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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
321 PM EST Thursday Feb 11 2016

Synopsis...
high pressure builds in across the region through Friday. A
strong cold front will cross the region Friday night with Arctic
high pressure building in the wake for the weekend. Low pressure
may impact the area Monday and Tuesday.

&&

Near term /until 6 am Friday morning/...
surface high pressure poised over the upper MS valley this afternoon.
Middle-Atlantic still remains under cyclonic flow with long-wave trough
over eastern North America. However heights gradually rising and bl
moisture thinning as evident in recent visible satellite. Threat for
flurries and isolated snow showers across northern Maryland will continue to
wane. The gusty winds will also diminish during the late afternoon
as the high builds.

The high slips to the south tonight. Any upslope snow showers will
quickly come to an end this evening. Otherwise just a cold night
with lows in the teens in most locations. Wind chills will be less
of a concern with the lighter winds.

&&

Short term /6 am Friday morning through Saturday night/...
surface high pressure quickly slides offshore early Friday with return
flow bringing slightly higher temperatures (but still on either side
of freezing)...as well as increasing clouds/moisture. One low
pressure center associated with an Arctic front will be moving
through the Great Lakes...while another takes shape near the
Carolina coast in response to a southern vorticity maximum. Majority of
guidance keeps the coastal low effects to our southeast...but did
introduce low end probability of precipitation across southern Maryland.

The more important weather feature for our area will be a pair of
boundaries trailing the northern low center. Increasing signal in
model guidance of a band of snow showers developing ahead of the
first boundary and have thus increased probability of precipitation across the area with
sufficient moisture available. Still some differences on timing and
coverage...but there is potential for these snow showers to reach
the metropolitan area during portions of evening rush hour. With the
antecedent cold conditions...any snow would stick on untreated
roads. Certainly a situation to pay attention to.

This will also mark the beginning of a period of upslope
snow...heaviest Friday afternoon and night...but lasting through
Saturday. Winter Weather Advisory possible as several inches of snow
expected.

Second boundary will move through late Friday night and mark the
leading edge of the coldest airmass. Even though chances decrease a
bit...some snow showers could still make it across especially
northern parts of the area. Temperatures will fall into the teens in
most area and winds increase substantially with gusts of 20-30 miles per hour
behind the front. This may necessitate wind chill advisories in the
higher elevations.

Saturday-Saturday night will be the coldest of the stretch with 850
mb temperatures below -20c and stiff winds. Highs on Saturday will only be
in the teens and 20s with lows Saturday night in the single
digits...and below zero in the Potomac Highlands. Wind gusts of at
least 30-40 miles per hour will occur Saturday...and there is a chance of Wind
Advisory criteria. The winds will only diminish slightly Saturday
night. Wind chills may fail to rise above +10f on Saturday in much
of the area...and fall below zero Saturday night. Wind Chill
Advisory criteria (-5f) will likely be met over most of the
area...and wind chill warnings (-25f) are possible along the
alleghenies.

Other issue for Saturday will be a continued chance of snow showers
and streamers across the northern part of the area. Snsq parameter
in the NAM and GFS...and even 12z GFS quantitative precipitation forecast output...place the favored
area across north central Maryland including Baltimore.

&&

Long term /Sunday through Thursday/...
latest model guidance is suggesting a pretty quick erosion of an
impressively cold airmass beginning late Sunday and into early next
week. Normally this type of quick erosion would force some kind of
precipitation...and as such a lot of the guidance is trying to bring
some precipitation over the area Sunday night into Monday.

A strong upper-level disturbance will force a surface low over the
southeastern Continental U.S....which will then move northeast near or over the
area. Guidance diverges greatly on surface low track and how much
cold air is left in place. Best chance for prolonged wintry
precipitation would be west of the Blue Ridge mountains. East of
there precipitation may very well change to rain by Tuesday. There
will likely be some wintry precipitation early next week...but
amounts are highly uncertain at this time.

An active pattern may persist into the middle part of next week but
details are fuzzy given the uncertain evolution of the early week
system.

&&

Aviation /20z Thursday through Tuesday/...
primary issue affecting the terminal through the weekend will be
wind. West-northwest gusts up to 30 knots will quickly diminish this evening and
any lingering ceilings at 050-060 will dissipate. VFR through the bulk
of Friday with light SW winds. Will have to watch for snow showers
ahead of an Arctic cold front late Friday afternoon into evening.
Not high enough confidence to put in the extended tafs now...but
these could cause brief impacts.

Winds increase sharply behind front...with northwest gusts 25-35 knots
continuing through Saturday and only gradually diminishing Saturday
night. There will be a lingering threat of isolated/scattered snow showers
through Saturday...especially BWI/mtn.

Sub-VFR possible Sun night into Monday if precipitation develops. Winds
light Sun night bcmng gnly Ely Monday.

&&

Marine...
west/northwest winds continuing to gust to 30 knots through this afternoon but
quickly dropping off this evening. The Small Craft Advisory over the Bay may be able
to be canceled early as winds are forecast to lighten after
midnight. Light SW flow to start Friday but that will quickly change
during the evening as Arctic front moves through with chance for
snow showers. West/northwest winds will increase immediately and will be
issuing Small Craft Advisory. This may need to be upgraded to a Gale Warning...but
confidence not high in that occurring until after 12z Saturday.
Gales then appear likely Saturday and a portion of Saturday night.
The strong winds and cold temperatures over the relatively warm
waters will likely result in a freezing spray threat.

Winds drop below gale relatively quickly Sunday...and
remain relatively light into Monday.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory until 6 am EST Friday for anz530>534-
537>543.
Small Craft Advisory from 6 PM Friday to 6 am EST Saturday for
anz530>543.
Small Craft Advisory until 8 PM EST this evening for anz535-
536.

&&

$$
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short term...ads
long term...dfh
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marine...ads/dfh

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