Arlington, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

297
FXUS61 KLWX 171514
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1114 AM EDT Mon Aug 17 2026

.WHAT HAS CHANGED...
Only minor changes needed to account for current conditions,
including a few showers affecting the Allegheny Mountains this
morning. Updated rain chances and aviation forecasts this
afternoon/evening based on incoming computer models.

&&

.KEY MESSAGES...
- 1) A few showers and thunderstorms remain possible until a
  cold front crosses later today.

- 2) Thunderstorm chances return Wednesday night into Thursday,
  and continue into next weekend.

&&

.DISCUSSION...
KEY MESSAGE 1...A few showers and thunderstorms remain possible
until a cold front crosses later today.

Radar as of 1015Z/615AM EDT shows scattered shower activity near
and west of the Allegheny Front.

A couple of convectively-augmented shortwaves remain across the
southern Ohio Valley and Coalfields. These waves would cross
the region this afternoon, along with some right- entrance
ascent from a 70-knot upper jet streak roughly near the PA/NY
border. A lack of low-level convergence due to mostly
unidirectional light northwest flow should keep convective
coverage low, despite the mid/upper waves at a favorable time.
Steepened low-level lapse rates with lingering low-level
moisture could result in a few gusty thunderstorms (35-50 mph
perhaps), along with some downpours and lightning. Heating and
instability will be a bit more pronounced across central VA, so
areas generally along the I-64 corridor would probably stand the
highest chance at seeing anything at or near severe thresholds
(which is 58 mph). DCAPE will be very marginal (400-600 J/kg)
due to lingering mid- level moisture and meager lapse rates
aloft. Typically, values of at least 600-800 J/kg are needed to
accelerate downdraft winds to severe levels.

The low-level synoptic cold front, currently from near Detroit
to Indianapolis, will cross the region tonight. A bit of an
increase in low-level convergence on the tail of the mid/upper
waves, as well as a theta-e ridge could cause a bit of an uptick
in activity a little later than usual (6-10pm). Overall modest
thermodynamics and increasing nocturnal stability coupled with
disjointed forcing should keep any strong to severe threat low,
though some lightning strikes and downpours are still possible.

If any of the upstream waves trend a bit stronger, and/or CAPE
verifies a bit higher than currently progged, then perhaps a
couple more stronger storms would be possible through this
evening. Otherwise, activity should dwindle overnight as the
front swings through.


KEY MESSAGE 2...Thunderstorm chances return Wednesday night into
Thursday, and continue into next weekend.

With a cold front drifting south of our region on Thursday, shower
and thunderstorm chances return through next weekend. The best
chance for activity occurring is on Thursday. At this time,
it`s not certain if there will be enough instability, or enough
overlap with higher shear values, to present a severe weather
threat. It`s possible the front will stall or only move just
south of the area, which will play a role in precipitation
chances Friday. After the frontal passage and heading into the
weekend, we could see a slight cool down Friday though Sunday
with highs in the 70s and 80s.

On Saturday, a shortwave trough may cause low pressure to develop
along the front, which could bring more rain, even if we are north
of its track. The next cold front could approach from the Great
Lakes next Sunday. Temperatures may fluctuate a little depending on
what side of the front we`re on, but likely fall some by next
weekend, assuming the front pushes to the southeast.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Mainly VFR with lowering precip chances through tonight. Widely
scattered TS possible this afternoon/evening. Incoming 12Z
computer models are a bit more consistent on timing and
coverage, so added PROB30 groups with 15Z amendments. NW flow
7-12 kts is expected, perhaps becoming briefly a bit more W this
evening before shifting to N by daybreak Tue. IFR CIGs/fog
possible especially near MRB/CHO after 06Z tonight.

VFR with return to S flow Wednesday, then potential showers and
thunderstorms re-enter the forecast through Friday.

&&

.MARINE...
Generally light winds are expected through the upcoming week. A
brief period of marginal SCA southerly channeling is possible
Wednesday evening. Otherwise, NW winds today briefly shift to W
this evening, then N Tuesday before returning to S Wednesday. A
few thunderstorms are possible and may prompt a couple Special
Marine Warnings this afternoon and evening. A cold front may
bring additional thunderstorms Thursday into Friday.

&&

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

&&

$$

DISCUSSION...ADS/DHOF/KJP/KVH
AVIATION...ADS/DHOF/KJP/KVH
MARINE...ADS/DHOF/KJP/KVH