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Low probability isolated 4+" of rain in a couple of spots NJ/LI between 04z/Fri 8/7 and 12z Sat 8/8


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LOW chance of exceeding 4" but this is worthy of awareness, I think. 

Have reviewed most of the typically used 12z/6 modeling, and WPC/SPC guidance. The scenario is a weak wsw flow aloft at 700 mb, over a very moist (near 15C dew point) 850MB vorticity rich wind shift across NJ (sse-sw) with 500mb vorticity maxima passing newd within an approaching 500mb trough that doesn't swing its broad axis through our NYC forum until about 12z Saturday.  Dewpoints are already generally in the mid 60s with PWAT 1.6-1.8",-not overly wet, but with slow movers, plenty to allow for potentially excessive rainfall. How it all works is not clear and odds are that more than 4" of rain won't occur but have seen 12z/6 SPC HREF MAX precip guidance nears 10" in 1 spot of east central NJ and spotty 10+ s of LI. Best axis: unsure but for now along or s of I80 through LI or southward down to near I-195 (Ocean Mercer) counties. 

It should light up late tonight in central or northern NJ into LI and continues into forenoon Friday,. (Could be one or 2 isolated wet microburst SEVERE's?).

For nw NJ, if there is very little tonight then I could see isolated svr thunderstorms in ne PA drift into nw NJ and se NYS late in the afternoon or evening and then continue to LI as showers Friday night.   Low prob of occurrence.          SPC has no risk and wind fields are generally a little too light. 


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Cream Ridge and Jacobstown NJ... in or extremely close to our NYC forum (Monmouth and very northern Burlington County) 3.19 and 2.93 respectively since 6AM. 

Respect the rainfall rates in what I think may be a hybrid SHARS situation... subtle.  Note also a possible connector-training event may???? be developing JFK-ABE.  I think radar is underestimating the yield on this.  918A/7

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Have to be careful with some of these reports. I saw 1 report from wx underground at 6+ inches near PHL... checked the station and found it had started at 3" as a baseline. Power outages maybe compromising some of the data.  In any case,  I'll try and check some of this data later tonight---  if I can wake up at 1130PM. 

So far for our area, am looking at this as routine showers/thunderstorms with a + QPF axis near I195  but it isn't over.  Diurnally it should calm down during the night but with the trough aloft coming through and remaining moist low levels, we might get a cluster or two of heavy showers/iso thunderstorms overnight. Prospects for severe in our forum area overnight look very limited-and not expecting any but I could see another inch or 1.5" of rain in a few spots of NJ overnight?  

I am pretty certain the radar is underestimating storm total precip... have checked MARFC multi sensor ending 7P.  Looks about 1" shy of reality. Here it is.  (820P/7)

Screen Shot 2020-08-07 at 8.13.27 PM.png

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Final eval: no 4+ our area and SPC HREF potential 10+ wrong for our area.

Max our area, that I could quickly find. Rutgers climate site Cream Ridge 2.84.  Weatherunderground Cream Ridge 3.53 and nearby Jacobstown just across the Burlington County border 3.19.  

I saw one posted 6+ inch report in PHL CWA, in se PA Chester County.


(941AM -Added CoCoRAHS visual of 24 hour rainfall ending roughly 8AM Saturday and not inclusive of the pre 8AM Friday rain.)



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