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Area forecast discussion 
National Weather Service Wakefield Virginia
1254 PM EST Sat Dec 3 2016

Synopsis...
high pressure slowly builds into the mid Atlantic through Sunday.
Low pressure passes south of the region Sunday night into Monday.
Another low pressure system crosses the region Tuesday.

&&

Near term /through tonight/...
current forecast on track with only minor adjustments made this
morning. Adjusted sky grids a bit to account for the cirrus that is
quickly spreading in from the west. Otw, mstly sunny with highs
within a few degrees of 50.

Pvs dscn:
latest wx analysis features 1028+mb sfc high pressure over the
mid-Mississippi River valley into the western Ohio River valley
this morning. Aloft, main feature of note is amplifying upper low
dropping from Southern California into northwest Mexico.
Downstream quasi-zonal flow is noted over the mid-Atlantic and
southeast this morning as low amplitude upper ridging spreads east
ahead of this system. This flow allowed some persistent mid to
high clouds (mainly a thin cirrus deck) to spread from the western
Carolinas into southern sections of the local area earlier this
morning. These clouds have thinned a bit further as depicted by
ncar ensembles and hi-res models agree in clearing sky out by
around/just after sunrise, and have gone with this trend in the
digital db.

For today, continued mild and dry weather across the region
W/sfc high pressure pushing east toward the local area under
quasi-zonal flow aloft. Look for maxima to rise mainly in the
low/mid 50s areawide under a mainly sunny sky.

Clouds then increase through the night tonight into early sun
ahead of the low pressure system to the west. Low temps tonight
mainly in the low/mid 30s and high temps sun in the upr 40s to
lwr 50s.

&&

Short term /Sunday through Tuesday night/...
pattern takes a turn towards a more active setup for the early
to mid-week period of the week ahead. Rain chances will
gradually increase later Sunday, and linger through much of the
period.

The first spoke of shortwave energy emanating from the
southern stream trough will push northeast across the area late
Sunday...as developing sfc low pressure takes shape over the Gulf
Coast region. Look for top-down moistening to continue, with
increasing clouds holding down highs by a few degrees tomorrow
vice today's highs, even as sfc high pressure lingers over the
mid- Atlantic coast. Highs in the u40s to low 50s.

By Sunday night, increasing isentropic lift will bring rain
chances,first to the US-58 corridor, eventually spreading NE to
Metro Richmond and the lower Eastern Shore by near or just after
midnight. Quantitative precipitation forecast averaging around a quarter of an inch inland to
near a half inch southeast, but even this moisture will serve to
sharpen in-situ cad wedge over the Piedmont. Lows Sunday night
not as cold with increasing clouds and pcpn moving in
late...upper 30s to low 40s.

Support for pcpn pushes east of the area Monday morning with
weak ridging seen during the afternoon as sfc high pressure
nudges offshore. Thus, maintained trend of lingering clouds and
morning rain over coastal sections. Highs in the low-mid 50s.

Tuesday appears to be the wettest of the period over the local
area. Despite some differences, GFS/ukm/ECMWF all similar in
their depiction of double barreled low pressure lifting toward
the mid- Atlantic Tuesday aftn and night.Rain looks to move in
again from SW to NE on Tuesday morning through the aftn. Upshot
here is that copious amounts of moisture will override the cooler
air at the surface to allow a cool but mainly stratiform rainfall
across the area from about 06z tues to 00z Wed. Pcpn may become
more convective across the southeast but will all depend on the location
of the front. Another lull seems to be favored Tuesday night as
the system lifts toward the northeast.

Did drop temperatures inland on Tuesday with the cool air wedge
hanging tough inland as pcpn continues. Along the coast, forecast
is a bit tougher, with models still struggling with location of
the coastal front. Case in point...the Euro ensembles varying by
5-7 std deviations for temperatures at most locations across the
southeast coast on Tuesday. Have sharpened the thermal gradient for
highs, as is typical with entrenched cad setup in place. Nudged
highs up to around 60 along the coast, with highs only in the
lower to middle 40s Piedmont sections and l-M 50s I-95 corridor.

&&

Long term /Wednesday through Saturday/...
lingering trofiness keeps residual moisture across the area Wed with
low chc pops east of i95 Wed. Seasonable with highs 55-60. Lows mid
30s to mid 40s.

