Reston, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

109
FXUS61 KLWX 120127 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
927 PM EDT Mon Aug 11 2025

.SYNOPSIS...
High pressure initially over the Mid-Atlantic gradually slides
out to sea by Tuesday. As this occurs, heat and humidity will
increase which also comes with increasing thunderstorm chances.
A slow moving frontal zone approaches from the west by mid-week.
This system eventually stalls nearby from Thursday into the
first half of the weekend. This maintains a summertime pattern
late in the work week and into the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...

Mostly clear at this time, but model guidance show stratus layer
forming across central VA late tonight/early Tue morning. Milder
than recent nights due to higher dewpoints.

Previous afd...

For tonight, conditions will certainly be milder than the
previous week. Forecast lows are expected to be in the upper 60s
to low 70s, while higher elevations should see low/mid 60s. Like
preceding nights, low-level moisture getting trapped underneath
forming radiation inversions could aid in some patchy fog
development. Expect a bulk of the area to see some of this fog,
becoming locally denser in the favored low-lying valley
locations.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
High pressure initially over the region is forecast to slowly
slide offshore into Tuesday. This allows further intrusion of
Gulf moisture along with increasing temperatures. Broadly
speaking, forecast highs will rise into the upper 80s to low 90s
each day which yields heat indices into the mid/upper 90s. A
few of the more humid spots could see such heat indices near the
century mark closer to the Chesapeake Bay. As usual, mountain
locales will expect this return of the heat as highs are
confined to the 70s to low 80s. Mild nights also are favored as
the I-95 corridor remains in the low 70s (perhaps mid 70s inside
D.C. and Baltimore). For the Blue Ridge westward, most should
see lows in the mid 60s, slightly cooler over the mountain tops.

Regarding convective chances, Tuesday should yield an uptick in
activity for areas west of U.S. 15. Based on the 12Z high-
resolution model suite, developing storms should be isolated to
scattered in nature. A further expansion of storms is likely by
Wednesday as a slow moving cold front approaches from the Lower
Great Lakes. While a brunt of the height falls stay north of the
international border with Canada, some weak forcing could graze
the Mid-Atlantic states. The atmosphere should be rather
unstable with mixed-layer CAPE values of around 2,000 J/kg, but
with weaker vertical shear profiles. Thus, any severe aspect of
these storms should be somewhat limited and more focused on
convection with stronger downburst potential. With precipitable
water values near 2 inches, some flash flooding threat will
exist. It is too early to tell where this focus would set up as
it is still over 48 hours away.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
A summertime pattern persists through the period with heat,
humidity, and daily chances for showers and thunderstorms in the
forecast. On Thursday, a rather potent longwave trough crosses
through Quebec while the attendant height falls graze the
northeastern U.S. In the wake, global ensembles show a subtropical
ridge across the southeastern U.S. strengthening and expanding in
time. 500-mb heights push back into the 589-592 dm range as the
influence of northern stream disturbances wanes. While the initial
longwave trough carries a cold front on the doorstep of the local
area, the boundary should stall nearby on Friday before completely
shearing out over the weekend.

Daily high temperatures should push into the mid 80s to low 90s,
with mountain locales seeing mainly 70s to low 80s. Given the return
of the humidity, overnight lows will not plunge the way they have
been over the past week or so. Expect most to fall into the upper
60s to low 70s, with some low/mid 60s across the mountains. The best
chance for showers and thunderstorms would be Thursday and Friday
with the cold front stalling nearby. Thereafter, the further
building of heights and lack of any frontal zones leads to
decreasing convective chances for the weekend. However, in these
scenarios, mesoscale boundaries like bay/river breezes and terrain
circulations can act as a focus for some afternoon/evening
convection.

By next Monday, models show another round of amplified flow
tracking across the northern tier of the nation. This helps
drive an additional cold front across the Great Lakes and Ohio
Valley. Further storm chances are possible in this environment.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Heading into tonight, a broader area of patchy fog is expected
which favors IFR to MVFR visibility between 4 AM and 9 AM
Tuesday. Daytime heating should quickly mix out any fog with a
return to VFR conditions likely by mid/late morning.

Convective chances increase the following couple of days,
especially by Wednesday as the next cold front approaches from
the Great Lakes. Periods of restrictions are possible as storms
become more widespread and stronger in nature. Any severe aspect
is unknown at this time. Overall wind fields through Wednesday
will mainly be southerly before shifting to southwesterly ahead
of the next front.

With a frontal zone nearby, there will be a risk of daily
afternoon/evening showers and thunderstorms Thu/Fri. Thus, some
restrictions cannot be ruled out at times across all terminals.
Gradients remain on the weaker side with mainly northwesterly
winds for Thursday before turning more east to southeasterly by
Friday into Saturday. However, such winds will largely be
dependent on the position of the front and other convective
processes. This boundary meanders nearby over the weekend.

&&

.MARINE...
Gradients remain on the weaker side today as high pressure stays
over the area. This anticyclone center gradually pulls away
offshore on Tuesday. In the wake, an uptick in southerly winds
could lead to some channeling effects on Tuesday evening. This
could near Small Craft Advisory levels. Southerly gusts then
drop to around 10 to 15 knots into Wednesday. The primary
convective chances would be on Wednesday as a slow moving cold
front approaches from the Great Lakes. Any stronger storm could
require a Special Marine Warning or two.

While background wind fields should mainly keep gusts around 10
knots or less on Thursday and Friday, the risk of afternoon/evening
convection may bring hazardous conditions to the waters. Initial
winds will be out of the northwest before turning more light and
variable into Friday.

&&

.TIDES/COASTAL FLOODING...
Elevated tidal anomalies look to continue through Tuesday given
the recent full moon and light winds. While minor tidal flooding
is not expected, some cycles could go into Action stage during
the high astronomical tides (especially at Annapolis and
perhaps Dahlgren/Alexandria).

&&

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

&&

$$

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