Mesoscale Precipitation Discussion 0854
NWS Weather Prediction Center College Park MD
401 PM EDT Tue Aug 23 2022
Areas affected...Southern New England
Concerning...Heavy rainfall...Flash flooding possible
Valid 232000Z - 240100Z
SUMMARY...Thunderstorms displaying occasional training
characteristics could produce localized flash flooding,
particularly in more heavily urbanized communities.
DISCUSSION...18Z surface analysis showed a frontal boundary draped
across southern New England while southwesterly 850mb flow
continued to intersect the boundary. 850-300mb mean winds are in a
fairly uniform SW flow pattern aloft as well, which favors the
potential for training thunderstorms. According to SPC RAP
mesoanalysis, PWs across southern New England ranges between
1.6-1.75" and MLCAPE is 1,000-1,500 J/kg as of 19Z. The front will
lift north gradually throughout the evening and the storms will
propagate northeast closer to the Boston metro area. MRMS
instantaneous rates have been above 2.5"/hr within the heaviest
storms, and FLASH CREST max unit streamflow has generated 200-600
cfs/smi in the Providence area. Local observations near Taunton
and west of Springfield have reported >1.5" over the last hour.
The latest HRRR shows several more hours worth of storms possible,
which given the persistent southwesterly flow intersecting the
front, gives reason to believe the potential for training storms
will linger into the evening rush hour. Localized flash flooding
is possible in the more heavily urbanized areas and in low lying,
poor drainage spots.