Arlington, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

110
FXUS61 KLWX 180807
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
407 AM EDT Fri Sep 18 2026

.WHAT HAS CHANGED...
Recent forecast guidance suggests that thunderstorms will
likely be confined to Central Virginia today.

&&

.KEY MESSAGES...
- 1) Shower and thunderstorm chances shift southward in the
  wake of a cold front today. Slightly cooler and drier
  conditions are forecast for Saturday, before shower and
  thunderstorm chances return on Sunday.

- 2) Daily chances for showers persist through much of next week,
  with temperatures likely falling below normal.

&&

.DISCUSSION...
KEY MESSAGE 1...Shower and thunderstorm chances shift southward
in the wake of a cold front today. Slightly cooler and drier
conditions are forecast for Saturday, before shower and
thunderstorm chances return on Sunday.

A cold front will move southward across the area this morning.
As winds shift to out of the north, slightly cooler and drier
air will gradually filter in from the north over the course of
the day. Dewpoints will drop from the lower 70s currently into
the 60s by later this afternoon, and temperatures will still
climb into the 80s at lower elevations beneath a mix of sun and
clouds. As the drier air advects in from the north, instability
will be confined to far southwestern portions of the forecast
area by peak heating this afternoon. As a result, any
thunderstorms are expected to form across Central Virginia
before eventually tracking off to the south and east out of our
forecast area. Forecast soundings show less than 1000 J/kg of
MLCAPE, DCAPE values of 600 J/kg or less, and relatively weak
wind fields, so any storms that form aren`t expected to turn
severe. A few showers may be possible further north, but
coverage of showers is expected to be isolated at best.

A secondary surge of cold/dry advection will occur tonight
within north to northeasterly flow as high pressure builds to
our north. Dry conditions are expected across the entire
forecast area on Saturday within the drier airmass. Temperatures
are forecast to climb into the 70s to near 80 beneath a mix of
sun and clouds.

High pressure will shift offshore on Sunday, causing winds to
turn back out of the south. In response, a warmer, more humid
airmass will work back in from the south and west over the
course of the day, with dewpoints climbing back into the lower
70s and temperatures reaching into the lower 80s. A deep upper
trough will track well to our north across Ontario and Quebec
during this time, with an unseasonably strong area of high
pressure building in the zone of subsidence in its wake across
Ontario. This anomalously strong high building to our northwest
will encourage a cold front to approach from the north. While
the front will likely remain off to our north during the
daylight hours, gradually falling heights aloft combined with
increasing heat/humidity at low-levels will likely lead to the
development of showers and a few thunderstorms Sunday afternoon.
Showers could then continue on and off through the night as the
cold front drops southward through the area.


KEY MESSAGE 2...Daily chances for showers persist through much
of next week, with temperatures likely falling below normal

A cold front drops through the forecast area on Sunday night
before stalling to the south, bringing daily chances for showers.
In addition to daily precipitation, a cooler airmass builds
overhead in the wake of the cold front, yielding cooling
temperatures each day. On Monday, high temperatures will be in
the 70s for most (60s mtns) with overnight lows in the 50s/60s.
By midweek, high temperatures will top out in the upper 50s to
60s with overnight lows in the 50s. These temperatures remain
somewhat uncertain with large model spread, but the forecast
favors the cooler side of guidance given a cold air damming
surface pattern. Overall, nearby disturbances bring unsettled
weather to the region persisting through midweek.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
Other than some patchy fog this morning, prevailing VFR
conditions are expected at the terminals through the day today.
A few MVFR clouds can`t be completely ruled out for a brief time late
this morning into early this afternoon, but for now have kept
just a mention of FEW030 in the TAFs. Winds today will be out of
the north, and may gust to around 15-20 knots. Winds remain out
of the north to northeast tonight as a secondary surge of cold
advection moves through. Most guidance keeps conditions VFR, but
a few solutions show some MVFR clouds later tonight through the
day Saturday. For now we`re favoring VFR conditions through that
period. Winds shift to out of the east by Saturday afternoon,
and then south on Sunday, with continued prevailing VFR
conditions. Temporary drops to sub-VFR conditions may be
possible in any thunderstorms that form Sunday afternoon, but
coverage of storms isn`t expected to be high.

Winds shift to north/northeasterly on Monday in the wake of the
front persisting through late next week. Showers are possible
each day, with restrictions expected during heaviest
precipitation. Gusts begin light and strengthen moderately as
the week continues.

&&

.MARINE...
Winds shift to out of the north today in the wake of a cold
front, but are expected to remain just below SCA levels. A
secondary surge of cold advection will move through tonight,
with winds potentially reaching low-end SCA levels for a time as
they shift to out of the north-northeast. Confidence was still
too low to issue an SCA at this time, but the potential will
need to monitored through the day. Winds gradually shift to out
of the east on Saturday, and then south on Sunday. Low-end SCA
conditions may be possible at times throughout the weekend
within both easterly and southerly flow. SMWs could also be
possible Sunday afternoon if thunderstorms track toward the
waters.

Winds shift to north/northeasterly on Monday in the wake of the
front persisting through late next week. After the weekend, gusts
could approach or surpass SCA criteria, potentially strengthening as
the week continues. While there`s still a lot of forecast
uncertainty at this juncture, some of the stronger solutions
show Gale force winds within east to northeasterly flow during
the middle of the week. Showers are possible each day, and SMWs
could be plausible, even if prevailing Gale conditions aren`t
realized.

&&

.TIDES/COASTAL FLOODING...
Water levels are forecast to drop behind a cold front within
northerly flow today through tonight. Anomalies start to climb
again Saturday into Sunday as winds turn to out of the east on
Saturday and then south on Sunday. Model guidance suggests
that Minor flooding may possible Saturday night into Sunday.
Water levels may drop again briefly on Monday as winds shift to
out of the northeast. Persistent east to northeasterly flow
during the middle of next week will likely lead to rising
anomalies and potential coastal flooding issues, although
uncertainty is high this far out, and it`s far too early to get
into details.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$

DISCUSSION...KJP/AVS/KVH
AVIATION...KJP/AVS/KVH
MARINE...KJP/AVS/KVH