McLean, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

723
FXUS61 KLWX 141509
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1109 AM EDT Sun Jun 14 2026

.WHAT HAS CHANGED...
Confidence in the timing of storms today is starting to
increase. See discussion below for details.

&&

.KEY MESSAGES...
- 1) Severe thunderstorms are expected later this afternoon
  into this evening.

- 2) A return to warm and humid conditions and the potential for
  strong to severe thunderstorms Thursday.

&&

.DISCUSSION...
KEY MESSAGE 1...Severe thunderstorms are expected later this
afternoon into this evening.

A closed mid-upper low continues to circulate well off to our north
this morning across northern portions of Ontario/Quebec in the
vicinity of James Bay. A well defined shortwave is evident on water
vapor imagery to the southwest of the closed upper low,
extending southwestward across Lake Superior into Minnesota,
Wisconsin, and Iowa. This disturbance will rotate through the
base of the broader trough over the course of the day today,
transitioning from a positive tilt currently to a neutral tilt
by this evening as it tracks through the Lower Great Lakes and
Ohio Valley. At the surface, an area of low pressure is located
just downstream of the upper low to the east of James Bay. An
occluded front extends southward across northern portions of
Quebec, before turning into a cold front further south. This
cold front then arcs southwestward across Lakes Ontario and
Erie, and then across Lower Michigan, Indiana and Illinois. As
the aforementioned shortwave progresses eastward, it will drive
the cold front further south and east. The cold front is
expected to reach the Allegheny Front around sunset, before
progressing southeastward through the remainder of the forecast
area overnight.

The 12z IAD sounding shows shallow moisture right near the
surface, with much drier air evident through the rest of the
low to mid levels of the atmosphere. The sounding had a
precipitable water value of just 1.05 inches, which reflects the
airmass that brought us dry conditions yesterday. A similar
thermodynamic profile is also seen in the 12z RNK, which much
like the IAD sounding shows an elevated mixed layer roughly in
the 800-600 hPa layer. The presence of this EML should act to
keep conditions capped locally through the early afternoon
hours. Other 12z soundings and SPC mesoanalysis show higher
moisture air in the 925-850 hPa layer to our southwest over the
Ohio and Tennessee Valleys. As the day progresses, the low-level
mass response ahead of the aforementioned shortwave will draw
deeper moisture northeastward into our forecast area within
south to southwesterly low-level flow. Thunderstorm development
is expected to ultimately occur as that deeper moisture surges
northeastward into our area during the mid to late afternoon
hours.

Model guidance suggests that a surface trough will develop across
the middle of the forecast area this afternoon (roughly in the
vicinity of the Blue Ridge). While a thunderstorm could pop up
anywhere this afternoon once the deeper moisture moves in, this
surface trough is expected to serve as the primary source of
low- level convergence to initiate storms, with the most robust
thunderstorm development expected to occur once the deeper
moisture moves overtop the surface trough.

As a result, the net expectation from all of this is for isolated
thunderstorms to develop off to our southwest during the early
afternoon hours and then spread northeastward through the mid-
late afternoon. Coverage of these storms will likely remain on
the lower side to the west of the Blue Ridge until they
encounter the better surface convergence in the vicinity of the
Blue Ridge during the late afternoon hours/early evening hours.
The storms will then progress eastward toward the I-95 corridor
during the evening hours, likely increasing in coverage as they
do so. A surge of higher theat-e air northward out of the
Tidewater region this evening may help to further invigorate
storms as they move east of I-95.

We`ll also have to monitor an additional area of storms that will
develop along the system`s surface cold front in the Ohio Valley.
These storms will likely reach northwestern portions of the forecast
area (western MD and the WV Panhandle) around dark. The
tendency should be for this activity to weaken after sunset as
it moves further south and east, but a lower-end threat for
thunderstorms could potentially linger until around a little
after midnight along the I-95 corridor.

