558
FXUS61 KLWX 171954
AFDLWX

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

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

&&

.NEAR TERM /THROUGH TONIGHT/...
Current satellite imagery shows mostly sunny skies, with some
cumulus scattered about the area. Conditions are hot and humid,
with Heat Advisories in effect for roughly the eastern half of
the forecast area. Temperatures are nearing their highs for the
day in the low to mid 90s, while dewpoints are holding in the
low to mid 70s. This is resulting in heat indices near or in
excess of 100 degrees across much of the area. A southwesterly
breeze at around 10-20 mph may be providing some slight relief
from the heat.

Surface observations suggest that there is a weak surface trough
extending roughly from Petersburg, WV northeastward to just west
of Hagerstown, where westerly winds further west are meeting
southwesterly winds further to the east. The cumulus field is
starting to deepen slightly in the vicinity of this surface
trough, and some showers and a few thunderstorms are starting to
form across the higher terrain in the Alleghenies. The main
forecast question today is just how much thunderstorm activity
will get going along this surface trough later this afternoon
into this evening as it slowly sags toward the south. Most
guidance suggests that coverage of storms should remain low, and
as a result, we`re forecasting just isolated thunderstorms this
afternoon. While most locations should remain dry, the
background environment does appear to be favorable for
producing strong winds if a more robust storm were to become
established. SPC Mesoanalysis and model soundings show around
1500-3000 J/kg of MLCAPE, 800-1200 J/kg of DCAPE, steep low-
level lapse rates, and around 20-30 knots of background flow in
the low to mid levels, which are all favorable for producing
strong winds. With progressive storm motions and lower
precipitable water values than preceding days, storms today
aren`t expected to pose a risk for flash flooding.

Any thunderstorm activity should wind down this evening,
resulting in dry conditions during the second half of the
overnight. A cold front will move through late tonight, causing
winds to turn light out of the north. Overnight lows are
forecast to be in the upper 60s to low 70s.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
The aforementioned front will stall out over the area tomorrow.
This will allow 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
tomorrow 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 tomorrow. 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.

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 /19Z THURSDAY THROUGH TUESDAY/...
Prevailing 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
thunderstorms is expected to remain low today, so have
maintained PROB30s in the TAFs. Coverage of storms is largely
expected to remain low tomorrow 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 today may gust to around 20 knots out of the southwest this
afternoon, before decreasing this evening. Winds should stay
light and gradually veer around from southwest to northwest to
northeast later tonight into tomorrow morning. Winds will remain
light tomorrow, 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...
Sporadic gusts to low-end SCA levels within southwesterly flow will
remain possible through the remainder of the afternoon. SMWs may
potentially be needed late this afternoon into this evening if
any thunderstorms move over the waters. 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 tomorrow.
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 tomorrow morning. Otherwise, the threat for tidal
flooding appears low.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory until 8 PM EDT this evening for DCZ001.
MD...Small Craft Advisory until 6 PM EDT this evening for MDZ008.
     Heat Advisory until 8 PM EDT this evening for MDZ003>006-008-
     011-013-014-016>018-503>508.
VA...Heat Advisory until 8 PM EDT this evening for VAZ028-030-031-
     053>055-057-501-502-505-506-526-527.
WV...Heat Advisory until 8 PM EDT this evening for WVZ051>053.
MARINE...Small Craft Advisory until 6 PM EDT this evening for
     ANZ530>543.
     Heat Advisory until 8 PM EDT this evening for ANZ530.

&&

$$

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