Mesoscale Precipitation Discussion 0862
NWS Weather Prediction Center College Park MD
818 AM EDT Tue Sep 18 2018

Areas affected...Southern New England

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

Valid 181217Z - 181817Z

Summary....A localized flooding threat continues this morning
ahead of Post-Tropical Cyclone Florence.

Discussion...A broad shield of steady rainfall, and locally more
intense rates, continues to push northeastward into New England. A
general 1 to 3 inches has fallen thus far across northern MA into
southern VT and NH. Limited instability has kept rainfall rates
and the flash flood threat low to this point. Post-tropical
cyclone Florence was moving into far southern NY and western MA as
of 12z, with a warm front extending east northeast from the
center. Low level moisture transport will continue to increase
ahead of the low along/near the warm front. This should continue
to gradually increase instability into the area...allowing for an
uptick in embedded heavier convective cores within the broader
rain shield.

Expect an additional 1-3" of rainfall through the morning hours
across central/northern MA into southern NH and southern ME. Even
with weaker rates, this may cause some areal flooding concerns,
with storm total rains approaching 3-5" in spots. Any embedded
heavier convective cores will result in a localized flash flood
threat as well...especially in any more susceptible urban areas.
The greatest focus of rains should continue to be ahead of
Florence, near the warm front. South of the warm front,
instability is higher, but shower coverage should be less. Thus
while localized heavy rates are more likely here...the areal
coverage and magnitude of total amounts should be lower.

Chenard

ATTN...WFO...ALY...BOX...GYX...

ATTN...RFC...NERFC...

LAT...LON   43787032 43606979 43157000 42407085 41987162
            41867235 41977306 42477351 43087233 43297204
            43697099