Mesoscale Precipitation Discussion 0635
NWS Weather Prediction Center College Park MD
1250 PM EDT Thu Jul 10 2025

Areas affected...Vermont and New Hampshire...Far Western Maine

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

Valid 101650Z - 102250Z

SUMMARY...Slow-moving showers and thunderstorms anchored near the
higher terrain of the Green and White Mountains may result in
isolated to scattered instances of flash flooding going through
the afternoon hours.

DISCUSSION...The latest GOES-E visible satellite imagery in
conjunction with radar is showing the gradual development and
expansion of slow-moving shower and thunderstorm activity along
the higher terrain of the Green and White Mountains of Vermont and
New Hampshire respectively.

The activity is being strongly influenced by orographic ascent
within an increasingly unstable environment characterized by
MLCAPE values of about 1000 J/kg. PWs are relatively moist with
values up to about 1.5 standard deviations above normal, and this
will favor convective cells capable of producing heavy rainfall
rates of up to 1 to 2 inches/hour.

Going through the afternoon hours, the arrival of some shortwave
troughing/DPVA from southeast Canada in conjunction with
additional diurnal heating should promote some additional
expansion of convection that will be embedded within rather weak
steering flow. The cells will be aided by terrain-driven
circulations that may tend to allow for some of the cells to be
nearly stationary and anchored along the upslope areas of the
higher terrain.

The 12Z HREF and recent HRRR solutions suggest some localized 2 to
4+ inch rainfall amounts will be possible, and this coupled with
the rugged terrain of the Green and White Mountains may support
there being some isolated to scattered instances of flash flooding.

Orrison

ATTN...WFO...ALY...BTV...GYX...

ATTN...RFC...TAR...NWC...

LAT...LON   45267109 45067051 44587050 43567113 42957178
            42767239 42967331 43727347 44397329 44687296
            44857234