National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KAKQ 230049
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
849 PM EDT THU SEP 22 2016

.SYNOPSIS...
Low pressure along with a weak frontal boundary will remain
stalled along or just off the Southeast and Mid Atlantic coast
through Friday morning. High pressure builds over the local area
later Friday into Saturday morning. A backdoor cold front drops
across the region during Saturday. The center of high pressure
slides into southeast Canada during Sunday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Update...
Showers are diminishing across south central VA this evening as
another area of precip tries to rotate into interior NE NC. This
particular swath of light to moderate rain showers will continue
rotating into this area and is expected to remain scattered
throughout the evening and overnight hours. Isolated/embedded
thunder is possible in interior NE NC, however this minor threat
will come to an end later this evening. Otherwise, increased sky
cover the rest of tonight while temps/dewpoints are on track with
ongoing forecast.

Previous discussion (429 PM)...
Late this aftn, areas of showers continued to affect cntrl, SE,
and scntrl VA, and NE NC, with a few showers still producing
heavy downpours. Otherwise, there was a little more brightening of
the sky ovr the CWA, with even some sunshine ovr extrm Nrn/NW
counties and ovr NE NC counties. As a result, temps climbed into
the mid 70s to lower 80s most areas. Lingering low pressure and a
frontal boundary along or just off the SE and Mid Atlc coast, will
maintain the chc for at least sctd showers ovr the srn/se half of
the region this evening into Fri morning. Heavier downpours will
diminish during this evening. Lows will range fm the lower 60s to
the lower 70s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
The combination of nrn stream energy and the coastal
low/associated upr trough weakening, will finally result in
decreasing pops and rain chcs ending ovr the sse Fri into Fri
night. Will carry slight chc to low end chc pops (20-30%) acrs
srn/se areas only during Fri. Surface high pressure will build
over the region Fri night into Sat morning resulting in dry wx
everywhere. Highs on Fri will range fm the upr 70s to mid 80s.
Lows Fri night in the mid 60s to near 70. A backdoor cold front
will drop acrs the region during Sat, and the cntr of sfc hi
pressure will bld twd SE Canada by Sun morning. Will maintain dry
wx during this period, with generally a partly sunny sky on Sat.
Highs will range fm the upr 70s to lower 80s acrs most of the
area. Expect more clouds ovr the Piedmont Sat night. Lows will
range fm the mid 50s to the mid 60s.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Medium range period begins Sunday with an amplified upper level
ridge/trough pattern, the ridge axis being centered across the
TN/OH Valley with a deep trough over Atlantic Canada. This much
the GFS/ECMWf and ensembles are in good agreement with. By Monday,
the models really begin to diverge however, the GFS and GEFS mean
being much stronger than the ECMWF with an upstream trough over
the upper midwest by Mon/Tue. this would lead to more of a strong
blocking pattern that would keep the eastward progression of upper
ridge axis much slower, becoming aligned along the east coast by
late Tue/Wed. The CMC is even slower to push the upper ridge off
to the east than the GFS/GEFS. Bottom line is a lot of model
uncertainty beyond Monday. For Sunday/Mon, surface high pressure
is progged to become centered over eastern Canada with a piece of
the High ridging down into the northern mid-Atlantic states by
Monday. Deep moisture will be pushed south of the local area, but
expect more clouds than sunshine for Sunday (except over the
eastern shore where more sunshine should prevail). Have also
lingered 20% POPS for much of the area Sunday, shifting to the SW
and far W zones Sun night/Mon. Highs will average in the low-mid
70s with lows in the upper 50s to mid 60s Sun/Mon. Did more a
broad-brushed 20% POP by late Tue-Thu as high pressure becomes
centered somewhere off the NE/northern mid-Atlantic coast and
deeper moisture and a slow moving front gradually approach from
the W. Highs will avg 75-80 F Tue-Thu with lows mainly in the
60-65 F range.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
Low pressure continues to sit off the South Carolina coast, bringing
the region unsettled conditions. Abundant low level moisture and
onshore flow will promote widespread IFR stratus...especially in the
southeast (PHF ORF ECG) with some IFR vsby. This will be slow to
improve Friday morning. Precipitation is diminishing but will still
be possible southeast portions...especially at ECG.

More favorable conditions are expected by midday Friday with VFR
conditions and mainly dry weather across the area as the
aforementioned low weakens.

OUTLOOK...A cold front sags south through the Mid Atlantic States
durIng the weekend. High pressure builds from the north but
weakens toward midweek. It will be mainly dry through the outlook
period and despite an onshore flow...VFR conditions are expected
to dominate.
-- End Changed Discussion --

&&

.MARINE...
Latest obs reflect ENE flow across the waters as Pressure
gradient remains compressed between high pressure well north into
New England and weakening low pressure lingering along/just off
the SE coast. Seas have dropped off to 4 ft or less for NC waters
so have cancelled the SCA headline there (remaining in effect for
the rest of the coastal waters and mouth of the Bay). Winds of 15kt
gradually drop off from late this aftn through tonight as
pressure gradient slackens a bit further.

Winds turn more northerly and pick up a bit by Fri night as weak low
finally nudges offshore. A weak Cold front drops across the waters
late Friday Night into Saturday, stalling just south of the waters
Sat night and Sunday before sliding south into the Carolinas on
Monday. CAA surge behind the front appears minimal...but SCA for
hazardous seas possible over the weekend as longer period swell
begins to mix in Friday night through Sunday.

&&

.HYDROLOGY...
The Cashie River at Windsor crested at 15.0 ft late this
morning...with the most current level at 14.5 ft and slowly
falling as of 715 PM this evening. This water level is still
within major flood stage, which begins at 13 ft. Although light
rain showers are expected to continue overnight through Friday
afternoon before ending, the Cashie River near Windsor is forecast
to steadily fall over the next several days...possibly dropping
below flood stage completely by roughly Sunday afternoon.

&&

.TIDES/COASTAL FLOODING...
As of 17Z, tidal departures continue to avg +0.5 to 1.0 ft over
the marine area, but no tidal flooding is occurring and no
advisories are needed at this time. Will continue to monitor
however, as tidal anomalies may build nwd through the Bay by later
this aftn which could lead to some marginal tidal flooding by this
evening farther up into the Bay.

Moderate risk for Rips expected for Thu.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 10 AM EDT Friday for ANZ650-652-654.
     Small Craft Advisory until midnight EDT tonight for ANZ634-656.

&&

$$
SYNOPSIS...TMG
NEAR TERM...BMD/TMG
SHORT TERM...JDM/TMG
LONG TERM...LKB
AVIATION...LSA
MARINE...LKB
HYDROLOGY...
TIDES/COASTAL FLOODING...