Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
330 AM EDT Mon Mar 16 2026
Day 1
Valid 12Z Mon Mar 16 2026 - 12Z Tue Mar 17 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE MID-ATLANTIC AND NORTHEASTERN U.S...

Broad axis of diffluence positioned over the Ohio Valley into the
Northeast will lead to multiple rounds of convection once east of
the Appalachian front. Warm moist air will continue to funnel
poleward ahead of a very amplified trough axis centered over the
Midwest to Mid-Mississippi Valley. PWATs across the Mid Atlantic
have already surged beyond 1", a solid 3 standard deviations above
normal compared to climatology putting into the 97-99th percentile
for mid-March. Expectation is for this surge to continue pushing
further north within the amplified flow east of the Mississippi
leading to a large swath of the east coast to exhibit an
environment favorable for at least the threat of heavy rainfall.

A multi-round scenario of convective impacts are anticipated as
weak mid-level perturbations usher north-northeast ahead of the
mean trough and cold front migrating through the Ohio Valley. Prior
to the cold front arrival and associated precip field along and
ahead of the front, moderate to locally heavy rains from
convective clusters could help prime local soils before the main
time frame of impact after 18z occurs. One of the trends within
guidance was a relatively skinny convective segment that will be
the main player in the higher rates exhibited in this setup. The
linear segment will be relatively progressive, but rates between
0.75-1.5"/hr at peak intensity are plausible as it moves through
the Mid Atlantic and Northeast leading to a threat for flash
flooding as it migrates into the Piedmont and urban zones
characterized within the Northeastern Megalopolis. Areal average
of 0.75-1.5" is forecast for much of the area from northern VA up
into NY state and Northeast New England. The maxima of over 2" is
still showing up within deterministic output via both global and
CAMs physics. The area of interest continues to point to
CT/RI/Southern MA as the primary spot for more appreciable totals
>2". This is supported via the neighborhood prob fields of 50-80%
for at least 2" by the latest 00 HREF output. Other notable areas
include high probs >70% for at least 1" aligned along the Blue
Ridge to the I-95 corridor for VA/MD/PA extending into the Lower
Hudson and Catskills area of NY state. Another axis of higher probs
exists across eastern ME and parts of Northern New England which
coupled with high SWE presence should allow for rapid snow melt and
potential for local hydrologic issues stemming from both the
precip and snow/ice melt. This signal was sufficient for
maintenance of the previous MRGL risk with only some minor
adjustments on the southern edge of the risk area to account for
the latest model trends.

The progressive nature of the precip should curb some of the flash
flood concerns making this a solid MRGL risk with perhaps a bump in
the risk magnitude if guidances trends more aggressive in QPF
output. For now, this is a classic setup for early spring
convection and modest flash flood prospects.

Kleebauer


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt