Mesoscale Precipitation Discussion 0111
NWS Weather Prediction Center College Park MD
254 PM EDT Sat Mar 23 2024

Areas affected...southern New England, southern New York state

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

Valid 231848Z - 240100Z

Summary...Areas of 0.25-0.7 inch/hr rainfall rates are spreading
northeastward into southern New England.  These rates are expected
to persist for around 3-5 hours or so, resulting in at least minor
flood/flash flood issues through 01Z.

Discussion...A relatively focused areas of heavy rainfall
continues to migrate northeastward along and ahead of a
strengthening low-level cyclone centered over Maryland.  The area
of heavier rain continues to be supported by strong convergence on
the nose of a stout (70 kt) low-level jet extending from open
waters east of the Mid-Atlantic into Long Island, NY.  Over the
past several hours, areas of 0.5-0.7 inch/hr rain rates have been
noted, resulting in a number of road closures and creeks entering
flood stage especially across eastern Pennsylvania and New Jersey.

The area of heavier rain appears to be shifting northeastward into
southern New York State and Connecticut while expanding across
Rhode Island and southern Massachusetts.  This pattern will likely
result in about a 3-5 hour period of heavier rainfall across the
discussion area, with totals reaching the 1-2.5 inch range during
that time.  These totals are likely to approach FFG thresholds
(generally in the 2-2.5 inch/hr range/locally lower in urban
areas) on at least an isolated basis.  Widespread areas of minor
flood impacts are expected, and isolated flash flood instances are
possible in this regime.  Current trends suggest that heavier
rainfall should end across southern New York state/Long Island by
around 21Z, while persisting across eastern Massachusetts/Rhode
Island and vicinity through 01Z.  Given warm advection across
areas of southern New Hampshire, a few areas of snow-melt-induced
excess runoff cannot be completely ruled out.

Cook

ATTN...WFO...ALY...BGM...BOX...GYX...OKX...PHI...

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

LAT...LON   43637084 42527001 41416983 40217166 40367419
            40967464 41637453 42587355 43407207