McLean, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

214
FXUS61 KLWX 240842
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
342 AM EST Sun Nov 24 2024

.SYNOPSIS...
Decreasing winds and slightly warmer temperatures today as high
pressure briefly returns to the region. The warming trend looks to
continue into the start of the holiday workweek. A quick moving cold
front looks to cross the area Monday night into early Tuesday with
brief high pressure returning midweek. A complex low pressure system
tracking north and east from the Tennessee River Valley will bring
widespread precipitation and colder temperatures toward the
Thanksgiving holiday period.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface high pressure returns from the south today, centering itself
over the central and southern Appalachians region. Meanwhile, upper
level low pressure will continue to pull further away across the
Canadian Maritimes allowing for subtle height rises and a relaxing
low level jet under a flatter 500 mb flow pattern. With that said,
mid to high level clouds will likely linger through at least the
front half of the day especially in locations along and west of the
Blue Ridge under light upslope flow. Skies will trend mostly
to partly cloudy to start before clearing later in the
afternoon and evening hours as high pressure strengthens to the
south. 850 mb temperatures today will run +5 to +8 degrees C
which will yield highs in the mid to upper 50s across most
locations outside the mountains and directly along the PA/MD
line where the cloud cover will hang on the longest. A few
locations south of I-66/US-50 corridor could push into the low
60s due to a bit more sunshine compared to mid and high level
clouds. Winds will remain elevated this morning into mid-
afternoon with west to northwest gusts 15 to 25 mph. These
values will decrease later this afternoon and into the evening
as the gradient continues to relax.

Quiet conditions are expected tonight as high pressure over the
central/southern Appalachians pushes toward the southeast U.S coast.
With high pressure nearby, mostly clear skies look to prevail along
with lighter winds which will allow temperatures to fall into the
low to mid 30s. Sheltered valley locations should fall into the mid
to upper 20s, especially in areas west of the Alleghenies with the
added snowpack. Winds will turn southerly late with speeds less than
10 mph.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Dry conditions are expected for the first half of Monday ahead of
the next approaching low pressure system. The low and it`s
associated cold front are expected to cross the region late Monday
into early Tuesday morning. Deterministic and ensemble guidance
continue to show good agreement with increasing precipitation
chances along and west of the Alleghenies as early as late Monday
afternoon/early evening before spreading east toward the metros
Monday night. Rainfall amounts will remain fairly light with this
system with most of the area outside the Alleghenies receiving less
than a tenth of inch. Either way any precipitation that we do see
will continue to help with ongoing drought concerns.

High temperatures Monday will be well above average, reaching into
the low to mid 60s (50s in the mountains). Mostly sunny skies start
the day giving way to mostly cloudy skies by the late
afternoon/evening ahead of the approaching frontal boundary.

The cold front quickly exits the region Tuesday morning into Tuesday
midday allowing brief high pressure to build back over the region.
Overall, the 500 mb flow pattern will still remain fairly flat
across the area leading to not much of a change in airmass in the
wake of the departing front. High temperatures Tuesday will push
back into the mid to upper 50s and low 60s for most locations with
40s over the mountains. Post-frontal winds will turn to the west and
northwest with gusts 20 to 30 mph Tuesday morning into Tuesday
afternoon. Winds will decrease fairly quickly Tuesday night as high
pressure builds overhead. Lows Tuesday night will fall into the
upper 20s and low to mid 30s.


&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Subsidence behind the exiting upper trough and surface high pressure
building into the region is expected to yield dry conditions on
Wednesday.

While guidance continues to show a low developing over the central
Plains and tracking east to the Mid-Atlantic, the system has
trended warmer in recent runs. As a result, the current most
likely precip type looks to start as rain as the system moves
into the area Wednesday night into Thursday, only transitioning
to snow for the mountains in the upslope pattern behind the
system Friday into Saturday. However, there is still significant
spread in possible temperatures Thursday, so we shall continue
to monitor.

The system is expected to swiftly exit, with precipitation outside
of the mountains coming to an end Friday night. High pressure builds
into the southeast and looks to create a strong pressure gradient
across the area, resulting in strong gusty NW flow heading into the
weekend.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
VFR conditions are expected at most terminals through Wednesday.
Brief periods of MVFR cigs are possible through midday due to
residual mid and high level clouds especially in areas along and
west of the Blue Ridge.

West to northwest winds will continue to remain elevated through mid-
afternoon before decreasing later today as high pressure builds to
the south. Gusts of 15 to 20 kts are expected across all terminals
outside of KCHO/KSHD.

Sub-VFR conditions remain possible Monday night into Tuesday as a
quick moving cold front crosses the region. The front will bring
light to moderate showers to the terminals leading to some cig/vsby
restrictions during this time. The highest confidence for sub-VFR
will be at terminals west of the corridor (i.e KMRB, KHGR, and
KFDK). Winds will turn to the south Monday at 5 to 15 kts. Winds
increase late Monday night into Tuesday as the front passes. The
front quickly exits Tuesday morning into Tuesday midday allowing
conditions to improve. Post-frontal west to northwest winds will be
the biggest issue to aviation through sunset Tuesday with gusts of
20 to 30 kts expected. These values decrease Tuesday night into
Wednesday as high pressure builds overhead. No significant weather
is expected during this time.

Conditions may deteriorate Wednesday night into Thursday as a low
pressure system approaches. Precipitation with this system is
currently expected to be in the form of rain for the major
terminals, with snow restricted to the mountains. Winds increase out
of the NW behind the front Thursday night into Friday, with gusts 20-
25 kts possible.

&&

.MARINE...
Winds are slow to taper today with SCAs continuing across most of
the waters with gusts up to 20 kts through the early afternoon
period. Sub-SCA level winds are expected later this afternoon
through Monday as high pressure builds nearby.

Winds turn to the south on Monday as high pressure pushes offshore.
Some southerly channeling may be noted of the middle and open waters
of the Chesapeake Bay resulting in SCAs late Monday into Tuesday
ahead of an approaching cold front. The front may bring a line of
gusty showers across the waters late Monday night into early Tuesday
morning. SCAs will likely continue during this time although a few
gale force gusts are possible over the lower waters as the potential
line of showers push through.

Winds increase out of the west/northwest Tuesday morning into
Tuesday afternoon behind the front. SCA conditions are likely with
gusts upwards of 20 to 30 kts through at least sunset. SCAs could
continue into Tuesday night before dropping off Wednesday as high
pressure returns to the waters.

SCAs could continue into Wednesday morning before gradually
diminishing through the day as high pressure builds into the region.
Winds increase out of the south ahead of a cold front during the day
Thursday, then quickly shift W/NW behind it Thursday night into
Friday. Small Craft conditions are likely, and could approach Gale
criteria.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 1 PM EST this afternoon for MDZ008.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 1 PM EST this afternoon for
     ANZ530>534-538>543.
     Small Craft Advisory until 7 AM EST this morning for
     ANZ535>537.

&&

$$

SYNOPSIS...EST
NEAR TERM...EST
SHORT TERM...EST
LONG TERM...CAS
AVIATION...CAS/EST
MARINE...CAS/EST