Reston, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

188
FXUS61 KLWX 201428 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
1028 AM EDT Sun Jul 20 2025

.SYNOPSIS...
A cold front moves through the area tonight. Less humidity and drier
conditions to start the week as Canadian high pressure builds
in to the north. As this ridge of high pressure moves into the
Canadian Maritimes, heat and humidity return late in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...

Sfc winds have shifted to the W at IAD and BWI behind a sfc
trof preceding a cold front still situated across the eastern
Great Lks. The strengthening W to WNW winds should begin to
scour out the low-level moisture later today. The low-level
westerlies will limit sfc covergence and this coupled with the
decreasing moisture content should result in limited convection.
00Z HREF data suggest limited convection today with the best
chances over Cecil County, far southern MD, the MD Eastern
Shore, and Highland County VA. Any development should be late,
mainly in the 6 PM - 9 PM time frame. Still hot today with heat
indices close to 100.

Previous afd...

One final hot and humid day before the pattern breaks for the
start of the week. Highs reach the upper 80s to low 90s this
afternoon, with heat indices in the low 100s east of the Blue
Ridge and upper 90s to the west. We should fall just below Heat
Advisory criteria.

Ahead of the main cold front that slides through tonight, there will
be some coverage of showers and maybe a few thunderstorms this
afternoon. This is  most likely along and north of the Potomac,
especially in north to northeast MD closer to the stalled boundary.
While SPC has maintained a Marginal Risk (level 1 of 5) for severe
storms today, the overall threat for the area is conditional. Most
of the area should be okay, though if a storm does get going there
will be enough shear/instability for it to become severe. The main
threat from any severe storm will be damaging wind gusts.

Most of the convection outside of the Alleghenies comes to an end
late this afternoon. The cold front starts to move in this evening
into tonight, with models fairly confidence the front will make
quick progression east of the Blue Ridge. However, the backside of
the front from the Central Appalachians to the central
Shenandoah Valley will be slower to move, and models continue to
show showers in those areas tonight. The drier air won`t arrive
until Monday morning, so much of a temp/humidity change tonight
as lows settle in the upper 60s to low 70s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
The cold front crosses most of the area by sunrise Monday, though a
portion of the front along the Central Alleghenies likely stalls
somewhere across southern WV into southwest VA. Most of the area is
going to be dry on Monday, with much lower humidity. However,
scattered showers and thunderstorms could fire along the frontal
boundary around the I-64/I-81 corridor and points south/west. Highs
Monday only reach the low to mid 80s.

A full FROPA occurs Monday night as a reinforcing trough crosses the
area. Dry for Tuesday as highs only reach the low 80s, with dew
points dropping to the 50s to low 60s. Overnight lows to start the
week will be in the 60s, with upper 50s possible in some spots.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
High pressure will shift eastward off the New England coastline on
Wednesday. Winds will gradually shift from easterly to southerly
over the course of the day, which may lead to a slight uptick in
humidity, with dewpoints climbing back into the lower 60s. Skies
should remain mostly sunny, and temperatures will remain below
normal, with highs in the low to mid 80s.

High pressure will progress further offshore late in the week as
upper ridging builds in aloft from the Ohio Valley. Winds will
remain southerly as the the high shifts further offshore, which will
lead to a return of the heat and humidity.  Dewpoints will climb
well into the 60s on Thursday, before returning into the 70s on
Friday. Temperatures will be on the increase as well, with highs on
Thursday in the low to mid 90s, and then mid to potentially even
upper 90s by Friday. With the upper ridge building in from the west,
shower and thunderstorm activity is expected to remain limited, or
potentially even non-existent on Thursday. Coverage of storms is
expected to remain low on Friday as well, but with likely at least a
few storms around as the upper level ridge starts to weaken
slightly.

By Saturday, the upper ridge breaks down even further as a weak
frontal boundary drops through the region. The continue hot/humid
conditions, paired with even a weak disturbance, could result in
some afternoon thunderstorms.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
VFR conditions are expected to persist today. Coverage of
afternoon showers and thunderstorms is expected to be much
lower, and not enough to include in the TAFs at this time. A
cold front moves through tonight and brings VFR conditions for
the start of the week.

VFR conditions are expected on both Wednesday and Thursday. Winds
will start out easterly on Wednesday, before turning out of the
south by the end of the day and remaining out of the south through
Thursday.

&&

.MARINE...
A cold front is forecast to move across the area late tonight.
Ahead of the front a few thunderstorms are possible over the
waters, though coverage is expected to be low. Winds turn
northerly behind the front, with SCA conditions developing over
the Chesapeake Bay south of the Bay Bridge, and lower Tidal
Potomac.

Winds drop below SCA levels Monday morning, with another brief surge
possible late Monday night. Otherwise, favorable marine conditions
with winds staying below SCA levels Tuesday.

Winds will turn out of the southeast on Wednesday as high pressure
pushes offshore, but should remain sub-SCA criteria. By Thursday,
winds pick up a few knots and turn southerly. Sub-SCA winds expected
during the day, but could see southerly channeling during the
evening hours that could approach SCA criteria.

&&

.TIDES/COASTAL FLOODING...
Light winds across the area will maintain elevated tidal anomalies.
At this point, only Annapolis could see a run at Minor tidal
flooding, mainly during the higher of the astronomical tides. These
will occur during the middle of the night this weekend. A strong
cold front moves through the waters late tonight, which should help
lower water levels for the start of the week.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 3 AM to noon EDT Monday for
     ANZ532>534-537-540-541-543.

&&

$$

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