Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 191444

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1044 AM EDT Mon Mar 19 2018

High pressure off the Mid Atlantic coast will push out into the
western Atlantic this afternoon as low pressure moves across the
Tennessee Valley. Coastal low pressure will emerge and strengthen
off the Mid Atlantic coast on Tuesday. Another low pressure system
will develop off the Carolina coast Tuesday night, passing south
of our region. Canadian high pressure returns for the latter half
of the work week.


Temperatures as of 10am are in the lower to middle 40s. Cloud
cover aligns the Blue Ridge Mountains and areas to the east and
south. Winds are light and variable across the region. Quiet
weather now, but two developing winter storm systems are
expected to impact our region beginning this evening through
much of the day Wednesday.

Expect increasing clouds the remainder of the day from
southwest to northeast with the approaching first winter storm
and its associated warm front. Although temperatures quickly
rose through the 30s and into the middle 40s in most places, the
quick ascent of these temperatures will be slowed due to the
cloud cover. Highs this afternoon will reach the lower 50s for
most while remaining in the 40s in the mountains.

Low pressure will track across the Tennessee Valley this
afternoon and approach our area this evening. Expect much of
the precipitation to hold off until after midnight for most,
with light rain likely across Central VA this evening.
Precipitation types should be mainly rain as temperatures
remain in the upper 30s to lower 40s. There is a concern for a
mix of rain, snow, sleet and freezing rain along our far
western zones in WV and western MD overnight. No advisories
issued at this time as snow and sleet accumulations look to
remain just below criteria. There is a possibility that if thermal
profiles continue to show a freezing rain potential, then
advisories may be needed later this afternoon and tonight.


The transition from rain to a wintry mix across the area will
continue southward throughout the day on Tuesday as the low moves
off to our northeast, filtering in additional cold air. There will
be a lull in precipitation Tuesday afternoon and early evening as
the low pulls away from the area and another low pressure area
emerges off the Carolina coast overnight Tuesday.  As this low moves
northeastward Tuesday night and early Wednesday, low pressure will
reside at the surface and aloft over WV, helping spread snowfall
across much of the area. Confidence is increasing for at least
advisory criteria for portions of the area overnight Tuesday and
early Wednesday, but confidence in warning criteria is not there at
this point. See our winter weather page at
for the latest snowfall accumulations.

Some of the biggest uncertainties at this time through Tuesday
evening is whether or not any of the wintry mix or snow will
meet criteria in order to issue a watch or advisory, especially
east of the Blue Ridge Mountains. The NAM tends to keep all rain
through Tuesday morning with a tendency of freezing rain being
introduced around rush hour and lingering through mid afternoon.
This followed by sleet and snow later Tuesday afternoon through
Tuesday night. The GFS begins as a rain and snow mix Tuesday
morning, transitioning over to snow and sleet the remainder of
the day into Tuesday evening. This would be followed by all snow
Tuesday night into early Wednesday. The European model lies
between both solutions through Tuesday evening with a lean
toward the GFS model.

The recent model guidance Low pressure will pull away from the
area during the day on Wednesday, bringing an end to
precipitation by the evening. Temperatures through the period
will remain below normal as cold air advection wins out along
with precipitation and ample cloud cover affecting the region.


High pressure will be building in from the west on Thursday. There
will still be a little moisture in the northwest flow aloft, so some
cloud cover could linger. It will also be breezy with high
temperatures 10-15 degrees below normal (40s for most areas).
The high will cross the area Friday and Friday night, and
temperatures will remain below normal.

The next low pressure system will be ejecting out of the Plains
toward the Mid Atlantic over the weekend. Although the system is
resolved in most guidance, there is still a wide spread for track
and timing, and thus thermal profiles. Will employ a generic
rain/snow forecast at this juncture based on blended model


VFR conditions will persist through this afternoon at all
terminals. MVFR/IFR VIS and CIGs expected to overtake the
terminals tonight as low pressure approaches from the south,
bringing precipitation from south to north starting this evening
and continue into the day on Tuesday. A break in precipitation
Tuesday afternoon could provide some improving conditions, but
likely remain MVFR. Another low pressure area poised to bring
wintry precipitation to the terminals Tuesday night and early
Wednesday, resulting in continued MVFR/IFR VIS and CIGs. Winds
are expected to be east southeast this afternoon, backing out
of the north to northeast tonight, remaining at 10 knots or

VFR conditions are expected Thursday into Friday as high pressure
builds into the area. Northwest winds may gust greater than 25 kt on


High pressure residing east of our waters this afternoon will
promote winds remaining below advisory criteria. Low pressure
will move south of our area tonight and redevelop off the coast
early Tuesday. This will bring SCA conditions across our waters
starting tonight. A Gale Warning has been issued for the lower
Chesapeake as the low strengthens and passes to our east,
delivering a strong pressure gradient over the waters. Small
Craft Advisories continue through the day on Tuesday and will
likely be required through the day on Wednesday as another low
pressure area approaches the waters from the south.

The region will be in between departing low pressure and high
pressure to the west for Thursday and Friday. Small Craft Advisory
conditions in northwest flow will be most likely on Thursday, and
could linger into Friday on portions of the waters.


Two areas of low pressure will pass off the coast Tuesday and
Wednesday, resulting in prolonged onshore flow. Water levels
will be rising during this time, with minor flooding becoming
possible by Wednesday. Exact projections are still uncertain at
this time though.


MARINE...Small Craft Advisory from midnight tonight to 4 PM EDT Tuesday
     for ANZ531>533-537-539>542.
 Small Craft Advisory 6 AM EDT through 4 PM EDT Tuesday for
ANZ530- 535-536-538. Small Craft Advisory from midnight tonight
to 6 AM EDT Tuesday for ANZ543. Gale Warning from 6 AM to 4 PM
EDT Tuesday for ANZ534-543. Small Craft Advisory from 6 PM this
evening to 6 AM EDT Tuesday for ANZ534.


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