McLean, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

257
FXUS61 KLWX 301930
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
330 PM EDT Sun Mar 30 2025

.SYNOPSIS...
Low pressure will track into the Great Lakes tonight, and then
across southern Canada tomorrow, with a trailing cold front
moving through the area tomorrow night. High pressure will build
to our north for Tuesday and Wednesday, before another strong
area of low pressure tracks into the western Great Lakes on
Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
After ample sunshine this morning, clouds are on the increase
again as a weak disturbance aloft approaches from the west. The
aforementioned sunshine has allowed temperatures to climb into
the upper 70s and lower 80s across much of the area. The primary
exception to this is across northeast Maryland, where winds
remain easterly in association with a backdoor front that passed
through last night. There, temperatures will only make it into
the lower to middle 70s. This backdoor boundary will eventually
lift northward again later this afternoon into this evening.

Current (as of 3 PM) radar imagery shows showers overspreading
much of the West Virginia Panhandle and western Maryland. These
showers will continue to lift northeastward across the northern
Shenandoah Valley toward north central Maryland over the next
few hours. These showers could potentially reach the
northwestern DC suburbs and then eventually northeast Maryland
during the late afternoon/early evening hours, but questions
remain as to how well these showers will hold together as they
move into a relatively dry airmass at low-levels further east.
It also isn`t entirely out of the question that a thunderstorm
could briefly occur across north central Maryland (as advertised
by the 12z 3 km NAM and WRF-ARW), where some models show very
limited instability developing, as well as a bit of additional
low-level convergence along the retreating backdoor front.
Elsewhere, dry conditions are expected through the evening. This
initial round of showers should clear the area by around 9 or 10
PM, with dry conditions expected areawide for the first half of
the night. The bulk of the forecast area should experience dry
conditions through the second half of the night as well, but
decaying showers and thunderstorms from the Ohio Valley may
reach the Allegheny Front just prior to daybreak. Southerly
winds and clouds will keep temperatures very warm overnight,
with lows in the 60s for most (50s mountains).

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
A potent shortwave and its associated strong area of low
pressure will continue to lift northeastward across Ontario and
Quebec tomorrow, while a trailing shortwave tracks from OK/AR
tomorrow morning toward the central Appalachians tomorrow
evening. A trailing cold front will extend southwestward from
the low over southern Canada, and track across the forecast area
from west to east during the first half of tomorrow night.

While some questions remain regarding how well decaying
convection from today`s storms in the Ohio Valley will hold
together, model guidance is in reasonably good agreement that
appreciable daytime heating should ensue late tomorrow morning
into early tomorrow afternoon. As a result, surface based
instability will develop, and storms are expected to form by
early- mid afternoon along a pre-frontal trough. There is still
a bit of spread regarding exactly where this pre-frontal trough
will set up, but most guidance has it oriented from southwest
to northeast, somewhere across central or western portions of
the forecast area. Environmentally speaking, most models show
around 500-1000 J/kg of MLCAPE, within what will be a well
sheared environment (around 40-50 knots of effective bulk
shear). Initially, a mixture of short line segments and
supercells may be possible, before upscale growth causes
activity to turn predominantly linear in nature. The primary
hazard should be damaging winds, but a few instances of large
hail or a tornado can`t be completely ruled out. SPC currently
has the bulk of the forecast area outlooked in a Slight Risk for
severe thunderstorms, with an Enhanced Risk clipping Central
Virginia.

Storms should initially develop around mid- afternoon
across central and western portions of the forecast area. Storm
motions will be off toward the north and east, but the zone
where storms are developing will gradually shift to the south
and east, reaching the I-95 corridor during the late afternoon
and evening hours. Storms will linger through the evening along
and southeast of I-95, before finally clearing southern Maryland
around or just after midnight as the system`s cold front moves
through. Northwesterly winds, falling temperatures, and dry
conditions are expected during the second half of the night.
Overnight lows are forecast to be in the 40s for most, with 30s
in the mountains.

Sunny skies and a north to northwesterly breeze is expected on
Tuesday as high pressure builds to our north. High temperatures
are forecast to reach into the upper 50s to mid 60s for most,
with upper 40s in the mountains.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Ridging will build over the East during the middle and second half
of the week leading to a warming trend with 80s expected again.
Moisture return will be underway Wed afternoon into Thu. Light
showers will be possible Wed night into Thu in the return flow
particularly in western areas, but are more likely Fri into Sat when
cdfnt will be moving slowly across the area and area gets into the
cool sector and multiple waves of low pressure move along stalled
frontal zone. After temps in the 80s Thu and Fri, expect temps to
cool down significantly for Sat and Sun and the following week.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
VFR conditions and south to southwesterly winds gusting to
around 20-25 knots are expected today. Winds are currently
easterly at BWI and MTN, but should become south to
southwesterly by mid-late afternoon as a backdoor front retreats
to the north. Showers over the WV Panhandle and western MD will
spread north and east over the next few hours. PROB30s were
introduced at IAD, BWI, and MTN to account for the potential of
a brief shower later this afternoon. MRB will likely see on and
off showers for a few hours this afternoon, and has prevailing
-SHRA as a result.

VFR conditions continue tonight, with LLWS possible for a few
hours, especially at BWI and MTN. MVFR ceilings will be
possible for a few hours late tonight/early tomorrow morning,
before conditions return to VFR tomorrow morning. There`s a
slight chance for a shower late tonight/early tomorrow morning
as decaying activity moves in from the west, but chances are too
low to mention in the TAF at this time. Better chances for
showers and thunderstorms will move into the area late tomorrow
afternoon into tomorrow evening as a cold front approaches from
the northwest. Some of these storms may be strong to severe.
Outside of thunderstorms, winds will be out of the south
tomorrow. Showers and thunderstorms depart off to the east by
around midnight, with VFR conditions during the second half of
the night. Winds will shift to out of the northwest behind the
system`s cold front during the second half of the night. VFR
conditions and northwest to northerly flow are expected on
Tuesday.

Gusty SW winds of 25 to 35 kt will be possible Wed and Thu. Lots of
clouds both days, but no cig restrictions are expected.

&&

.MARINE...
SCA conditions are likely on and off through the day tomorrow
within southerly flow. Thunderstorms appear likely tomorrow
afternoon into tomorrow evening, with SMWs likely needed during
that time. Winds turn northwesterly behind a cold front during
the second half of tomorrow night, and remain north to
northwesterly during the day Tuesday, with SCA level gusts
lingering through Tuesday morning.

SCA conditions likely Wednesday through Friday.

&&

.TIDES/COASTAL FLOODING...
Sensitive tidal locations such as Baltimore, Annapolis, and Havre De
Grace may reach Action stage as a strong cold front approaches the
waters. Strong southerly flow will lead to increased tidal anomalies
ahead of the frontal passage, with anomalies peaking on Monday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until noon EDT Tuesday for MDZ008.
VA...None.
WV...None.
MARINE...Small Craft Advisory until noon EDT Tuesday for ANZ530>543.

&&

$$

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