FXUS61 KLWX 160853

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
353 AM EST Sat Feb 16 2019

Low pressure will track east across North Carolina today. An
area of high pressure across the Great Lakes and the northeast
will briefly build into the Mid Atlantic tonight. Low pressure
will follow, crossing the area Sunday afternoon and evening.
High pressure will build to our north early next week. Stronger
low pressure may impact the area during the middle portion of
next week.


Last night's cold front remains along the eastern seaboard from
Cape Hatteras up through New England. Temperatures remain in the
40s, to lower 50s in central Virginia and southern Maryland.
(Today's calendar day highs will likely be the midnight readings.)
Even at the higher elevations, temperatures still in the mid-
upper 30s. There are a few radar echoes along this boundary, but
the only reports are sprinkles.

Low pressure across southeastern Tennessee will cross southern
North Carolina this morning. There will be enough positive
vorticity advection and jet dynamics for a period of
precipitation to spread north into central Virginia and southern
Maryland this morning. However, temperatures are only marginally
cold enough for snow. Latest guidance suggests highs will be in
the mid-upper 40s; have raised the forecast highs be a degree or
two. Consequently, have reduced the snowfall forecast, and
cancelled the Winter Weather Advisory for the central Blue
Ridge. Still believe there will be accumulating snow across the
ridge, but forecast totals approximately cut in half; ie: less
than an inch.

For the rest of the area, the day will start out mostly cloudy,
but as drier air advects southeast believe skies will clear. In
the lowlands, temperatures will be too warm for snow. Any rain
will be light. Temperatures will be close to climo.


High pressure building from the Great Lakes to northern New
England tonight will build into the Mid Atlantic, providing a
mostly clear and mostly calm night. Temperatures will drop below
freezing areawide. There is a potential for stronger radiational
cooling, but overnight warm advection and dewpoints in the mid
20s may impede a greater freefall.

The next shortwave and surface reflection will approach Sunday
afternoon. In this case, the surface low will be tracking across
the forecast area, with positive vorticity advection and jet
dynamics moving into Pennsylvania. This storm track will allow
warm(er) air to spread into Virginia in the 850-700 mb layer,
making it less likely to receive accumulating snow. However,
there will be some low- level cooling (centered near 900-950
mb), assisted by nocturnal cooling as precip extends into the
evening. That makes precip type forecasting more challenging. At
this point, am keeping highs in the 30s. However, subfreezing
temperatures will be limited, so am not as concerned about
freezing rain. (Northern Maryland likely will be an exception
to that statement.) Consequently, rain and sleet are the two
weather types left, and they will dominate the afternoon and
evening forecast. Freezing/frozen accumulations will be minimal
at best, but wouldn't rule out a trace of either after dark.

High pressure will be building on Monday, but a few lingering
showers will be possible, especially in the morning. By
afternoon temperatures should rebound well into the 40s.


Canadian high pressure residing over the Upper Midwest will migrate
eastward during the day on Tuesday, building to our north through
Tuesday evening. This will deliver dry conditions and slightly below
normal temperatures under a light northerly flow. At the same time,
an upper trough will be lifting out of the southwestern states,
aiding in the development of an area of low pressure near the lower
Mississippi Valley. This low will strengthen and gather ample
moisture from the Gulf as it tracks northeastward into Tuesday
night. Clouds will be on the increase Tuesday afternoon and evening,
but dry conditions are expected to prevail through midnight. After
which, precipitation will spread northward into the region, and with
the high situated to our north, cold air will be funneled and locked
in across our area. A rain/snow mix will be possible across the
southern half of the CWA predawn Wednesday, with snow the favored
across the north given colder temperatures at the surface and aloft.

As the system progresses northward during the day on Wednesday, warm
air advection will be increasing aloft, as 850 temps likely rising
above freezing by Wednesday evening for much of the area. This will
bring a transition to a wintry mix throughout the day across the
area as low level cold air hangs on for portions of the area. It is
still too early to discern exact ptype and timing, but one thing is
becoming more and more clear is the plentiful moisture associated
with this system. QPF will likely approach or exceed an inch for a
bulk of the area through Wednesday night. Depending on the strength
and stubbornness of the cold air at the surface, those
climatologically favored locations near and west of the Blue Ridge
could see an extended period of wintry precipitation Wednesday and
Wednesday night.

By Thursday morning, low pressure off the Mid Atlantic coast will be
pushing northeastward into the Atlantic as high pressure nudges into
the region from the west. This should bring an end to precipitation
by Thursday afternoon, and with continued warming temperatures at
the surface and aloft, rain will be favored across the CWA Thursday
morning. High pressure to the north will deliver mostly dry
conditions into Thursday night, before another area of low pressure
approaches from the Tennessee Valley late Friday and Friday night.
Wintry precipitation will be possible for portions of the area
Friday night.


VFR flight conditions will prevail today, even at CHO which will
be nearer to a passing disturbance. Northwest winds 10-20 kt
will be diminishing through the day. Most ceilings will be mid
deck, except at CHO.

Another disturbance will cross the terminals Sunday afternoon-
evening. Higher confidence that the area will receive
precipitation, however temperatures will remain a pinch too warm
for snow. Think rain/sleet will dominate, but would not
completely rule out freezing rain or snow, especially at MRB. At
this point, am not confident in any accumulations.

VFR conditions Monday through Tuesday evening as high pressure
builds to the north of the terminals promoting a light northerly
flow and dry conditions. A large area of low pressure will
cross the terminals late Tuesday night through Wednesday night,
with mixed precipitation expected. This will likely bring an
extended period of sub VFR conditions.


Northwest gusts hovering around 20 kt early this morning Small
Craft Advisories remain in effect. Will slowly peel back upper
waters after daybreak, and all waters by 10 am. At this point,
that timing seems reasonable.

A disturbance will pass south of the waters this morning, with
another disturbance crossing the area Sunday afternoon/evening.
Each of these systems appear weak, and will not produce a
pressure gradient. As a result, Winds will remain rather light
through the rest of the weekend.

High pressure builds Monday. Will need to assess if there will
be enough of a gradient for a potential Small Craft in this
window. It appears likely at this time.

High pressure will reside north of the terminals on Tuesday under a
light northerly flow. Low pressure will cross the waters Wednesday
and Wednesday night, with the gradient expected to remain weak
enough for sub SCA conditions to win out.


MARINE...Small Craft Advisory until 6 AM EST early this morning for
Small Craft Advisory until 10 AM EST this morning for


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