McLean, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

243
FXUS61 KLWX 030140
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
840 PM EST Sun Feb 2 2025

.SYNOPSIS...
Cooler temperatures and abundant cloud cover for the remainder of
today as high pressure pushes off the northern New England coast and
a warm front lifts in from the Ohio River Valley. The warm front
will cross the region tonight bringing a brief wintry mix to the
Allegheny and Catoctin Mountains. Warming temperatures and sunshine
return briefly Monday with a cold frontal passage Monday night into
Tuesday. The front will stall to the south by the middle of the
week, allowing for a series of low pressure systems to cross the
region.

&&

.NEAR TERM /THROUGH TONIGHT/...
EVENING UPDATE: Any precipitation has largely come to an and
this evening, though most radar echoes that did show up really
struggle to produce any precipitation at the ground. Temps have
been pretty steady in the 33 to 36 range across much of the
region, and that will continue for much of the overnight hours.
Low temperatures will be in the 30s across the area, only
dropping maybe a degree or two from what is being observed
currently. There is a slight chance of light rain showers
overnight in the Alleghenies with dry conditions elsewhere.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As the parent low continues pushing eastward into Northern Canada,
the associated warm front will continue pushing northward into New
England. The associated cold front will approach from the west,
set to move through the forecast area Monday night into Tuesday.
Temperatures on Monday rise well above normal in the wake of the
warm frontal passage with high temperatures on Monday nearing
or exceeding 60. Those at higher elevations will stay in the low
50s.

Dry conditions are expected through Monday evening. The
aforementioned cold front moves through the forecast area Monday
night, bringing a slight chance to chance of rain showers for
those along the Alleghenies. Overnight low temperatures will be
in the 40s for most, with those at higher elevations staying in
the mid to upper 30s. Therefore, any precipitation will likely
stay as rain. The rest of the area is expected to stay dry
through Tuesday.

High temperatures on Tuesday will widely vary depending on the
timing of the cold front. High temperatures in the Alleghenies
will be in the upper 30s to low 40s in the wake of the frontal
passage while highs in the mid 60s are expected in central
Virginia ahead of the frontal passage. In the wake of the cold
front, overnight low temperatures dip below freezing for the
northern half of the forecast area. The southern portions of the
area will dip into the mid to upper 30s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Zonal flow will continue across the CONUS for the middle and latter
half of the workweek. As a result, the forecast pattern will remain
unsettled with large temperature swings as the area sits between a
colder airmass to the north and warmer one to the south. This sharp
baroclinic zone will lead to a rather unsettled period of weather
with increased cloud cover and precipitation chances Wednesday into
the upcoming weekend.

The bulk of the precipitation through the extended period will
mainly be in the form of rain. A few exceptions to this will be
Wednesday into Wednesday night and again Saturday into Saturday
night where cold air damming could lead to overrunning across
portions of the region. The highest confidence for frozen
precipitation within these aforementioned timeframe look to be in
areas along and north of I-66/US-50. This is where shallow cold air
may be more readily available compared to areas further south.

Shortwave ridging will move into the area Wednesday with 1028-1032
mb high pressure locked up across southeast Canada/eastern Great
Lakes region. Meanwhile, low level warm air advection combined with
a shortwave pressure trough and approaching warm front from the
central Appalachians will lead to added lift for light precipitation
to occur. With the surface high to the north, a steady supply of
shallow cold air will be allowed to drain south along the eastern
face of the Appalachians. One question that remains is how quickly
the column saturates, which will dictate how quickly precipitation
will occur. This will also aid in potential precipitation type.
Right now, 12z guidance continues show light wintry precipitation in
the form of sleet and freezing rain mainly from I-66/US-50 northward
the PA/MD line. Overall duration of precip has yet to be determined
with a focus toward late Wednesday morning into the evening hours
ahead of warmer air set to move in Wednesday night into early
Thursday morning. Accumulations of ice have yet to be determined.
Models have come into the better agreement with 50-80 percent probs
of at least 0.01" of freezing rain per the NBM, GEFS,and EPS. These
values drop below 30 percent for amounts up to 0.10". Either way
travel disruptions are possible if this threat materializes
Wednesday into early Thursday morning especially in locations north
of I-66/US-50.

Rain is likely Thursday as another wave of low pressure moves
overhead. At this point, the bulk of the region will enter the warm
sector as the warm front responsible for the overrunning wintry
precip Wednesday lifts into New England. Highs Thursday will climb
into the upper 50s and low 60s. Locations south of Washington DC
could make a run at 65 degrees. This of course will occur if
precipitation can exit and skies can clear. Highest confidence for
temperatures above 65 degrees look to be across central VA
especially along and south of I-64.

Weak high pressure builds back into the area Friday before another
area of low pressure and front approach from the Tennessee River
Valley/central Appalachians this weekend. This storm system could
bring renewed wintry precipitation concerns to the area depending on
the track and placement of the high to the north which may deliver
another shallow cold air wedge to the region. Temperatures will cool
back into the 40s for highs Friday and Saturday with lows in the
30s.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
EVENING UPDATE: VFR to MVFR conditions are expected across all
terminals overnight with overcast ceilings 5-8kft being
currently observed and light southerly winds.

PREVIOUS DISCUSSION: South/southwest winds with VFR conditions
are expected Monday. Winds gust 10 to 15 knots in the afternoon.
LLWS is possible overnight Monday into Tuesday at all terminals
with confidence remaining too low to include in the TAF. On
Tuesday, winds shift to northwesterly, gusting 15 to 25 knots in
the afternoon. Winds diminish overnight while shifting to
northeasterly.

Sub-VFR conditions (MVFR to IFR cigs) return with periods of rain
Wednesday into Thursday. Some icing is possible mainly north of the
of I-66/US-50 (i.e KMRB, KHGR, KBWI, KIAD, KMTN, and KHGR)
especially Wednesday morning into midday. This will be reevaluated
in upcoming forecast packages. Easterly winds Wednesday turn
southeasterly Wednesday afternoon into much of Thursday. Winds
remain light at 5-10 kts. Gusts to 15 to 20 kts during the
afternoons. VFR conditions slowly return Friday with additional sub-
VFR chances this weekend.

&&

.MARINE...
Winds remain out of the south overnight with patchy fog possible
over the southern portions of the Chesapeake Bay and lower
Potomac. Winds remain below SCA criteria through Monday morning.
Winds increase in the afternoon with Small Craft Advisories
possible Monday evening and into the overnight. As a cold front
moves across the waters, advisories are likely Tuesday.

Sub-SCA level winds are expected Wednesday. Easterly winds Wednesday
morning turn southeasterly late Wednesday into Thursday. SCA
conditions return Thursday into Friday as a wave of low pressure and
front cross the waters. Additional SCA conditions are possible
heading into the upcoming weekend.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$

SYNOPSIS...AVS
NEAR TERM...CJL
SHORT TERM...AVS
LONG TERM...EST
AVIATION...AVS/CJL/EST
MARINE...AVS/EST