Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 031549
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1049 AM EST Sat Dec 3 2016

.SYNOPSIS...
High pressure will gradually move into the region through Sunday.
An upper-level disturbance will pass through the area Sunday night
and high pressure will briefly return for Monday. Coastal low
pressure will impact the area Tuesday before high pressure briefly
returns for Wednesday. A potent cold front will move through late
next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
High pressure will slowly progress eastward from the Midwest and
into the mid-atlantic states by tonight. However we are still
feeling the effects of the system departing southeastern Canada
with another day of persistent northwest flow. Snow and freezing
drizzle along the Allegany Front has generally ended, so have
allowed Winter Weather Advisory to expire.

Otherwise, cloud cover will be similar to yesterday with more
clouds north and west, and more sun south and east, as is
typical in northwest flow. Temperatures will be near seasonal
normals with highs from the 40s to low 50s. A breeze is expected
again as well with some gusts 20-25 mph.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
Surface high pressure will move across the region tonight, leading
to slackening winds and dry weather. However, high cirrus clouds
will already be increasing aloft ahead of the next system coming
out of the plains. Lows will be in the 20s/30s.

Northern stream energy will eject out of the plains on Sunday with
southwest flow/warm air advection developing ahead of it. This
will continue to lead to thickening and gradually lowering clouds
on Sunday. The weakening system will then traverse the area late
Sunday and Sunday night. Most of the southern stream
energy/moisture located over the deep south will remain untapped,
so while a period of light precipitation is likely, amounts will
be on the low side. Thermal profiles favor predominantly rain for
the metros and the I- 95 corridor south and east. However some
light snow is likely for areas to the north and west and a light
accumulation is possible in the higher elevations. Highs Sunday
will be in the 40s area-wide, with lows in the 30s Sunday night.

High pressure and dry weather will then move in behind the system
for Monday with highs in the 40s to low 50s.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Low pressure will track through the Gulf Coast States into the
Tennessee Valley Monday night. The surface ridge from high
pressure over New England will continue to extend southwest into
our area. Clouds will lower and thicken as the low approaches from
the southwest...and precipitation may begin to overspread the area
overnight from southwest to northeast.

The low will slowly move northeast into the Ohio Valley Tuesday
while it transfers its energy to a coastal low along the North
Carolina Coast. Warm and moist air from the Gulf of Mexico and
Atlantic Ocean will overrun the surface cooler air in
place...likely resulting in a soaking rain for most areas.
However...there still remains some concern with precipitation
type. There will be plenty of dry air ahead of the system and as
precipitation into the dry air...it may lead to insitu cold air
damming from evaporative cooling. The cooling effect may be enough
for snow or, perhaps more likely, sleet to fall late Monday night
through Tuesday...especially for the the ridge tops. This will
have to be monitored since uncertainty remains high this far out.
Any snow or sleet should change over to rain Tuesday afternoon as
warmer air takes over with the primary low moving off to our
north.

Coastal low pressure may hang around for Tuesday night before
finally moving off to the east on Wednesday. Have increased pops
for Tuesday night with rain likely across most areas. Any leftover
rain should end Wednesday morning and high pressure will briefly
bring drier conditions for Wednesday afternoon.

A strong cold front will pass through the area late in the week.
Blustery and much colder conditions are expected by Friday.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
Predominantly VFR conditions expected through at least Sunday.
Scattered-broken stratocumulus deck at 4000-6000 feet will
continue with varying coverage through today. This will be
replaced by an increasing high cirrus deck tonight and on Sunday.
Clouds will lower and thicken Sunday night as a weakening system
moves through, along with the chance for some light rain, and
possibly some light snow at MRB. Thus a period of sub-VFR
conditions are possible. Monday will see an improvement back to
VFR at all TAF sites.

Winds will be out of the west/northwest through today, with gusts
up to 20-25 knots. Winds will decrease tonight and turn light
southerly Sunday afternoon and Sunday night, before turning back
to the north Monday.

VFR conditions will persist for most of Monday night. Rain and
subvfr conditions are expected either late Monday night or Tuesday
morning. IFR conditions are possible later Tuesday through
Tuesday night along with more rain. Conditions will improve
Wednesday.

&&

.MARINE...
Small Craft Advisory remains in effect for all waters through
today for persistent gusty northwest flow with gusts in excess
of 20 knots. Winds begin to decrease tonight, but SCA will
continue through tonight for portions of the central Chesapeake
and lower Tidal Potomac. Winds finally drop below SCA criteria
Sunday and remain below through Monday.

Coastal low pressure will develop Tuesday before slowly moving out
to sea later Tuesday night into Wednesday. A Small Craft Advisory
may be needed for portions of the waters Tuesday into Wednesday.
High pressure will briefly build overhead later Wednesday before a
potent cold front approaches Thursday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until midnight EST tonight for ANZ531-532-
     538>540.
     Small Craft Advisory until 6 PM EST this evening for ANZ530-
     535-536-542.
     Small Craft Advisory until 6 AM EST Sunday for ANZ533-534-537-
     541-543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...MM/RCM
SHORT TERM...MM/RCM
LONG TERM...BJL/RCM
AVIATION...BJL/MM/RCM
MARINE...BJL/MM/RCM



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