https://www.wpc.ncep.noaa.gov/metwatch/metwatch_mpd_multi.php?md=0925&yr=2025
Mesoscale Precipitation Discussion 0925
NWS Weather Prediction Center College Park MD
1025 AM EDT Wed Aug 13 2025
Areas affected...Portions of the Central Appalachians and
Mid-Atlantic
Concerning...Heavy rainfall...Flash flooding likely
Valid 131425Z - 132025Z
SUMMARY...Clusters of heavy showers and thunderstorms with locally
extreme rainfall rates will tend to expand in coverage over the
next several hours. Scattered areas of flash flooding will
gradually become likely, and especially later this afternoon
closer to the I-95 corridor of the Mid-Atlantic where an urban
flash flood threat is expected to evolve.
DISCUSSION...The latest satellite and radar imagery shows a band
of heavy showers and thunderstorms moving into northern WV, and
the latest trends show cooling cloud tops associated with this
activity.
This convection is associated with the southwest flank of
mid-level vort energy going into the central Appalachians which is
embedded within a very moist and moderately unstable environment.
MLCAPE values across northern WV and western MD, and areas east of
the Blue Ridge over the Mid-Atlantic, are locally on the order of
1000+ J/kg. However, the PWs are quite high and locally over 2
standard deviations above normal.
In fact, the 12Z RAOB soundings from KPIT and KIAD showed PWs of
1.86 and 2.22 inches respectively with tall skinny CAPE profiles
and elevated WBZ/freezing levels. This is strongly suggestive of a
very efficient and tropical environment that will promote highly
efficient processes for locally extreme rainfall rates that may
reach well into the 2 to 3+ inch/hour range.
Convection should tend to generally build in coverage over the
next several hours as this vort energy advances off to the east
across the central Appalachians and northern Mid-Atlantic region.
This will support heavy showers and thunderstorms advancing east
through central and northern WV, western MD and southwest PA in
the near-term.
However, as instability and convergent low-level flow becomes
better established this afternoon east of the Blue Ridge and into
the Chesapeake Bay region, there will likely be the development
and expansion of very heavy showers and thunderstorms across much
of northern VA, central to northeast MD and southern PA, including
areas along the I-95 corridor from Washington D.C. to Philadelphia.
The latest hires model guidance may be underplaying the rainfall
potential given the level of moisture that is in place, and there
will the influence of diurnal heating and orographics that will
also support an uptick in coverage of showers and thunderstorms.
Slow cell-motions and localized cell-training concerns coupled
with locally extreme rainfall rates may support some localized
rainfall totals of 3 to 5 inches. Areas of scattered flash
flooding will become likely in time, and this will include an
increasing urban flash flood threat near the I-95 corridor by
later this afternoon.
Orrison
ATTN...WFO...AKQ...BGM...CTP...LWX...PBZ...PHI...RLX...RNK...
ATTN...RFC...RHA...TIR...NWC...
DCA: +0.3 NYC: -0.3 BOS: -0.6 ORD: +0.4 ATL: +0.9 IAH: +1.0 DEN: +1.3 PHX: +1.4 SEA: +2.7
