Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 052351

Area Forecast Discussion
National Weather Service Wakefield VA
651 PM EST Tue Dec 5 2017

A strong cold front crosses the area late tonight through
Wednesday, then stalls offshore through late week. Low pressure
is expected to ride northeast along this boundary late in the
week into the weekend.


Latest weather analysis features Sfc hi pressure offshore of
the northeast/Mid-Atlantic coast. To the west, an occluded
surface low now lingers across central Ontario, with the
associated strong cold front now from the interior northeast
(nrn NY/ E PA), crossing the Central and southern Appalachians
and extending down into the deep south. Rain chances still on
track to ramp up with the frontal passage, as better forcing
arrives after midnight.

The front slowly settles S and E of the local area by late
morning/midday Wed. A rather narrow line of SHRAs along and
just behind the front will cross the area Tue night into Wed
morning. PoPs 70-90% coincide w/the frontal passage into Wed
morning...then trending down NW-SE through midday. Mainly dry in
the afternoon, though any clearing will be slow and potentially
only N and W of RIC. QPF trend continues with majority of
forcing/moisture to our south. QPF averaging 1/3 to 1/2 inch.
Remaining mild tonight...then temps drop off late. Low to mid
40s out west...near 50 SE coast.


Short term forecast period characterized by the gradual
departure of the closed low over SE Canada, with the remnant
positively- tilted upper trough lingering over the eastern-third
of the CONUS through late week. Sfc boundary will remain
oriented along and just offshore Wed night-Friday, and resultant
SW flow aloft running parallel to the frontal boundary should
serve to maintain widespread cloudiness over at least the SE 1/2
of the FA through much of the period.

Most of 12z suite of models continues with the idea of ejecting
numerous weak perturbations along the baroclinic zone oriented
just offshore Thu night-Friday and again Friday afternoon-Saturday.
Should also be noted that the new 12z ECMWF has nudged a bit
slower (to the left) aloft and with its sfc track. This
represents a turn away from its 00z ensemble mean (EPS) and that
of the GEFS. Will accordingly stay the course and stick close
to previous forecast package. Rain chances taper down quickly
from late morning through the afternoon out west in the
piedmont, though have lingered a low pop SE with front likely to
slow down and become hung up along the coastal plain through
Wed aftn, thanks to dominant SW flow aloft. Partly cloudy
inland/mostly cloudy to overcast at the coast. Temps remain
nearly stable through the day before tumbling through the 40s
Wed afternoon/evening with CAA. Colder Wed night, but well-mixed
atm should hold temps up a bit. Lows upper 20s to low 30s
inland...mid 30s at the coast.

As stated previously, synoptic pattern (namely the lack of
strong surface high and necessary substantive CAA), meager
forcing and resultant weak precipitation rates will likely
result in several periods of light precipitation. The first
coming late Thursday night and Friday. A period of light
snow/snow showers is quite possible (quite a few GEFS members
would argue likely inland) Thu night into Friday. However, due
to all the issues mentioned above, continue to expect little to
no accumulation. Temperatures will nudge near or slightly below
normal for the late week period. Highs Thursday 45-50, knocking
back into the upper 30s to low 40s Friday behind a secondary
surge. Early morning lows in the upper 20s well inland to upper
30s SE coast Friday morning mid 20s to mid 30s Saturday morning.


Long term period characterized by a broad (and amplifying)
Eastern U.S. trough. In general, 12Z/05 suite of models, and
their respective ensemble means, continue to be in good
agreement with the overall setup. However, temporal/spatial
differences remain with a few weak waves of low pressure sliding
E/ESE through the region. The first of these waves moves
offshore Saturday morning, allowing for clearing during the day
Saturday, although it will be cold. Any lingering light rain or
rain/snow mix will move out of the area before noon. High
temperatures Saturday in the 40s, some 10 degrees or so below
normal. A second shortwave rotates across the region Saturday
night/Sunday, with tangible weather impacts remaining north of
the area. Cold Saturday night with temperatures most areas
dropping well into the 20s.

Flow becomes temporarily less amplified Sunday through Monday,
with a slow moderation in temperatures starting Sunday night,
under clear to partly cloudy skies. High temperatures Sunday
only in the low to mid 40s, with low temps Sunday night again
mostly in the 20s (slightly warmer near the Bay/ocean). Highs
Monday in the 40s to around 50 (SE).

Next shortwave trough amplifies the flow Monday night through
Tuesday, with the attendant Arctic cold front moving through the
area late Tuesday/Tuesday night. This front is expected to be
accompanied at least scattered showers, with enough lo level
warm air intrusion ahead of the system to keep the precipitation
mainly in liquid form. Lows Monday night in the lower 30s, with
highs Tuesday upper 40s to mid 50s (SE).


Cold front crosses the area late tonight with band of rain shwrs.
CIGS appear to be the challenging part of the forecast as they
already are hovering arnd 1K ft along the coast. Thus, started
off the forecast with IFR/MVFR CIGS then brought SHWRS / BR btwn
03Z-12Z at RIC/SBY, 06-14Z sern TAF sites.

The front stalls off the coast Wed with TSCTNS showing mid level
moisture lingering along the coast. Expect the SC cloud deck at
RIC to sct out during the aftrn. OTW, BKN-OVC SC lingers thru
the end of the forecast period. Winds become gusty btwn 15-20
KTS along the coast at times ahead of the front then right
behind it as winds turn into the north.

The frontal boundary remains S & E of the local area through
Saturday with a series of weak low pressure areas tracking NE
along it. BKN-OVC CIGS and occasional pcpn xpctd, Thu night and
Fri, then again Fri night into Saturday.


Small craft advisory, albeit very marginal, continues over the
waters this afternoon and evening ahead of a strong cold front.
Winds ahead of the front have been slow to increase today,
likely due to colder water now inhibiting mixing. Expect winds
to die off for a few hours before frontal surge begins from
north to south around 09Z. Looks like a 6 hour surge of SCA
criteria winds behind the front, before winds gradually die off
later Wednesday/Wednesday night.

West/WNW winds 10-15 kt will continue through Thu, before winds
turn northerly as low pressure develops off the southeast coast
Friday/Friday night. This low pressure area is not forecast to
intensify until it is well east of the area, which means winds
will generally remain below SCA criteria Friday through


Last of the high astronomical tides is occurring at Saxis,
Bishops Head and Cambridge this afternoon. After this high tide,
water levels are expected to slowly return to more normal
levels through Friday.


MARINE...Small Craft Advisory until 10 AM EST Wednesday for ANZ630>632-
     Small Craft Advisory until 1 PM EST Wednesday for ANZ650-652-


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