617
FXUS61 KLWX 150245
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
945 PM EST Tue Jan 14 2025

.SYNOPSIS...
A reinforcing cold front will move through the area tonight.
High pressure will briefly build toward the area Wednesday,
before a clipper system approaches from the northwest on
Thursday. High pressure is expected to build back in for Friday,
with a stronger low pressure system expected over the weekend.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Snow showers and squalls will continue to move out of southwest
PA into western MD, particularly Garrett County, MD for another
2 to 3 hours. Snow has accumulated a couple of inches since late
this afternoon. Additional 1 to 3 inches will be likely in
western and central parts of Garrett County during this
timeframe.

Another area of snow showers is noted along the Loudoun and
northern Fauquier County line and sliding to the southeast.
These snow showers could leave a light coating of snow on roads
making for slower or slippery travel. This area of snow showers
will make its way to the I-66 corridor and US 15, 17, and 29, so
take caution while driving.

There will be a strong surge of winds overnight in the wake of
the cold front. This will hold temperatures up (mid teens to
lower 20s) but bring down wind chills. Widespread wind chills in
the single digits are expected late tonight but should remain
above Cold Weather Advisory criteria for much of the area,
However, wind chills will reach -10 to -20 in the Alleghenies
and along the Blue Ridge, where Cold Weather Advisories have
already been issued.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Previous discussion...
High pressure will build to the southwest Wednesday, leading to
decreased snow shower activity in the mountains, and completely
dry conditions further east. However, the pressure gradient will
remain tight, with blustery WNW winds gusting 20-35 mph. The
cold advection will result in highs only in the mid 20s to mid
30s. Wind chills will remain the in the mid teens to mid 20s,
with near to below zero in the higher elevations.

A clipper system embedded in northwesterly flow aloft will
track toward the area on Thursday. This system will have
slightly more moisture to work with, and should produce a
period of snow showers in the mountains Thursday into Thursday
night. Snow may be moderate to heavy at times with relatively
high snow ratios. Current projections are for 3-6 inches of snow
in the Alleghenies, but amounts have been trending higher. Flurries
will once again be possible to the east of the mountains, and
there is a small chance for some steadier snow showers to spread
east and produce a quick coating of snow. Locations between the
Alleghenies and Blue Ridge (I-81 corridor), as well as northern
Maryland should have the best chance (east of the Alleghenies)
to experience steadier snow during this time. It will be yet
another cold day, with mostly cloudy skies and high temperatures
in the upper 20s to mid 30s at lower elevations and 20s in the
mountains.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Synoptically, broad upper level troughing will continue to reside
over the eastern half of the CONUS with ridging across the western
U.S. Ensemble and deterministic guidance continues to remain
persistent on upper level troughing holding firm over the eastern
U.S and central U.S through the middle of next week. Embedded in the
trough will be a series of shortwave disturbances and an Arctic
front that looks to cross the area this weekend into the start of
next week. The features of most concern look to push across the area
Saturday into Saturday evening and late Sunday into early Monday.
These two time periods look to be the best windows of opportunity
for increased precipitation chances across the region.

Brief high pressure builds back into the area Friday before sliding
off the VA/NC coast Friday evening into Friday night. As a result,
expect south to southwesterly flow to ensue Friday afternoon
boosting temperatures back into the 40s for daytime highs east of
the mountains. Dry conditions will continue into Friday night with
increasing clouds late as high pressure pushes further offshore.
Lows Friday night will fall back into the upper 20s and low 30s.

By Saturday, we await the arrival of low pressure tracking out of
the southern Plains/lower MS River Valley toward the Carolinas.
Increasing isentropic lift and warm air advection ahead of this
system will allow precipitation to break out across areas west of
the Blue Ridge early Saturday morning into Saturday midday.
Precipitation will then work east of the Blue Ridge and toward the
metros late Saturday morning and evening before diminishing east of
the mountains Saturday night. Models remain a bit disjointed with
the main energy source Saturday although confidence continues to
increase for some wintry precipitation especially at the onset along
and west of the Blue Ridge and perhaps along the PA/MD line as
antecedent cold temperatures will remain in place. Elsewhere, rain
is expected as southerly flow increases in the mid-levels Saturday
morning into Saturday afternoon. Mountain locations especially west
of the Alleghenies could hold onto mixed precipitation through the
entirety of the event. High temperatures Saturday will push into the
mid to upper 40s with 30s across the high valleys of the Blue Ridge
and Allegheny Front. Lows Saturday night will fall back into the mid
to upper 20s and low 30s.

