Arlington, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

313
FXUS61 KLWX 171017
AFDLWX

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

.WHAT HAS CHANGED...
Small Craft Advisories have expired. Aside from a few showers
along and west of the Alleghenies, rain has relented for the
time being.

&&

.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 are evident as of
early this morning over the OH Valley. One such wave was near
the IL/IN/KY intersection producing widespread thunderstorms.
A second, smaller wave was over the east-central IN/west-
central OH border vicinity with more sporadic convection. 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 /12Z MONDAY THROUGH FRIDAY/...
Mainly VFR with lowering precip chances through tonight. Widely
scattered TS possible this afternoon/evening, but sparse
coverage keeps confidence too low to include in the TAF at the
moment. 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...DHOF/KJP/KVH
AVIATION...DHOF/KJP/KVH
MARINE...DHOF/KJP/KVH