced much further south. The MCV is western PA looks to be developing so that the bow will ride right across northern PA west to east along I-80, but below that bow associated with the MCV, will be a training thunderstorm set up. You can kind of see this setting up now in western PA. Those that miss the wind to the north, will be in prime position for training storms/flash flooding.

Yes, this is pretty much what the NAM shows.  The higher risk areas have better shear and better instability as well, even though SBCAPE is still 2000+ down here.  That area will be catching it closer to peak heating.  Still should have some nice storms down here.  Lots of rain to add to the already lots of rain!

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The Iceman

The Iceman

Posted
Posted

SVR watch hoisted for all of the CWA. Fairly strong wording.

95% severe wind probs 

60% 65kt or greater wind probs as well

Quote 

Primary threats include...
     Widespread damaging winds expected with isolated significant
       gusts to 80 mph likely
     Scattered large hail and isolated very large hail events to 2
       inches in diameter possible
     A tornado or two possible

   SUMMARY...A line of strong to severe storms will continue east from
   central Pennsylvania. Embedded bowing structures should result in
   widespread damaging winds.

 

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