E PA/NJ/DE Summer 2026 Obs/Discussion

[JTA66]

It's been a few years since the lawn's been this lush and green in late August.

77F/DP 73F

[ChescoWx]

Most spots dry out a bit today with sun returning we could see a couple showers toward evening especially across southeast parts of the area. A bit less humidity today and especially tomorrow before the chances of showers increase again by Thursday afternoon into the night. The weekend looks to continue shower chances as we continue to erode any drought concerns across the area.

[Chadzachadam]

DPs are still nasty this morning, hanging in the low-mid 70s. should get some relief this evening and tomorrow

[Hurricane Agnes]

I actually picked up some back-built leftovers yesterday for 0.49" total for the day and a 2-day event total of 1.06".

Had a low of 73 and a high of 87.  The dews have been annoying and it's currently 84 with dp 73.

[The Iceman]

5% TOR for extreme SE PA/S NJ/DE. Meso models this morning really liking this area for both strong storms and flash flooding. 06z 3K NAM and 12z HRRR are both nasty later on. NAM with a supercell threat while the HRRR is showing a huge QLCS for this evening. 

https://www.tropicaltidbits.com/analysis/models/nam3km/2026082006/nam3km_mslp_pcpn_frzn_neus_14.png

 

https://www.tropicaltidbits.com/analysis/models/hrrr/2026082012/hrrr_ref_frzn_neus_12.png

[ChescoWx]

We are under a flood watch thru 2am for between 1 to 2 inches of rain and maybe more for some spots that get under a thunderstorm. We will get cooler tomorrow and that will last through the next week with temperatures mainly in the upper 70's to near 80 degrees for high temperatures. We should see nighttime lows back into the 50's by early next week.

[Mikeymac5306]

1 hour ago, The Iceman said:

5% TOR for extreme SE PA/S NJ/DE. Meso models this morning really liking this area for both strong storms and flash flooding. 06z 3K NAM and 12z HRRR are both nasty later on. NAM with a supercell threat while the HRRR is showing a huge QLCS for this evening. 

https://www.tropicaltidbits.com/analysis/models/nam3km/2026082006/nam3km_mslp_pcpn_frzn_neus_14.png

 

https://www.tropicaltidbits.com/analysis/models/hrrr/2026082012/hrrr_ref_frzn_neus_12.png

Unless the sun comes out and bakes this afternoon I don't see it. 

[Chadzachadam]

another case where strong storms are possible in the evening but we get some rain early in the day. wonder if we fail the same way as we have earlier this summer, with too much going on and not enough instability left by the time the storms are expected

[RedSky]

Drought buster incoming

 

[The Iceman]

Mesoscale discussion out

 

Mesoscale Discussion 2052
NWS Storm Prediction Center Norman OK
Aug 20, 2026 17:53Z

Areas affected...parts of southeastern Pennsylvania...central and southern New Jersey...north central and eastern Virginia...much of Delaware and Maryland.

Concerning...Severe potential...Watch likely

Valid 201753Z - 202000Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorms are likely to develop and intensify through 4-6 PM EDT, accompanied by the risk for a couple of tornadoes initially and increasing potential for strong to severe gusts spreading toward coastal areas into early evening.

DISCUSSION...Moderate to strong boundary-layer destabilization is ongoing across much of the northern Mid Atlantic, particularly within seasonably high moisture content air advecting northward through the coastal plain, to the east of deepening (albeit weak) surface troughing to the lee of the Blue Ridge. This is occurring downstream of mid-level troughing, with at least a couple of convectively generated perturbations and belt of augmented westerly flow (30-50 kt in the 700-500 mb layer).

It appears that associated forcing for ascent may increasingly begin to impact a corridor from central Maryland through southeastern Pennsylvania by 20-22Z, if not a bit earlier, supporting the initiation of intensifying thunderstorm development. At least initially, this may include a few evolving supercell structures in the presence of strong deep-layer shear. 

Downstream of a developing wave along a weak low-level baroclinic zone strengthened by differential heating, low-level hodographs are forecast to remain modest to weak. However, they may still be sufficient to contribute to potential for a couple of tornadoes, aided by appreciable near-surface buoyancy developing in associated with insolation, warm advection and dew point increases into the lower 70s F.

Otherwise, at least some upscale growth of initial storms will contribute to increasing potential for damaging surface gusts, with additional thunderstorm development southward along and east of the deeper lee surface troughing.

..Kerr/Smith.. 08/20/2026

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

ATTN...WFO...PHI...AKQ...CTP...LWX...

MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN

[Kevin Reilly]

26 minutes ago, The Iceman said:

Mesoscale discussion out

 

Mesoscale Discussion 2052
NWS Storm Prediction Center Norman OK
Aug 20, 2026 17:53Z

Areas affected...parts of southeastern Pennsylvania...central and southern New Jersey...north central and eastern Virginia...much of Delaware and Maryland.

Concerning...Severe potential...Watch likely

Valid 201753Z - 202000Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorms are likely to develop and intensify through 4-6 PM EDT, accompanied by the risk for a couple of tornadoes initially and increasing potential for strong to severe gusts spreading toward coastal areas into early evening.

DISCUSSION...Moderate to strong boundary-layer destabilization is ongoing across much of the northern Mid Atlantic, particularly within seasonably high moisture content air advecting northward through the coastal plain, to the east of deepening (albeit weak) surface troughing to the lee of the Blue Ridge. This is occurring downstream of mid-level troughing, with at least a couple of convectively generated perturbations and belt of augmented westerly flow (30-50 kt in the 700-500 mb layer).

It appears that associated forcing for ascent may increasingly begin to impact a corridor from central Maryland through southeastern Pennsylvania by 20-22Z, if not a bit earlier, supporting the initiation of intensifying thunderstorm development. At least initially, this may include a few evolving supercell structures in the presence of strong deep-layer shear. 

Downstream of a developing wave along a weak low-level baroclinic zone strengthened by differential heating, low-level hodographs are forecast to remain modest to weak. However, they may still be sufficient to contribute to potential for a couple of tornadoes, aided by appreciable near-surface buoyancy developing in associated with insolation, warm advection and dew point increases into the lower 70s F.

Otherwise, at least some upscale growth of initial storms will contribute to increasing potential for damaging surface gusts, with additional thunderstorm development southward along and east of the deeper lee surface troughing.

..Kerr/Smith.. 08/20/2026

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

ATTN...WFO...PHI...AKQ...CTP...LWX...

MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN

This seems underway just northeast of Dover Delaware moving NE into Southwestern NJ that is some pretty heavy-duty flooding rains there moving NE.

[Kevin Reilly]

Severe thunderstorm watch moved to a tornado watch SE Pa points South and southeast 

[LVblizzard]

That line coming through Lancaster looks nasty. Wouldn’t be surprised if it leaves a trail of wind damage and even a tornado or two.