Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 120815

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
415 AM EDT Mon Mar 12 2018

Low pressure will pass to our south and weaken this morning. Low
pressure will then redevelop off the Carolina coast later today
and then rapidly intensify as it moves northeastward toward the
Canadian Maritimes through Tuesday night. Canadian high pressure
will build southward into the central U.S. and eventually the
southeastern U.S. by Thursday. A weak cold front will push
through the region Thursday night with Canadian high pressure
building overhead for the first half of the weekend.


Regional radars show precipitation overspreading West Virginia,
eastern Kentucky, and western Virginia early this morning
associated with surface low pressure and mid level shortwave
digging southeastward in to the mid south. This low will
continue moving eastward this morning, passing south of our
CWA, as it does it will weaken as a secondary area of low
pressure forms off the Carolina coast later this morning.
Precipitation is expected to finally reach our southwestern
zones in VA/WV over the next few hours, bringing snow to these

Model guidance last evening and overnight has backed off quite a
bit in terms of QPF and extent of precipitation coverage across
our CWA. As a result, we have issued Winter Weather Advisories
for portions of the central Shenandoah Valley, canceling the
Winter Storm Warning. Generally, we are expected 1 to 3 inches
of snow accumulation in the valleys with the potential for 2 to
5 inches along the ridges above 2000 feet. Snow covered roads
are expected in these areas as snow increases this morning,
bringing slippery and difficult travel conditions. Use caution
if travelling through this region this morning.

Elsewhere, snow amounts are expected to be much less, especially
as you near the metro areas, where little to no accumulation
appears most likely at this time. Best chance for accumulating
snow fall will remain across central and southern Virginia.
Check out our winter weather page at for
the latest on forecast snow amounts.

The coastal low pressure will take form later this morning and
early afternoon off the Carolina coast, keeping the axis of
heaviest precipitation south of our region. As this low pressure
rapidly strengthens off the coast and moves northeastward,
models do depict the chances for some snow developing on the
backside of the system, mainly along and east of the I-95
corridor this evening, favoring northern and northeast MD. Not
expecting much in the way of accumulation with this activity,
potentially up to a half inch and residing mostly on grassy and
elevated surfaces.

As low pressure moves quickly northeastward toward New England
overnight, winds will pick up out of the northwest and become
gusty. Upslope snow showers will be ongoing along and west of
the Allegheny Front, where minor accumulations will be possible.
Temperatures will be seasonably cold tonight, falling to the 20s
for most, with at or just below freezing in the cities.


Mid to upper level troughing will remain over the northeastern
U.S. through Wednesday night. We will see the tight pressure
gradient continue across our area, bringing breezy conditions
and colder than normal temperatures. Wind chills during the day
will be in the 20s/30s and teens/20s at night, while single
digits values are likely along our western ridgetops. Shortwave
energy will move along the base of the aforementioned trough,
promoting upslope snows over the favored locations and
potentially snow showers east of the mountains.


Reinforcing front comes through Thu for one last shot of cooler
air. That high pressure area behind the front will settle over
us Saturday morning and then slide offshore allowing for a
moderation in temps.


Increasing moisture and cloud coverage expected this morning as
low pressure passes to the south of the terminals. Latest
guidance indicates the best chance for MVFR/IFR VIS/CIGs will
be at CHO where the best chance for snow resides. Confidence is
much less for terminals further north to experience sub-VFR
conditions as the bulk of the moisture will remain to the south
and east of IAD/DCA/BWI. As low pressure redevelops and
strengthens off the Mid-Atlantic coast this evening, potential
exists for snow to fall near BWI/MTN, resulting in sub VFR
conditions. Confidence of this occurrence is too low to include
in the forecast at this time.

Conditions return to VFR at all terminals by Tuesday morning.
Gusty northwest winds will prevail at the terminals through mid
week as a strong pressure gradient will remain over the
terminals. Upper level energy will swing overhead Tuesday and
Wednesday, bringing the potential for brief periods of sub VFR
conditions in passing snow showers, with the highest chances at


Winds have been on the increase early this morning as low
pressure is approaching from the southwest. A Small Craft
Advisory remains in effect for the lower Bay and Tidal Potomac
early this morning, with all waters in the advisory today and
through the day on Tuesday. Low pressure will develop and strengthen
off the Carolina coast later today and moving northeastward
through tonight. A strong pressure gradient will reside over the
waters through Wednesday as low pressure churns near New England
and Canadian high pressure slides southward in to the central
and southeastern U.S. This will deliver gusty northwest winds
during this time, with the potential for a short period of gale
force gusts Tuesday afternoon/evening.

Wind gusts will be near or above the small craft advisory
criteria Wednesday into Thursday. Therefore, expecting
advisories for most of this period. Winds should decrease into
Friday below criteria but still breezy.


VA...Winter Weather Advisory until 2 PM EDT this afternoon for
     Winter Weather Advisory until noon EDT today for VAZ026-027-
WV...Winter Weather Advisory until noon EDT today for WVZ055-501-
MARINE...Small Craft Advisory until 6 PM EDT Tuesday for ANZ530>533-535-
     Small Craft Advisory until 6 PM EDT Tuesday for ANZ534-537-543.


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