Mesoscale Precipitation Discussion 0234
NWS Weather Prediction Center College Park MD
1226 PM EDT Tue May 06 2025

Areas affected...Northern Mid-Atlantic into the Interior Northeast

Concerning...Heavy rainfall...Flash flooding possible

Valid 061625Z - 062225Z

SUMMARY...Developing convection this afternoon is expected to
repeat over areas of the Northeast and Mid-Atlantic where recent
rainfall has lowered flash flood guidance. Isolated rainfall
totals over 2 inches could lead to scattered areas of flash
flooding, with the most likely impact along the NY-PA border and
nearby areas.

DISCUSSION...A closed low over the Upper Ohio Valley continues to
churn and usher in broad southerly flow along the East Coast.
PWATs are highest along the immediate East and into New England,
where values range from 1.0-1.2" and near the 90th climatological
percentile, but the greater mix of instability and shear exists
just to the west from central New York to northern Maryland. Here,
GOES-E visible imagery depicts broken cloud cover allowing for
SBCAPE to increase over 1,000 J/kg in southeast PA, which
coincides with where the deepest convection has developed over the
last hour.

Thunderstorms are expected to continue building (although
scattered in nature) over the next few hours as instability
continues to grow and expand northward. However, a focus in
convection is possible along a weak frontal boundary/convergence
axis. All of this activity will become more widespread in
northeast PA/southern NY by about 20z once a shortwave rounding
the base of the upper trough very quickly pushes over the recent.
This increased ascent may allow for rainfall rates to approach
2"/hr and broader coverage of moderate rain, but more importantly
impact areas prone to flash flooding due to recent rainfall. NASA
SPoRT LIS 0-40 cm soil moisture is above 98th percentile for much
of northern PA and NY. This goes along with 3-hr FFG under 2"
(even as low as 1" in localized areas). The 12z HREF highlights
impressive probabilities for exceeding this FFG along the PA-NY
border just west of Binghamton by 21z this afternoon. Will
continue to monitor rainfall rates in case the need for more
considerable/significant language is needed this afternoon.

Snell

ATTN...WFO...ALY...BGM...BUF...CTP...LWX...OKX...PHI...

ATTN...RFC...MARFC...NERFC...NWC...

LAT...LON   43647667 43467564 42937467 41957436 40827468
            40007534 39507640 39807705 40867721 41787734
            42837786 43467764