Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 091140
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
640 AM EST Fri Dec 9 2016

.SYNOPSIS...
Canadian high pressure builds into the Mid-Atlantic today,
settling over the region tonight into Saturday. The high slides
offshore Sunday. Low pressure will push north of the area on
Monday, with the associated cold front crossing the region late
Monday. Another strong cold front impacts the region during the
middle of next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Latest surface analysis centers 1045+mb high pressure over
Alberta, with a ridge extending southeast into the central and
eastern portions of the US. The associated air mass has spilled
over the mountains, with dewpoints already dropping into the teens
across the forecast area. Temperatures are steadily falling as
well, with morning lows still forecast in the mid to upper 20`s.
An extension of the Arctic high will break off over the Midwest
this morning, and builds eastward into the Ohio Valley late today.
Ongoing cold air advection ahead of the building high will result
in a cold/brisk day today. 850Mb temperatures drop to around -10C
(-2 standard deviations) by this afternoon. Low level thicknesses
yield temperatures in the upper 30`s to around 40, so continue to
undercut statistical guidance. Highs forecast in the upper 30`s to
around 40 (-1 standard deviation) under a sunny sky. A brisk
northwest wind of 10-15 mph inland and 15 to 20 mph near the coast
is expected and will keep wind chill values in the low to mid 30s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
Cold, Canadian high pressure builds into the region tonight as
the mid level trough axis pushes offshore. Winds decouple away
from the coast, with temperatures dropping into the upper teens to
around 20 inland to the mid 20`s near the coast. The high finally
builds over the mountains, centering over eastern North Carolina
Saturday. 850Mb temperatures and low level thicknesses moderate
somewhat Saturday thanks to westerly flow, but limited mixing and
850mb temperatures still around -8 to -10C will still result in a
cold day. Highs similar to Friday, generally in the upper 30`s to
low 40`s under a sunny sky.

High pressure remains over the region Saturday night. Meanwhile, a
northern stream trough dives into the Great Lakes region,
resulting in increasing high clouds late. There should still be
several hours of rather ideal radiational cooling conditions with
lows again dropping into the low to mid 20`s. The initial wave
pushes north of the region Sunday with a secondary wave diving
into the Ohio Valley. The surface high slides offshore. Increasing
clouds and limited mixing will again result in below normal
temperatures. Highs generally in the mid 40`s to low 50`s
southeast.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Sfc high pressure slides offshore by Sun aftn and winds become
more sly on Sun. The combination of a weak coastal trough
developing off the Carolina Coast Sun night and a warm front
lifting north through the area should bring rain up along the Mid
Atlantic coastal areas Sun night. A cold front associated with low
pressure tracking along the St Lawrence River Valley is then
expected to cross the region Mon and exit the coast late Mon
night. Winds generally sw ahead of the front...becoming nly Tue.
The cooler air behind the cold front is much more modified and
what would be typical breezy conditions along the coast are not
anticipated at this time. Sfc high pressure returns Tue/Tue
night...followed by what could be a developing coastal low off the
Southeast into Mid Atlantic coasts on Wed.

A brief warm-up should be anticipated as the aforementioned warm
front lifts through the region Sun night into early Mon. Areas
north of the warm front should remain wedged and keep cooler air
in place prior to the initial onset of precip. This could result
in a rain/snow mix quickly transitioning to all rain overnight.
Precip should remain as rain through Monday. Temperatures
generally at to slightly below normal throughout the period.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
High pressure/fair weather expected today as cold Canadian high
pressure builds in from the west. SKC conditions prevail as the
earlier high clouds have pushes offshore. Northwest winds become
10-15 knots mid morning through the afternoon with a few gusts
around 20 knots.

OUTLOOK...High pressure builds into the area through Saturday.
High pressure slides offshore Sunday. There will be a chance for
rain Monday as a cold front approaches from the west. Following
the passage of the cold front Monday night...dry weather returns
for Tuesday.

&&

.MARINE...
High pressure continues to build into the waters this morning, but
the center of the high is still over the Central Plains. This has
left a significant pressure gradient in place with the region
sitting between this high and a strong low over The Canada
Maritimes. The Northwest flow is in place with winds of 15 to 20
kt and gust 25 to 30 kt over the Bay and coastal waters. With the
strong cold advection that remains in place through Friday
evening, the strong nw flow will continue into tonight. Once the
flow aloft becomes more westerly aloft and the cold advection
weakens along with a relaxation of the pressure gradient, expect
the winds to gradually weaken overnight Friday into Saturday. Have
left the headlines intact for now, but the SCA on the area Rivers
and also Currituck Sound maybe able to be dropped early as
conditions improve there first. With seas lagging behind the
winds, expect the SCA on the Bay and Coastal waters to continue
through Friday night.

For the weekend, the surface high will settle over the region
allowing for a quiet period with relatively light wind and seas.
By Sunday night, the sfc high slides off the coast and the flow
begins to turn southerly. The models show a 40 - 60 kt low level
jet developing ahead of cold front Sunday night. But the question
becomes will these winds mix to the surface. The effective warm
front should be near the Mason-Dixon line, however, the models
show the low level front may be a weak wedging type boundary with
a coastal front that may keep the low levels stable and the 950 mb
jet from mixing down. This low level boundary should dissipate on
Monday as the mixing improves ahead of the front, which should
then allow the winds to mix better and the potential exist for SCA
conditions just ahead of the cold frontal passage Monday and
lingering into Tuesday in the cold advection the follows the
front.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ635-
     636-638.
     Small Craft Advisory until 7 AM EST Saturday for ANZ630>632-
     634.
     Small Craft Advisory until 4 AM EST Saturday for ANZ633-650-
     652-654-656-658.

&&

$$
SYNOPSIS...AJZ/SAM
NEAR TERM...AJZ/SAM
SHORT TERM...AJZ/SAM
LONG TERM...BMD
AVIATION...SAM/LSA
MARINE...ESS


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