AWUS01 KWNH 092129
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-100330-

Mesoscale Precipitation Discussion 0653
NWS Weather Prediction Center College Park MD
528 PM EDT Thu Jul 09 2026

Areas affected...Mid-Atlantic

Concerning...Heavy rainfall...Flash flooding likely

Valid 092127Z - 100330Z

Summary...Thunderstorms with max rainfall rates of 2-3"/hr will
continue to shift east from the I-95 corridor this evening. Flash
flooding is likely to continue with localized considerable impacts
possible.

Discussion...Lee-side surface troughing downstream of a mid-level
trough axis over the central Appalachians has produced heavy
thunderstorms and scattered flash flooding this afternoon over the
Mid-Atlantic States and in particular along the I-95 corridor. Low
level southwesterly flow is parallel to this trough axis and has
promoted repeating activity/propagation and rainfall rates of
2-3"/hr. Moisture is high with PW of 2.3" northeast from the DC
area to Philly and 2.1" from Richmond to NYC. Instability ahead of
the thunderstorm axis is elevated from earlier sunshine, 3000+
J/kg in eastern VA and the Delmarva and around 1500 J/kg in
central/southern NJ.

The lee-side trough will continue to shift east and allow further
development/repeating through the Mid-Atlantic coast this evening.
Urban environments are fewer and far between east of I-95, but
these rain rates should cause flash flooding no matter the
environment. That said, the threat for additional considerable
flash flooding is greatest in urban environments since rural FFG
is generally around 3"/hr in southern NJ and the Delmarva.
Development is generally scattered west of Richmond, but the
southern PW gradient over Richmond warrants inclusion of that
metro area in this discussion.

Recent HRRR and RRFS runs favor heavy rain to become a bit more
progressive through the evening, presumably from veering low level
flow with the approaching mid-level wave outpacing the progress of
the surface trough. However, a slower pace through the coast may
be reasonable, clearing the coast by around 03Z. The threat for
activity later this evening farther south in the Hampton Roads
area will be monitored.

Jackson

...Please see www.wpc.ncep.noaa.gov for graphic product...

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

ATTN...RFC...ALR...RHA...NWC...

LAT...LON   40397405 39567405 38137493 37517557 37137776 
            38007785 38857722 39197677 39637602 40087544 
            40327457