Mesoscale Precipitation Discussion 0899
NWS Weather Prediction Center College Park MD
322 PM EDT Sun Aug 18 2024
Areas affected...Western Connecticut
Concerning...Heavy rainfall...Flash flooding likely
Valid 181922Z - 182252Z
Summary...A localized cluster of cells continues to produce very
impactful flash flooding over western Connecticut. Cells
developing upstream will feed into this complex, which will
continue the threat of significant flash flooding.
Discussion...Radar continues to track a localized but very
efficient cluster of cells which has persisted throughout the
morning across western Connecticut. Nearly stationary cell motions
and extreme rainfall rates exceeding 3"/hr at times has led to
considerable to locally catastrophic impacts across the area, with
radar estimates of 7-9" of rainfall noted as of writing.
This focused area of extreme rainfall likely focused along a
mesolow providing convergence for ascent and enhanced low-level
inflow across the region. Upstream of the activity, SFC-850 ALPW
and recent ASCAT surface winds also depict a well defined area of
confluence embedded within a moist conveyor feeding into the
convection. With continued heating, the first signs of cumulus
streets and enhanced vertical development are noted upstream,
which suggests the area is destabilizing. Thus, additional cells
are expected to develop and feed into the area in the presence of
the low level forcing.