Arlington, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

934
FXUS61 KLWX 201520
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1020 AM EST Tue Jan 20 2026

.WHAT HAS CHANGED...
Temperatures this morning have risen across portions of the
area, with the Cold Weather Advisory in the Blue Ridge and east
of the Allegheny front being cancelled. Cold Weather Advisories
and Extreme Cold Warnings remain in effect for the Alleghenies.
Confidence continues to increase for a significant winter storm
this weekend.

&&

.KEY MESSAGES...
- 1) Near-record cold this weekend, along with increasing
  potential for a significant winter storm.

- 2) Very cold conditions are expected over the region through
  tonight.

&&

.DISCUSSION...

KEY MESSAGE 1...Near-record cold this weekend, along with
increasing potential for a significant winter storm.

As mentioned above, a potent cold front pushes through the
region late Thursday into Friday, followed by a reinforcing
Arctic front late Friday into Saturday. This will lead to
increasingly cold conditions each day from Thursday through the
weekend. Well below average temperatures are forecast,
especially by Sunday. In addition, some upslope snow showers are
possible over the Alleghenies, with low but non-zero chances of
light precipitation further east on Friday. Extremely cold
temperatures are becoming likely Saturday night into next week,
with lows in the single digits and wind chills at or below zero.
Near-record low temperatures are possible during this time.

The upper-level pattern becomes quite active in both the northern
and southern branches of the jet stream heading into this
weekend. Models continue to be in generally good agreement
regarding the development of a low pressure system that tracks
across the southern U.S. A broad area of baroclinic/frontogenetic
forcing will develop along the interaction of an Arctic high to
the north and the deepening low. Ensemble guidance continues to
show an amplified southern stream influence - something we have
seen very little of so far this winter (typical of La Nina).
The surface low may not escape so easily out to sea given the
negative NAO block. The nearby steady source of very cold air
and the amplified southern stream occurring in tandem are what
raise some red flags for significant wintry precipitation
potential this weekend. Ample cold air will remain aloft and at
the surface with strong high pressure to the north and the
strong baroclinic zone to the south. As a result, the 01Z NBM
48-hour probability for at least 6 inches of snow (ending 12Z
Mon Jan 26) are at 40-70pct from NW to SE, and around 20-45pct
for 1 foot of snow from NW to SE. There are some noteworthy
probabilities for even higher amounts, as well, but uncertainty
still remains in regards to the exact track of the system which
could lead to a sharp QPF gradient on the north/northwest side
of the system possibly somewhere over our area.

The latest numerical model guidance continues to show
consistency in regards to the potential of this significant
weekend winter storm across the area. Trends for precipitation
onset time favor Saturday (most likely in the afternoon), with
the heaviest precipitation over the area then occurring through
Sunday afternoon. The last four runs of the ECMWF-AIFS
(deterministic) have shown a southward tick to the axis of
heaviest QPF, likely due in large part to a slower ejection of
shortwave energy out of the Southwest CONUS causing a slightly
flatter and more suppressed storm track. However, the 00Z
operational ECMWF (deterministic) as well as several members of
the EPS and EPS-AIFS (among a handful of members from other
ensembling systems) are also slower and more amplified with a
trailing northern stream wave dipping into the Rockies late in
the weekend; these two slower/deeper waves then phase as they
exit the Rockies and head for the Mississippi Valley. This
scenario results in a broad, flat area of low pressure the gets
caught underneath Arctic high pressure building over the
Northeast CONUS Saturday night, and drifts over the baroclinic
zone draped from the SW Atlantic into the Gulf. This low then
eventually gets absorbed into the deeper phasing trough
approaching from the west. This lifts the low pressure northward
up the coast causing precipitation to linger into Monday. It
should be noted that this is a relatively new shift, not yet
reflected in 01Z NBM progs that were used as a baseline to the
overnight forecast. Have not deviated from NBM and will instead
wait to see if there is some consistency in this outcome, or if
a more suppressed solution becomes more likely.

Depending on where the frontal zone is and where the area of low
pressure tracks, there could be significant wintry precipitation
this weekend over a large part of the South to Mid-Atlantic CONUS.
As noted, the potential is still there for that strong Arctic
high pressure to suppress the low pressure system to our south.
However, the strengthening upstream blocking pattern could
essentially put a floor on how far south the low will track.

