Mesoscale Precipitation Discussion 0689
NWS Weather Prediction Center College Park MD
701 PM EDT Mon Jul 14 2025

Areas affected...Central and Northern Mid Atlantic

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

Valid 142300Z - 150500Z

SUMMARY...Widespread flash flooding concerns will continue through
much of the Mid Atlantic with a threat of significant flash
flooding across the urban centers from Richmond to New York City.

DISCUSSION...Current radar mosaic across the Northeast and Mid
Atlantic U.S. indicates quite a robust convective footprint
situated southwest to northeast ahead of a trough just east of
Lake Erie. A strong line of thunderstorms currently extends from
northern VA up through southern PA in the central Mid Atlantic
with a relatively robust multi-cell cluster bisecting eastern PA
up through northern NJ and the Lower Hudson Valley in NY. PWATs
between 1.8-2.2" have plagued the Mid Atlantic and continue to be
a focal point for the heavy convective pattern leading to
widespread flash flood issuance's through the course of the
afternoon. Hourly rates between 2-3"/hr have been the reason for
such a broad scope of impact as the environment has amplified the
convective regime throughout the course of the day with the threat
now carrying through this evening.

Despite the loss of a traditional diurnal heat flux, remnant cold
pools scattered through a slowly weakening thermodynamic
environment will still act as a focus mechanism for convection,
especially within the well-defined multi-cell clusters in place
over northeast PA, northern NJ, and Lower Hudson of NY. Further
south, expect the current line of convection to continue
progression to the east with the line holding together beyond the
DC/Balt/Phi metro before fading as it encounters a bit more stable
air closer to the Atlantic. Further south into VA, thunderstorms
over the Shenandoah will eject eastward through the central
portion of the state, but will likely hold together through cold
pool maturation and encountering the most favorable thermodynamic
corridor along the eastern seaboard (3000-4000 J/kg MUCAPE from
the Potomac down through southern VA).

Recent HRRR/RRFS trends have been favoring the triangle between
DC/Lynchburg/Williamsburg and the area across northern NJ as the
greatest threats for heavy nocturnal convection with totals
between 2-4", locally higher anticipated in these respective
zones. This is a strong correlation with 18z HREF neighborhood
probs for >2"/6-hrs. hovering between 60-80% for southern zone
with >80% depicted across all of northern NJ. These signals are
coincident with some of the more significant flash flood
potential, even some prospects for life-threatening flash
flooding, especially in those more urbanized areas where run off
capabilities are maximized.

There is potential for some of the heavier rainfall to extend into
New York City proper which could lead to an elevated flash flood
risk with even potential for significant flash flooding in spots
across the metro. Best chances will occur in the first few hrs. of
the threat window, but totals exceeding 2" in a short span of time
could easily occur in the window. This is a quickly evolving
scenario across area.

Kleebauer

ATTN...WFO...AKQ...ALY...BGM...BOX...CTP...LWX...OKX...PHI...
RLX...RNK...

ATTN...RFC...ALR...RHA...TAR...TIR...NWC...

LAT...LON   42267414 42227383 42097356 41977334 41857318
            41557287 41357292 40957330 40687353 40467371
            40097399 39897400 39687420 39577437 39437480
            39327503 39147527 38967553 38777563 38587566
            38457570 38227578 38027589 37817601 37697605
            37327631 37077654 36957683 36857726 36787752
            36727787 36737834 36747873 36867923 36927979
            37117995 37478008 37808010 38198000 38467966
            38717921 38987884 39037869 39097812 39187788
            39287757 39417735 39427726 39537691 39817648
            40217625 40507607 41017588 41497539 41837484
            42227434