Mesoscale Precipitation Discussion 1165
NWS Weather Prediction Center College Park MD
1028 AM EDT Tue Sep 01 2026
Areas affected...Far Northeast PA...Northern NJ...Southeast NY and
Western Long Island
Concerning...Heavy rainfall...Flash flooding possible
Valid 011428Z - 012028Z
SUMMARY...Locally heavy showers and thunderstorms with some
occasional cell-training will pose a concern for some isolated
areas of flash flooding going through the mid-afternoon hours.
This may include some urban impacts.
DISCUSSION...The latest GOES-E IR satellite imagery shows cooling
convective tops associated with a corridor of locally heavy
showers and thunderstorms across far northeast PA and adjacent
areas of south-central to southeast NY. The activity is largely
being driven by a corridor of relatively stronger warm air
advection and moisture transport advancing across the northern
Mid-Atlantic region as a warm front attempts to lift off to the
northeast across the region.
Most of convection is somewhat elevated with MUCAPE values of near
1000 J/kg pooled along the front. PWs though are rather high with
values of 1.75 to 2.0 inches in place. The latest RAP analysis
along with VWP data indicates the nose of a 30 to 35+ kt westerly
low-level jet across northern PA which is suggesting some speed
convergence along with the advance of stronger isentropic ascent
to facilitate some of the recent convective trends. Additionally,
there is the southeast advance of a shortwave trough across New
England with nearby divergent flow aloft at least modestly
overlapping the front along with some of the low-level support.
Some fairly decent effective bulk shear of 30 to 40 kts is in
place and this kinematic environment coupled with the available
moisture and instability may yield some rainfall rates locally as
high as 1.5 inches/hour. The alignment of the convection with the
deeper layer flow suggests some cell-training concerns, and there
may be some highly localized swaths of 2 to 3+ inch rainfall
totals going through the early to mid-afternoon hours as the
overall convective threat shifts down to the southeast.
The latest models are struggling with the current activity, but
the environment along and just south of the warm front may tend to
become more supportive of convection over the next several hours
as boundary layer instability increases. FFG values are locally
rather low across northern NJ and areas close to New York City.
This coupled with the rainfall threat may support an isolated
threat of flash flooding and potentially some urban impacts.