Arlington, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

293
FXUS61 KLWX 162026
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
426 PM EDT Sun Aug 16 2026

.WHAT HAS CHANGED...
We continue to monitor storms approaching from the west. Those
storms will pose a threat for damaging winds, and potentially a
tornado or two as they move through this evening. A targeted
Flood Watch may also be considered for the DC Metro.

&&

.KEY MESSAGES...
- 1) Severe weather and flash flooding are possible through
  tonight.

- 2) Thunderstorm chances return Wednesday night into Thursday.

&&

.DISCUSSION...
KEY MESSAGE 1...Severe weather and flash flooding are possible
through tonight.

Very active weather is expected over the next 12 hours, with
the threat for flash flooding, damaging wind gusts, and a few
tornadoes.

As of 330 PM, regional radar shows two developing MCSs across
western Pennsylvania and West Virginia, both with a history of
producing damaging winds. These MCSs are expected to continue
eastward into our area over the next few hours. Skies have
cleared out ahead of the storms, so strong daytime heating is
underway and conditions are destabilizing. MLCAPE values are
forecast to increase to around 1500-2000 J/kg ahead of the line,
with effective bulk shear increasing to around 30-35 knots. This
parameter space should allow these storms to continue across
much of the forecast area, leading to a threat for primarily
damaging winds. With around 30 knots of 0-3 km shear oriented
roughly perpendicular to the lines, a brief QLCS tornado also
can`t be ruled out. This threat could be locally maximized as
the line encounters a warm front oriented from north to south
extending from near Frederick to Fredericksburg. The storms
should tend to weaken later tonight as they move east of this
boundary into a lower instability airmass.

Storms are right on the doorstep of the Alleghenies at the
moment, and should press eastward toward the I-95 corridor by
around 8-10 PM. Additional storms are also in the process of
developing across central Indiana to north central Ohio. Some
recent CAM runs hint that those storms may develop into a
secondary line that would move through a couple hours after the
first round. There are also some hints of backbuilding,
especially in the DC Metro area between those rounds as low-
level flow picks up behind the first MCS, equaling or exceeding
winds higher up in the atmosphere. This results in Corfidi
upshear vectors near zero, suggesting that backbuilding and
localized training could be possible in the vicinity of the warm
front. Thermodynamically, the environment is extremely
favorable for heavy rainfall production, with precipitable water
values well in excess of 2 inches, and forecast to potentially
near 2.5 inches this evening. That coupled with MLCAPE values
around 1000 J/kg and deep warm cloud layers will make any storms
capable of producing very heavy instantaneous rainfall rates.
That coupled with the potential for multiple rounds of storms,
and/or training/backbuilding raises concerns for flash flooding
this evening. A Flood Watch remains in effect for Garrett
County, which had a flood event a few nights ago. Another Flood
Watch may be considered for the DC Metro shortly, given the
above conditions.

Storms are expected to clear the area by around 2 or 3 AM, with
dry conditions later tonight. Additional thunderstorms may be
possible tomorrow afternoon, but coverage of storms is expected
to be much lower, and the threat for both severe thunderstorms
and flash flooding is expected to be much lower, if not zero.


KEY MESSAGE 2...Thunderstorm chances return Wednesday night into
Thursday.

Surface high pressure will build from the Ohio Valley into the Mid
Atlantic Tuesday and Wednesday, providing dry conditions and
slightly lower humidity. Temperatures may cool off a few degrees
Tuesday but overall remain seasonable.

The next cold front will approach from the northwest Wednesday
night, perhaps bringing some showers and thunderstorms depending on
its timing. The front will slowly drift south through the area
Thursday, which will result in the greatest chance of showers and
thunderstorms. At this time, it`s not certain if there will be
enough instability, and 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. 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.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
MVFR ceilings remain in place to the east of the Blue Ridge this
afternoon, with VFR conditions further west. Ceilings should
gradually lift over the next several hours, eventually making it
back to VFR everywhere by late tonight. Besides the low
ceilings, thunderstorms will be the other concern. Regional
radar shows two large clusters of thunderstorms across WV and
western PA. These storms will track eastward this evening,
eventually impacting all terminals with at least one round
(potentially two or three) of heavy rainfall, gusty winds, and
frequent lightning. The most likely timing of these storms for
the DC/Baltimore terminals will be roughly between 730 PM and 1
AM. After the storms move out later tonight, prevailing VFR
conditions are expected through the day Tuesday. A brief
thunderstorm also can`t be ruled out Monday afternoon, but
coverage of storms is expected to be much less than today. Winds
will be out of the south today, northwest tomorrow, and then
north on Tuesday.

Prevailing VFR conditions are anticipated Tuesday through Wednesday
with high pressure. Potential showers and thunderstorms re-enter the
forecast Thursday and Friday.

&&

.MARINE...
SCAs will continue within southerly flow this afternoon into
tonight, with some drop off in winds likely over the Middle and
Upper Tidal Potomac after sunset. SMWs may also potentially be
needed as thunderstorms approach the waters later this evening.
Winds shift to out of the northwest tomorrow, and then north on
Tuesday, but are expected to remain sub-SCA level in magnitude.

North to northwest winds continue for Tuesday but likely remain
below SCA levels. As high pressure departs, winds turn southerly by
late Wednesday, and channeling may bring marginal SCA conditions
along the bay during the evening/overnight. A cold front may bring
some thunderstorms on Thursday as winds shift back to the north.

&&

.TIDES/COASTAL FLOODING...
Water levels continue to rise along the Bay within southerly
flow. A Coastal Flood Advisory has been issued for Annapolis for
the high tide cycle this evening. Havre de Grace and Baltimore
will also come very close to Minor Flood Stage. Water levels
will decrease tomorrow as winds shift to out of the northwest.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 6 AM EDT Monday for MDZ008.
     Coastal Flood Advisory from 7 PM this evening to midnight EDT
     tonight for MDZ014.
     Flood Watch until midnight EDT tonight for MDZ509-510.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ530>534-
     537>543.
     Small Craft Advisory until 8 PM EDT this evening for ANZ535-
     536.

&&

$$

DISCUSSION...ADS/KJP
AVIATION...ADS/KJP
MARINE...ADS/KJP