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E PA/NJ/DE Summer 2019 OBS Thread


Rtd208
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Was in the Narberth area in Delco when the sky just opened up.  Heard all the EAS flash flood warnings come through on my way back home through Manyunk and on up to Chestnut Hill.  Lots of standing water.  Got an additional 0.56" of rain from the last round giving me a total of 1.30" for the day at post time.  Currently 63 with a little leftover light rain.

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Quite the discussion from Mt.Holly ref late weekend/next week.

.LONG TERM /SUNDAY THROUGH FRIDAY/... 
  So it continues. A stormy period looks to be taking shape Sunday  
  through Friday. The Mid-Atlantic continues to be sandwiched in  
  between the mid-level high to our south and the mid-level low to our  
  north. In between, a somewhat zonal flow this week with a handful of  
  fast moving perturbations.   
   
  Latest model runs have consistently shown a front approaching the  
  Mid-Atlantic Sunday and Monday before stalling it near or in the  
  area for the rest of the week. The forecast problem comes down to  
  timing the best chances for convection in this regime, which is tied  
  to low-amplitude (and likely convectively-generated/maintained)  
  perturbations moving eastward in the quasi-zonal mid/upper flow  
  across the eastern U.S. throughout this period. Unfortunately, this  
  is of low predictability, with models once again exhibiting  
  variations run to run and model to model. Thus, the approach for the  
  medium-range forecast remains the same: higher-than-climatology PoPs  
  for most of the period and near to slightly above average  
  temperatures. In general, the updated forecast is quite close to  
  continuity. 
   
  The main changes are with the Sunday/Monday forecast, where models  
  are showing slow convergence on the convective evolution. The  
  aforementioned cold front will be approaching the lower Great Lakes  
  east-northeast to northern/central New England on Sunday, with  
  several weak perturbations moving west-to-east near the boundary.  
  Convection should readily develop along/downstream of the front by  
  afternoon, mainly to our north/west but probably also in our CWA as  
  well. The 00z GFS is depicting a stronger vort max approaching the  
  northern Mid-Atlantic during the evening, with a round of  
  strong/widespread convection in our area by this time. The 00z ECMWF  
  is fairly similar, which provided enough confidence to raise PoPs to  
  high-chance and even likely in northern portions of the CWA Sunday  
  afternoon/night. Precipitation will wane late Sunday night as  
  nocturnal stabilization takes over and the strongest large-scale  
  lift moves to our east.  
   
  The CAPE/shear parameter space would be sufficient for severe storms  
  Sunday afternoon/evening, and I am rather concerned the GFS is  
  underdoing instability in the pre-frontal warm sector given  
  increasingly warm/moist conditions. Moreover, BUFKIT  
  soundings/hodographs suggest a substantial amount of low-level  
  shear/helicity may exist. Will need to watch Sunday afternoon/night  
  closely for the severe-weather threat in the coming days. 
   
  After perhaps a brief reprieve late Sunday night into Monday  
  morning, chances of strong convection return Monday afternoon. Both  
  the 00z GFS and ECMWF depict another strong perturbation moving  
  through the northern Mid-Atlantic during the afternoon/evening. Once  
  again, the CAPE/shear parameter space is favorable for severe  
  storms, though shear may be somewhat weaker than the previous day.  
  However, the pre-frontal warm sector may be more unstable (using  
  model sounding comparisons Sunday versus Monday). Complications from  
  antecedent convection will exist (increasing the uncertainty in the  
  forecast by this point), not to mention the model volatility already  
  in place with the perturbations responsible for the larger-scale  
  lift associated with the convection. Nevertheless, I am becoming  
  quite concerned with the severe threat both of these days, and hydro  
  issues will be an increasing concern as well given the multiple  
  rounds of storms that may affect the area. 
   
  Speaking of, the forecast does not look much better Tuesday onward.  
  Models show little southward progress of the front and more low- 
  amplitude perturbations affecting the region the rest of the week.  
  Variability in timing/track of these vorticity maxima is quite high  
  during this period, but the pattern is certainly suggestive of a  
  stormy period...with hydrologic concerns only increasing if such a  
  pattern were to verify. 
   
  && 

Upton:

.LONG TERM /SUNDAY THROUGH FRIDAY/...
The main story of the long term will be with a frontal boundary that
approaches on Sunday and then likely stalls over the Tri-State on
Monday. This front may linger near the region through the rest of
the week. Confidence in the exact location of the front remains
uncertain later in the week, with the best consensus of model data
indicating the front remains near the region.

The 12z ensemble means continue to show an upper level low over
southeast Canada on Sunday becoming mostly locked in place through
the middle of next week. This is due to a blocking pattern at higher
latitudes. Ridging sets up over the western Atlantic through the
week. The surface frontal boundary will become nearly stationary
near the region next week between the upper low to the north and
western Atlantic ridging.

Chances for showers and thunderstorms increase Sunday afternoon and
evening as the front nears. Shortwave energy appears weak so have
capped PoPs off at 50 percent. A little better defined shortwave and
frontal wave is progged to move through late Monday afternoon and
Monday night. Have increased PoPs to likely based on some better
support aloft (shortwave energy) as well as some continuity among
the models with the frontal wave. With the front near the region on
Tuesday, the chance for showers and possible storms continues.
Guidance over the last several runs has hinted that the front may
try to sink south on Wednesday. Have not completely gone dry yet as
this may be too aggressive. Unsettled weather may continue for the
end of the week. A more well defined shortwave is currently
indicated by the GFS/ECMWF/CMC to act on the front to bring
precipitation late Thursday into Friday.

While the long term looks unsettled, there will be periods of dry
conditions and periods of precipitation. The exact timing remains
uncertain.

Temperatures through the long term will average near to slightly
above normal.

&&

 

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The 18z GFS looks very wet over the next several days. The 18z NAM catching on a bit as well. The upcoming week should have several bouts of heavy rain/severe weather. We could see some showers and maybe storms move thru overnight before things really start to ramp up tomorrow and continue thru most if not all of the upcoming week.

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Was just under a line of heavy rain. Had made it up to 85 this afternoon just after 2:30pm after a non-measurable brief sprinkle came through around 1 pmish that dropped the temp about 5 degrees from the high at the time... but definitely added some humidity.

Currently up to 0.11" with it so far (seems to be moving quickly) and temp is down to 78 and falling.

radar-zoom8-06162019.png

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0.27" of rain with our 1st rain event of the week.  2.87" so far this month which is 0.73" above normal here in NW Chester County PA. We are now at 26.51" of w.e. so far this year which is 123% of normal through today.

Through today the Philly burbs have not seen a 90+ day - however the PHL airport has already seen one such day. To highlight the PHL Airport heat island effect - while Philly averages 21 days of 90+ in a normal summer season....here in the NW suburbs of Philly we have only experienced 3 years in the last 20 years of records with even 10 or more days that surpass the 90 degree mark.

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