Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 150853
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
353 AM EST Fri Dec 15 2017

.SYNOPSIS...
Low pressure will develop along the North Carolina coast this
morning, moving northeastward and out to sea tonight. High
pressure will return for Saturday before weak low pressure
impacts the area early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
An area of low pressure off the Carolina coast will move
northeastward today, bringing light snow to the metro areas by
this afternoon. As a result, a Winter Weather Advisory is in
effect from 1pm this afternoon through 7pm this evening for
Metro Baltimore and the District of Columbia, including the
northern and eastern suburbs. Snowfall totals will be on the
order of one to perhaps two inches across the advisory area,
with the higher amounts expected to reside near the Baltimore
area, and extending to the northeast.

A sharp gradient will exists to the west of the metro areas,
and exactly where this gradient falls will determine where the
accumulating snow will cease. Temperatures throughout the day
will hold at or slightly above the freezing mark, and with
favorable atmospheric profiles, any precipitation that falls
will be in the form of snow. Couple this with road temperatures
expected to remain at or below freezing during the event,
conditions could turn icy on untreated road surfaces. The snow
will exit the area to the northeast by early Friday evening.
Upslope snow showers are expected across the Allegheny Front
Friday evening as northwest flow takes hold. Accumulations up to
one inch will be possible in those favored locations.
Temperatures overnight will drop down in to the middle to upper
20s as skies start to clear.


&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
High pressure builds in across the area on Saturday and Saturday
night with dry conditions expected. Temperatures will top out
during the day on Saturday in the upper 30s to middle 40s, with
overnight lows in the 20s to near freezing in the metro area.

High pressure will reside to our south on Sunday, resulting in
southerly flow across the region. This will generate moderating
temperatures in the mid to upper 40s. Conditions will remain dry
during the day with high clouds beginning to stream overhead
ahead of an approaching shortwave trough that will cross the
region Sunday night and early Monday morning. There is a slight
increase in precipitation as a result, but moisture looks
limited and with marginal temperatures, most favored
precipitation will be light rain showers across our northern
zones. Lows overnight Sunday will bottom out in the mid to upper
30s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
East coast 500 mb ridging will be the dominant feature for the
extended forecast. Consequently, as shortwave energy traverses the
CONUS Tuesday, the primary precip type will be rain. And, since the
northern and southern streams will remain unphased, it`s looking
like a lighter QPF amount for the DC/Baltimore metro. Will be
carrying slight chance PoPs for most, chance for the mountains.

High pressure and mild conditions will prevail for the balance of
the week.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
Predominate VFR conditions are expected through Sunday. A period
of light snow is expected across our eastern terminals this
afternoon and early Friday evening, which could result in
periods of reductions to DCA/BWI/MTN. High pressure builds in
to the area Saturday and Sunday with light to moderate westerly
winds of 10 knots or less.

VFR will likely prevail Mon-Tue. There will be an impulse moving
through, so precip and flight restrictions will be possible, but
confidence low.

&&

.MARINE...
Low pressure passing to our east today and a cold front crossing
the region will bring gusty winds Friday night into Saturday. As
a result, SCA will go in to effect Friday night and will likely
be extended into Saturday. Winds expected to remain below
advisory criteria on Sunday.

No hazards anticipated Monday into Tuesday. Winds will increase
thereafter, but any flags may hold off til beyond current forecast
period.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Winter Weather Advisory from 1 PM this afternoon to 7 PM EST
     this evening for DCZ001.
MD...Winter Weather Advisory from 1 PM this afternoon to 7 PM EST
     this evening for MDZ004>006-011-013-014-503>508.
VA...Winter Weather Advisory from 1 PM this afternoon to 7 PM EST
     this evening for VAZ054.
WV...None.
MARINE...Small Craft Advisory from 9 PM this evening to 6 AM EST
     Saturday for ANZ530>533-538>541.
     Small Craft Advisory from 3 PM this afternoon to 6 AM EST
     Saturday for ANZ534-537-543.

&&

$$
SYNOPSIS...BKF
NEAR TERM...BKF
SHORT TERM...BKF
LONG TERM...HTS
AVIATION...BKF/HTS
MARINE...BKF/HTS


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