District of Columbia

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
317 PM EDT Wed Jul 9 2025

.SYNOPSIS...

A surface trough will remain across the area through Thursday.
Weak high pressure will build over the area for the end of the
week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...

Low-level trough is expected to sharpen across the area through
tonight as a shortwave-trough approaches from the OH Valley.
This will provide stronger forcing and help sustain thunderstorms
longer into the night tonight. In other hand, recent NUCAPS
data from 1717Z indicate that air mass today is not as unstable
as it was yesterday. Not seeing the 3500 J/kg CAPE that I saw
yesterday. Northeast Maryland looks particularly more stable
and less humid today than yesterday. The 925-850 mb moisture
axis is also further west today and extends up the I-81
corridor from Augusta County VA up through Winchester,
Martinsburg, Hagerstown into Chambersburg PA. The radar trends
indicate that the cluster over Rockingham County will likely
merge eventually with the other clusters approaching the
Appalachians, posing a flood risk over parts of eastern WV.
Given these trends and moisture axis further west, have expanded
the Flood Watch to cover eastern WV and Washington County MD.
With time, this moisture axis is expected to shift northeast on
SSW winds. So, expect a later onset of thunderstorms in central
and northeast MD this evening when compared to yesterday. Given
the stronger forcing, expect thunderstorms to last well into
the overnight hours, especially for the I-95 corridor. Overall,
the flood risk looks higher than the severe threat.
(snip)