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448
FXUS61 KLWX 161941
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
241 PM EST Thu Jan 16 2025

.SYNOPSIS...
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A clipper system will pass through the area by this evening. High
pressure will build back in for Friday, before multiple waves of
low pressure move through this weekend. There is an increasing
chance for snow on Sunday. An Arctic airmass will build into the
area next Monday through Wednesday with dangerous wind chill
values possible.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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A strong upper shortwave will move overhead through this
evening. As it does so, snow showers will re-invigorate along
and west of the Allegheny Front, with scattered to numerous
flurries and snow showers anticipated to the east of the
mountains (and in particular northern VA, and northern to
central MD including the DC/Baltimore metros around the PM
commute). RAP/HRRR runs remain consistent run-to-run and line
up pretty well with radar/obs in terms of a cluster of snow
showers near MGW that recently dropped visibility to 1/4SM as of
19Z/2PM EST. This cluster will likely cross the area north of
roughly US-50 from WNW to ESE.

Precipitation will taper off east of the mountains tonight as
the shortwave departs. Along and west of the Allegheny Front,
upslope slow will cause a persistence of intermittent snow
showers with patchy light freezing rain or drizzle possible as
moisture depth becomes shallower.
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&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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High pressure will build across the Mid-Atlantic on Friday. This
will result in near normal temperatures and a mainly sunny sky.

A large trough digging across the central CONUS - marking the
leading edge of an Arctic outbreak - will approach the area
Friday night. Some shower activity is possible ahead of this
system Saturday, but overall amounts look to be light. A light
wintry mix is possible over the higher terrain in particular
Saturday morning.

A relative lull is expected Saturday late afternoon and evening
as the initial Arctic front pushes to the east and a wave of
surface low pressure goes with it. A second wave of low pressure
will take shape over the TN Valley, and depending on its exact
evolution could bring precip (snow) to the highlands by daybreak
Sunday morning.
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&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
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Precipitation chances have increased on Sunday with guidance
trending towards a snowier solution. At least a light
accumulating snowfall is becoming more likely across most of the
forecast area. There still remains a bit of uncertainty with
accumulation amounts as the system evolves this weekend. Most
precipitation should wind down Sunday evening, with dry
conditions expected for areas east of the mountains.

Beyond Sunday, the main story will be the cold. At the surface, a
1050+ hPa high will form to the east of the Canadian Rockies, then
track southward along the eastern slopes of the Rockies, eventually
reaching the Gulf Coast/Lower Mississippi Valley as a 1040+ hPa high
by Tuesday night into Wednesday. An area of low pressure will
simultaneously deepen and stall out to the east of Hudson Bay during
that time. Such a configuration will enable a pure Arctic airmass to
be drawn directly southward out of Northern Canada into the eastern
two-thirds of the United States. Strong cold advection will ensue
locally behind Sunday`s system, with temperatures crashing Sunday
night into Monday, and remaining brutally cold through Tuesday and
Wednesday. All signs point to this being the coldest three day
stretch of weather in 5 years. Using Dulles as a proxy for the area,
similar average temperatures to what are being forecast with the
upcoming event last occurred 1/30-2/1 2019, and 1/5-7/2018.

Daytime temperatures are forecast to hold in the teens and lower 20s
for most on Monday, with single digits above/below zero in the
mountains. Winds will gust to around 20-35 mph through much of the
day, making wind chills -15 to -35 in the mountains, and -5 to 15 at
lower elevations. Air temperatures will drop back to below zero
roughly west of I-81 Monday night, with single digits above zero
further east. Wind chills should reach below zero in nearly all
locations Monday night, with central Virginia potentially being the
lone exception. Slightly lower daytime temperatures and slightly
lesser winds will result in similar wind chills during the daylight
hours again on Tuesday (-15 to -35 in the mountains, -5 to 15 at
lower elevations). Temperatures will once again drop into the single
digits above/below zero Tuesday night. Some very slight warming is
expected by Wednesday, with temperatures forecast to reach into the
teens and lower to middle 20s. Winds will also be a bit lighter,
enabling wind chills to make it into the single digits above/below
zero at higher elevations, and teens at lower elevations. Cold
Weather headlines will likely be needed at times Sunday night
through Tuesday night.

Conditions will remain dry on Monday through Tuesday morning. By
Tuesday afternoon into Tuesday night there are some hints that a
system may develop along the Gulf Coast and track to our south. Most
guidance favors this system staying far enough south that all
precipitation will also stay to our south. However, there are some
ensemble members that track the system a bit farther north, leading
to snow spreading northward into our area. We will continue to
monitor this system over the upcoming days.
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&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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SCT/BKN clouds around 4 kft will persist into this evening,
though intermittent/brief drops to low-end MVFR are possible as
snow showers cross (north of CHO). VSBY may also briefly drop,
perhaps as low as IFR/LIFR briefly in the heaviest snow showers
21Z-02Z from west to east (again, north of CHO). S winds could
gust to 15 kts at times into this evening before shifting to the
west as skies clear and the system driving the snow showers
exits to the east.

VFR is expected through Friday night, though sub-VFR returns
Saturday as another frontal system moves in. Winds S Friday
become NW by Saturday night. Overall, precip amounts look light
and in the form of rain Saturday, though there could be a brief
wintry mix at onset Saturday morning.

Sub-VFR conditions are becoming increasingly likely Sunday with the
potential for some accumulating snow throughout the day,
possibly into the evening. Winds out of the northwest will be
gusting 15 to 20 knots. VFR conditions build in on Monday with
winds remaining out of the northwest but gusting more in the 20
to 30 knot range at times.
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&&

.MARINE...
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Southerly winds will become lighter and shift westerly this
evening, then increase out of the west/northwest overnight into
Friday morning as high pressure builds in. The high will move
offshore and could result in some channeling Friday night. Winds
then shift to the northwest and increase by Saturday night as an
Arctic front moves through.

SCAs are expected Sunday as the potential for snow moves over
the waters. By Monday, drier conditions arrive but gusty
northwest winds nearing 30 knots will come along with it. Gale
force winds are possible during the day on Monday. Freezing
spray conditions will be possible Sunday night into Monday.
-- End Changed Discussion --

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Winter Storm Warning until 7 AM EST Friday for MDZ001.
VA...Winter Weather Advisory until 1 AM EST Friday for VAZ503.
WV...Winter Storm Warning until 7 AM EST Friday for WVZ501-505.
MARINE...Small Craft Advisory until 6 PM EST this evening for
     ANZ530>543.
     Small Craft Advisory from 11 PM this evening to noon EST
     Friday for ANZ531>534-537-539>541-543.

&&

$$

SYNOPSIS...LFR/DHOF
NEAR TERM...DHOF
SHORT TERM...DHOF
LONG TERM...ADM/KJP
AVIATION...DHOF/ADM
MARINE...DHOF/ADM