The background environment will be characterized by around 500-1000
J/kg of MLCAPE to the west of the Blue Ridge, and 1000-2000 J/kg
further east. Shear will also be on the increase as mid- upper
level winds strengthen ahead of the approaching shortwave. As a
result, effective bulk shear values are forecast to increase to
around 35-45 knots. Several hours of strong daytime heating are
expected in advance of any storms, allowing temperatures to
climb into the low to mid 90s by peak heating, and low-level
lapse rates to become very steep (8-9 C/km plus). DCAPE values
are also forecast to increase to in excess of 1000 J/kg to the
east of the Blue Ridge. Such an environment will be very
favorable for production of damaging winds in any stronger
storms that develop. Hodographs are relatively long and straight
with little in the way of low-level shear, but there is a
some slight curvature noted near the surface. As a result, the
environment doesn`t appear to be overly favorable for the
development of tornadoes, but a tornado or two can`t be
completely ruled out, especially if storms interact with
locally backed winds in the vicinity of the bay breeze. Very
warm surface temps and poor mid-level lapse rates should limit
the hail threat somewhat, but an isolated instance or two can`t
be ruled out, given deep layer shear values that could
potentially support supercells. SPC currently has the entire
forecast area outlooked in a Slight Risk (level 2 of 5) for
severe thunderstorms, with damaging winds being the primary
threat. It should be noted that this is a higher end Slight Risk
for locations to the east of the Blue Ridge, with the 30
percent wind contour. Storms are expected to be rather
progressive today, so the threat for flooding is expected to
remain low. WPC has a Marginal Risk for excessive rainfall
outlooked to the east of the Blue Ridge.

As hinted at before, coverage of storms is expected to be much lower
to the west of the Blue Ridge, with the peak threat likely
occurring during the mid-late afternoon hours. To the east of
the Blue Ridge (including the DC/Baltimore metros), the coverage
of storms is expected to be greater, and the timing is expected
to be later. For the DC/Baltimore metros, the highest coverage
of storms is expected to occur in the 5-10 PM window, although a
stray storm can`t be completely ruled out before, and there
could be a lingering low-end threat for a shower or storm until
a little after midnight. The system`s cold front will move
through later tonight, bringing chances for storms to an end as
the cooler and drier airmass behind the front moves in.

Much cooler, drier, and less humid conditions are forecast for
Monday and Tuesday. Mostly sunny skies are expected with high
temperatures in the upper 70s to around 80, dewpoints in the upper
40s to 50s, and a northwesterly breeze.

KEY MESSAGE 2...A return to warm and humid conditions and the
potential for strong to severe thunderstorms Thursday.

After trending somewhat drier at the start of the week, upper level
moisture starts to move into the region on Wed, along with a
trend upwards in temp as hotter & more humid conditions begin to
take over. A stray shower or thunderstorm could develop later
in the day Tuesday through early Wed, mainly east of the Blue
Ridge, as a weak warm front slides northward from the Carolinas
into VA.

Beginning Thu, a strong surface low will push east past the
Great Lakes with a stemming cold front that will push across the
Northeast and Mid-Atlantic. This cold front could result in
multiple showers and thunderstorms throughout the region, with
some becoming severe. There is already a 30%-45% severe
prob noted in NCAR`s AI model, and a 15%-30% severe prob noted
in CSU`s ML model. Timing and exact hazards are still the
primary uncertainties being 5 days out, but early markers are
 showing an early widespread severe risk with this system.

This front will track towards the south by Fri, which could
result in a few lingering showers across the southern portions
of the region and along the central Chesapeake Bay. High
pressure moves into the region on Sat.

&&

.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
S`ly winds and VFR conditions are expected through this
afternoon. S`ly winds increase this afternoon, and may gust to
around 20-25 knots. Thunderstorms are expected to develop across
the area this afternoon/evening. Confidence is currently low on
timing at individual locations, so have maintained PROB30s.
TEMPOs or prevailing groups will likely be needed as we move
closer in time and confidence increases with respect to exact
timing. The threat for thunderstorms will gradually wind down
through the evening. Winds will shift to out of the NW behind a
cold front tonight. Gusts to around 20-25 knots may be possible
at times later tonight within NW`ly flow. VFR conditions and
lighter NW winds are expected on Mon.

VFR conditions mainly expected Tue through Wed night.  Winds
light becoming southeast 5 to 10 knots Tue. Winds south 5 to 10
knots Wed.

&&

.MARINE...
S`ly winds are expected over the waters today. SCAs are in
effect for all waters through this evening for all waters, and
tonight for southern waters. Thunderstorms will likely impact
the waters this afternoon/evening, with SMWs likely being
needed. Damaging winds will be the primary threat, but a stray
waterspout or instance of large hail can`t be ruled out. A cold
front will move over the waters tonight, shifting winds around
to out of the NW. Winds will remain out of the northwest on
Mon, but are expected to drop below SCA levels by mid- morning.

No marine hazards expected Tue through Wed night. Winds light
becoming SE 5 to 10 knots Tue. Winds south 5 to 10 knots Wed.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 6 AM EDT Monday for MDZ008.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ530>534-537-
     539>541-543.
     Small Craft Advisory until 11 PM EDT this evening for ANZ535-
     536-538-542.

&&

$$

DISCUSSION...KJP/CPB
AVIATION...CPB
MARINE...CPB