602
FXUS61 KLWX 180121
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
921 PM EDT Thu Jul 17 2025

.SYNOPSIS...
A cold front will move through the area overnight. The front
will become stationary over the area Friday, before returning
northward across the area on Saturday. A stronger cold front
will move through on Sunday night.

&&

.NEAR TERM /THROUGH FRIDAY/...
Isolated strong thunderstorms near BWI Airport and Annapolis are
showing signs of weakening quickly as they move east-southeast.
An isolated strong thunderstorm, dropping southeast across the
Virginia Piedmont, is holding strong at this time but should
weaken in another hour or two. Additional showers and
thunderstorms are noted moving toward the east-southeast across
the central Appalachians into the northern Shenandoah Valley.
This activity is weakening, but still shows signs of heavy
rainfall and occasional lightning.

As we get into late evening, convection should dwindle to not
much more than an isolated shower or two or sprinkles. In areas
where rainfall isn`t an issue overnight, some patchy fog could
develop and reduce visibility to a mile or two. Some valleys in
the west would be more susceptible to encountering this fog.
Low temperatures will drop into the 70s overnight, while
dewpoint temperatures drop to the lower 70s or perhaps upper 60s
in some places. Thus, with this being said, humidity will
remain rich overnight.

As a cold front sinks southward, a light northerly wind could
help enhance drier conditions overnight for most areas.

The cold front is expected to stall out over the area on Friday.
This will allow for slightly cooler and less humid air to work
into northern MD, with dewpoints dropping into the 60s, and
temperatures only making it into the low to mid 80s. Further
south, the central Shenandoah Valley and central Virginia will
remain on the warm side of the boundary, with dewpoints holding
in the 70s and temperatures making it into the upper 80s. Dry
conditions are expected to start the day, but model guidance is
in good agreement that showers and thunderstorms will form again
Friday afternoon as a convectively generated disturbance
approaches from the west. Coverage of these showers and storms
should be greatest along/on the warm side of the boundary
(central Shenandoah Valley/central Virginia), where more
instability will be present, with little to no coverage expected
as you move toward more stable air in place over northeast
Maryland. Like many days over the last week, the airmass in
place on the warm side of the boundary will be very moisture
rich, unstable, and saturated in the vertical. Model soundings
show MLCAPE values around 1500-3000 J/kg and PWAT values in
excess of 2 inches on the warm side of the boundary, which
should make storms capable of producing very heavy rainfall.
This raises concerns for flooding once again, primarily from the
central Shenandoah Valley into central Virginia, where WPC has
a Slight Risk for excessive rainfall. Numerous CAMs show
localized maxes of 2-5 inches in this region Friday. A Flood
Watch for flash flooding may need to be considered for this area
during subsequent shifts. A threat for isolated damaging winds
may also be possible on the warm side of the boundary. SPC
currently has a similar area outlooked in a Marginal Risk,
driven by damaging winds.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
Additional showers and thunderstorms may be possible again on
Saturday as another weak disturbance approaches from the Ohio
Valley. The primary focus should again be in southwestern
portions of the forecast area, where the greatest instability
and moisture content will reside, but an afternoon storm can`t
be ruled out anywhere across the area. High temperatures will be
in the 80s (mid-upper 80s south, lower 80s north), with
dewpoints in the 70s.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
A cold front will move through the area Sunday evening. Ahead of the
cold front, there will be deep NW flow with lack of sfc convergence.
If anything manages to develop, it will likely become severe, but
any storms will likely be isolated in coverage. Looks like an SMW
day. Cold front will push south of the area by Monday morning ending
any t-storm risk.

Behind the front Monday, sfc dewpoints will drop into the 50s, which
will be a welcome relief to the oppressive humidity of the past
several weeks. Height rises will prevail during the middle part of
the week leading to a substantial warming trend and inhibiting
convection. Height rises peak on Thu as subtropical ridge over the
Mid-South inches closer to the area. Subtropical ridge will start
breaking down as Northeastern U.S. trough deepens and promotes
height falls across the region. Expect thunderstorm chances to
increase as a result.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
VFR conditions with afternoon chances for showers and
thunderstorms are expected each of the next three days. There
is also some hint in guidance that sub-VFR ceilings may try to
work into the area Friday night. Coverage of storms is largely
expected to remain low Friday as well, except in the vicinity
of CHO, where a higher coverage of storms is expected. Saturday
may also feature a similar pattern, where coverage of storms is
higher in the vicinity of CHO and lower further northeast.

Winds decreasing this evening. Winds should stay light and
gradually veer around from southwest to northwest to northeast
later tonight into Friday morning. Winds will remain light
Friday, and may be out of the east for a good portion of the
day. Winds should become south to southeasterly on Saturday.

Isolated t-storms expected Sunday. Dry Monday behind a cold
front.

&&

.MARINE...
A cold front will move over the waters later tonight, causing
the winds to shift to out of the north late tonight, and then
east to northeast Friday. Winds will then turn out of the south
on Saturday. An SMW for thunderstorm winds can`t be ruled out
Friday or Saturday afternoon.

Isold t-storms Sun may produce strong wind gusts and require SMWs.
SCA conditions possible Sun night into Monday behind a cold
front.

&&

.TIDES/COASTAL FLOODING...
Anomalies have started to decrease within west to southwesterly
flow. Annapolis is forecast to near Action Stage during high
tide cycle Friday morning. Otherwise, the threat for tidal
flooding appears low.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ533-534-
     537-541>543.

&&

$$

SYNOPSIS...KJP
NEAR TERM...KLW/KJP
SHORT TERM...KJP
LONG TERM...LFR
AVIATION...LFR/KLW/KJP
MARINE...LFR/KLW/KJP
TIDES/COASTAL FLOODING...LFR