The cold front will work south and east of the area Sunday into
Sunday night. Cold air advection will quickly race in along with
lingering mountain upslope snow showers. Meanwhile, the front will
reside toward the coast with a trailing low pressure system racing
north and east from the Carolinas and toward the New England coast
late Sunday into Monday morning. Some uncertainty remains in regards
to this storm system especially when it comes to intensity (i.e
forcing) and moisture advection during the aforementioned timeframe
above. For now, went with a blend of ensemble and deterministic
guidance leaving a chance of snow in the forecast Sunday into Sunday
into Sunday night. Precipitation chances look to gradually decrease
Monday into Tuesday as 1045-1050 mb Arctic high pressure builds into
the region. High temperatures Sunday will top out in the mid to
upper 30s and low 40s with 20s in the mountains. By Monday and
Tuesday, high temperatures will struggle to get out of the 20s with
850 mb temperatures in the -16 to -21 degree C range. Low
temperatures Monday and Tuesday nights will fall into the teens and
single digits with wind chills following a similar trend.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions are expected through Wednesday night, though a
period of sub-VFR ceilings are expected this evening near IAD.
Winds will be out of the WNW through Wednesday night. An
increase in winds late this evening with a surge of 25-35 knots
overnight as a cold front moves through. There may be a
relative decrease around sunrise before 25-30 knot gusts resume
through the day on Wednesday.

Winds will lessen Wednesday night then become southwesterly on
Thursday. A clipper system will affect the region Thursday into
Thursday night. There is a low chance of MVFR conditions and a
brief period of light snow or flurries, mainly at MRB.

VFR conditions are expected Friday into Friday night with high
pressure nearby. Westerly winds will switch to the south and
southwest Friday afternoon and night as high pressure pushes
offshore. Increasing clouds and southerly winds are expected Saturday
ahead of a strong cold frontal boundary. Sub-VFR conditions look to
return Saturday morning into Saturday evening as widespread
precipitation chances are expected across the terminals. Additional
sub-VFR conditions are expected Sunday as another wave of low
pressure pushes through. Winds will remain elevated out of the
northwest in the wake of the departing frontal boundary.

&&

.MARINE...
A surge of stronger winds in northwesterly flow will occur
tonight behind a reinforcing cold front. Gale Warnings are in
effect for all waters tonight. SCAs will likely be needed
Wednesday through at least part of Wednesday night in continued
northwesterly flow. Winds finally decrease to sub-SCA levels out
of the southwest on Thursday, but could near low-end SCA levels
over the widest waters. A clipper system pushing through
Thursday night could also lead to a slight uptick in winds.

Sub-SCA level westerly winds are expected through the front half of
Friday as high pressure sits nearby. Winds will turn to the south
and southwest Friday afternoon and night as high pressure pushes
offshore. SCA conditions will likely return to the wider waters
Friday night and into Saturday due to southerly channeling.
Northwest winds are expected in the wake of the boundary Saturday
night with near SCA level winds expected Sunday in post-frontal
northwest flow.

&&

.TIDES/COASTAL FLOODING...
Offshore flow behind a series of fronts is resulting in
declining water levels. The strongest negative surge will take
place tonight into Wednesday, when blowout conditions will be
possible. Water levels will return closer to normal by Thursday
as winds take a more southwesterly direction.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Gale Warning until 6 AM EST Wednesday for MDZ008.
     Cold Weather Advisory until noon EST Wednesday for MDZ001.
     Cold Weather Advisory until 10 AM EST Wednesday for MDZ501.
VA...Cold Weather Advisory until noon EST Wednesday for VAZ503.
     Cold Weather Advisory until 10 AM EST Wednesday for VAZ504-507-
     508.
WV...Cold Weather Advisory until noon EST Wednesday for WVZ501-505.
     Cold Weather Advisory until 10 AM EST Wednesday for WVZ503-506.
MARINE...Gale Warning until 6 AM EST Wednesday for ANZ530>543.

&&

$$

SYNOPSIS...ADS
NEAR TERM...ADS/KLW
SHORT TERM...ADS
LONG TERM...EST
AVIATION...KLW/EST
MARINE...KLW/EST
TIDES/COASTAL FLOODING...KLW