An anomalous upper level trough digs across the central US Thursday
and into the eastern US Friday. A quick moving cold front progged to
push across the region Thursday, ushering in the coldest air mass of
the season. Numerical and statistical guidance still indicating a
large spread of temperatures Thursday ahead of the front (depending
on the frontal timing), so have opted to follow the lowering mean
into the low to mid 50's Thursday. Limited moisture return and
westerly flow will limit precipitation chances Thursday and Thursday
night, but will keep mention of slight chance pops for the northwest
Piedmont to the Maryland Eastern Shore. As impressive
dynamics/height falls reach the local area Thursday night, might not
be able to rule out some flurries across the northeast as strong
cold air advection combines with lingering mid level moisture. Lows
drop into the mid/upper 20's inland to low 30's near the coast. A
cool/breezy/sunny/dry day forecast Friday as the latest gefs
indicates 850mb temperatures around -10 to -12c (-2 Standard
deviations). Highs are expected to warm only into the low 40's
(upper 30's possible piedmont). Add in a breezy northwest wind and
wind chills may only warm into the 30's. Dewpoints in the teens will
allow temperatures to drop into the 20's (teens possible inland if
trends continue) Friday night under a clear sky. 850mb temperatures
progged to warm to around -6 to -8 based on the latest ensemble
guidance (still -1 Standard deviation). Surface high pressure builds
across the southeast, resulting in less mixing and temperatures only
warming to around 40.

&&

Aviation /18z Saturday through Thursday/...
VFR conditions prevail across the region with generally northwest-north winds
less than 10 kt. Some gustiness to 20 kt is occurring across the
Eastern Shore region. High pressure builds in from the west
through the weekend leading to continued dry weather. Scattered
mid to high clouds are possible across northern sections from ric
to sby this evening, with any cloud bases generally to remain
above 6000 feet.

Outlook: clouds will begin to increase late tonight and into
Sunday. The next chance for showers arrives Sunday night, with
rain likely into Tuesday with periodic visibility restrictions
and MVFR conditions Tuesday afternoon and night.

&&

Marine...
latest surface analysis centers ~990mb low pressure off the Canadian
maritime with ~1029mb high pressure over the Midwest. The result is
a northwest wind of 15 to 25 knots over the local waters early this
morning. Waves generally 2-4 feet and seas 3-5 feet. The pressure
gradient relaxes over the Lower Bay and southern coastal waters late
morning/early afternoon as high pressure builds southeastward over
the Carolinas. Northwest winds diminish to 10-20 knots in the
southern waters this afternoon, but remain 15 to 25 knots in the
northern waters. Have maintained Small Craft Advisory headlines for the southern
waters through 1pm (seas subside to 3-4 feet), and have extended the
northern waters through this evening. Seas in the northern waters 4-
5 feet. Sub-Small Craft Advisory conditions return to the waters late tonight as high
pressure centers over the mid-Atlantic region. High pressure centers
over the waters Sunday with winds diminishing to at or below 10
knots. Waves 1-2 feet and seas 2 feet. High pressure slides offshore
Sunday night and Monday, but a ridge remains over the waters as a
coastal front aligns along the southeast coast. Flow becomes
southerly Sunday night, and then northwesterly late Monday and
Monday night as high pressure builds over the Ohio Valley. Speeds
remain at or below 15 knots. High pressure builds over the northeast
Tuesday as low pressure slowly lifts along the stalled southeast
coastal trough. Flow becomes onshore at 10-20 knots, with seas
building to0 4-6 feet late Tuesday and Tuesday night. Waves build to
2-4 feet in the Lower Bay. Low pressure lifts off the mid-Atlantic
coast Wednesday with northwest flow Wednesday night. A strong cold
front Thursday will usher in the coldest and driest air mass of the
season Thursday night through Friday night. Strong Small Craft Advisory (or even
gale) conditions are possible.

&&

Akq watches/warnings/advisories...
Maryland...none.
NC...none.
Virginia...none.
Marine...Small Craft Advisory until 4 PM EST this afternoon for anz632-
634-654-656-658.
Small Craft Advisory until 1 am EST Sunday for anz630-631-650-
652.

&&

$$
Synopsis...mam
near term...mpr/mam
short term...mam
long term...mpr
aviation...mam/jef
marine...Sam

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