Accumulating snow looks almost certain this weekend, with an
increasing likelihood of a warning-level event for much of the
region. But how exactly all of the moving pieces interact will
determine the difference between a moderately impactful snowfall
versus something much more significant.

It is important to monitor this threat closely this week as the
different parts of the system become better sampled by surface and
upper air observations. Stay tuned to weather.gov/lwx/winter
for the latest updates.



KEY MESSAGE 2...Very cold conditions are expected over the
region through tonight.

Temperatures this morning have risen across portions of the
area, with the Cold Weather Advisory in the Blue Ridge and east
of the Allegheny front being cancelled. Cold Weather Advisories
and Extreme Cold Warnings remain in effect for the Alleghenies.

It is a very cold and in many cases blustery start across the
Mid-Atlantic this morning with temperatures ranging from a few
degrees below zero over the peaks of the Appalachians to the
teens above zero for most of the lower elevations all the way to
the Chesapeake Bay.

Temperatures struggle to escape the 20s for much of the area
today (teens in the mountains) with perhaps only portions of
the central VA piedmont to southern MD poking above freezing for
a few hours in the afternoon. It will moderate but remain
colder than normal Wednesday ahead of another approaching front.
The main thing to really note on both days outside of the cold
temperatures is the very dry nature of the air mass. Some
guidance is hinting at RH values in the low teens this
afternoon, then in the 20s on Wednesday. With temperatures so
cold, we are not necessarily anticipating a wildfire threat, so
will not do an explicit Fire Weather discussion for now.
However, if this were a warmer day, it would be concerning.

Following the Wednesday front (which may bring a coating to a
few inches of snow over the Alleghenies), another front slides
across the region Thursday. This second front looks to come
through dry even in the mountains, but it will reinforce cold
temperatures across the region. A third front, which may be
accompanied by a wave of low pressure gliding by to the south,
swings by on Friday. Some ensemble members are a bit more
amplified with this little lead wave, enough so that the 01Z NBM
and 03Z SREF paint a few tenths of an inch of snow across the
region. Will monitor trends and update in future cycles as
needed, but for now just something to monitor ahead of a much
larger threat looming for the upcoming weekend.


&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
Winds will remain elevated with W/NW gusts to 20-25 knots. The
wind will diminish late afternoon into this evening becoming
light out of the southeast by daybreak as high pressure moves
overhead and then offshore. Very few clouds and no precip are
expected during this time.

VFR conditions will prevail through Wednesday across the
TAF sites. Winds will turn southerly ahead of the next front
Wednesday with gusts between 20 to 25 kts. The front will come
through dry with just a few upslope snow showers over the
mountains. An additional front will cross Thursday once again
leading to elevated winds across the terminals.

A lead wave of low pressure passing to the south as another
front crosses could bring a little spotty precip or restrictions
Friday. Sub-VFR conditions are then likely at all TAF sites
this weekend due to an enhanced winter storm threat across the
region. Confidence is low within the 5 day lead-time period,
but significant impacts are possible.

&&

.MARINE...
Waves of gusty winds will affect the tidal waters through
midweek. Winds will gust 20-25 kts out of the W/NW through much
of the day, then diminish this evening.

Winds turn southerly with 15-20 kt gusts possible Wednesday
ahead of the next approaching front. This front should come
through dry, with a secondary (dry) front Thursday. A third
front, possibly accompanied by a weak wave of low pressure, will
cross the region Friday. North to northeast flow then increases
heading into the weekend likely prompting SCAs.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 6 PM EST this evening for MDZ008.
     Cold Weather Advisory until 1 PM EST this afternoon for MDZ501-
     510.
     Extreme Cold Warning until 1 PM EST this afternoon for MDZ509.
VA...Cold Weather Advisory until 1 PM EST this afternoon for VAZ504.
     Extreme Cold Warning until 1 PM EST this afternoon for VAZ503.
WV...Cold Weather Advisory until 1 PM EST this afternoon for WVZ503-
     506.
     Extreme Cold Warning until 1 PM EST this afternoon for WVZ501-
     505.
MARINE...Small Craft Advisory until 6 PM EST this evening for
     ANZ530>543.

&&

$$

DISCUSSION...AVS/KLW/DHOF/CJL/KRR
AVIATION...KLW/DHOF/CJL
MARINE...KLW/DHOF/CJL