Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
343 AM EDT Mon Sep 15 2025
Day 1
Valid 12Z Mon Sep 15 2025 - 12Z Tue Sep 16 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
EASTERN NORTH CAROLINA AND SOUTHEASTERN VIRGINIA...

Current WV satellite indicates a maturing mid-level trough situated
just off the SC/GA coast with a surface low analyzed 150 miles
east of KILM, meandering around as the upper pattern evolves.
Expectation is the surface low to be pulled northwest over the
course of the D1 with a closer proximity to the NC coast by later
this afternoon and evening with a strong east to northeast flow
anticipated over the northern flank of the SLP. Current NAEFS
ensemble output is forecasting a stout +2/+3 deviation u-vector
wind component with origins straight off the Atlantic, a signal
coincident with a robust low-level moisture advection regime into
the northern and western flank of the low pressure center. PWATs
are anticipated to climb closer to +1.5 deviations above climo,
good enough for outputs within the 1.5-2" mark across much of
eastern NC into the VA Tidewater. The persistence in the low-level
flow and modest ascent located within the maturing deformation axis
will lead to a long period of heavy rainfall situated across the
aforementioned areas above, allowing totals to reach between 2-4"
over areas along and east of I-95 and north of US70 in NC, and
between 1-3" across the VA Tidewater.

00z HREF is pretty robust in the depiction for the above totals
forecast with some embedded convective elements likely to spur
rates between 1-2"/hr at times, mainly across northeast NC where
strongest 850-700mb FGEN signals align early this evening into the
overnight hours. HREF neighborhood and EAS probs for >2" are pretty
high for the region with the neighborhood >3" signal settling
between 50-90% for the zone referenced above in NC. Antecedent
drier soils leading in will help curb some of the flash flooding
concerns initially, but the long-standing heavy rain threat, and
embedded convective potential the second half of the forecast could
lead to isolated/scattered bouts of flash flooding as the event
continues. The previous MRGL risk was expanded to align with the
trends in the >3" neighborhood prob signal in the HREF, and to
account for the latest ECMWF EFI signal extended a bit further west
than where we had the previous MRGL risk located.

Kleebauer


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