Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 232004
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
404 PM EDT Wed Aug 23 2017

.SYNOPSIS...
A cold front drops south of the area tonight, stalling along the
Southeast coast. Strong high pressure builds into the Northeast
Thursday and Friday, and remains centered over the Northeast
through early next week. Low pressure lifts offshore Monday
into Tuesday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Latest surface analysis places the cold front over northeast
North Carolina. Scattered to numerous showers and thunderstorms
have developed along and just behind the frontal boundary. A
warm, humid, and unstable air mass exists across southeast
Virginia and northeast North Carolina ahead of the area of
showers and thunderstorms. RAP/SPC analysis indicates mixed-
layer CAPE values of 1500-2500 J/kg, where temperatures are
still in the mid to upper 80`s with dewpoints in the mid to
upper 70`s. Shear remains marginal, around 25-30 knots, which is
enough for at least some organization and stronger storms. Main
threat remains locally damaging winds. Another concern will be
along the coast as the front slows and better upper level
support arrives. Impressive omega along the front with
precipitable waters in excess of 2 inches and MBE vectors at or
below 10 knots will result in locally heavy rainfall. Flash
flood guidance across the southeast is around 2-3 inches, but
given the overall progressive nature of the system, do not
anticipate widespread impacts from flooding. Headlines are not
anticipated.

Flow becomes north to northeast behind the front, as drier air
starts to spread into the area from the northwest later this
afternoon into tonight. Guidance indicates some linger moisture
over the Piedmont into central Virginia behind the front as
another area of convergence could result in additional showers
into this evening. Have increased cloud cover inland late today
through this evening and lingered chance PoPs inland through the
evening hours. Showers/thunderstorms diminish along the coast
through the evening as instability wanes and the shortwave
pushes offshore. Low tonight generally in the low to mid 60`s
northwest to low 70`s southeast.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Potent shortwave digs over the Great Lakes into the Ohio Valley
Thursday as the old cold front settles along the Southeast
coast. Height falls ahead of the shortwave will induce waves of
low pressure along the front, keeping low chance PoPs across
southeast Virginia and northeast North Carolina. North to
northeast flow will keep sky conditions generally mostly cloudy
along the coast to partly cloudy inland. Cooler and less humid,
with highs in the low to mid 80`s. Trough axis slides north of
the region Thursday night, along with the deepest moisture and
best chances for measurable precip. Have trended toward warmer
guidance Thursday night due to likelihood of cloud cover. Lows
in the low to mid 60`s. Upper 60`s near the coast.

Onshore flow persists Friday, as model soundings indicate
lingering low level moisture. Perturbations in the fast west to
northwest flow along with convergence near the coast will result
in a slight chance PoP Friday afternoon. Some modest instability
is indicated, but will keep only shower wording due to stable
onshore flow. Sky again averages partly cloudy to mostly cloudy.
Highs in the low 80`s. Partly cloudy to cloudy Friday night as
high pressure builds north of the region. Lows generally in the
low to mid 60`s. Some locales in the Piedmont forecast to drop
into the upper 50`s.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
High pressure builds from the Great Lakes across the
Saint Lawrence Valley and into New England Friday through Sunday
bringing mild and mainly dry conditions. Highs Friday through Sunday
will generally be in the upper 70s to low 80s with lows in the upper
50s to low 60s, and mid/upper 60s at the coast. Low pressure
(potentially tropical) eventually develops along a stalled frontal
boundary off the Carolina Coast early next week. This could
potentially bring some moisture into the region in the Monday-
Wednesday timeframe, but PoPs are only 20-30% at this time. Expect a
modestly strong ENE wind along the coast with strong high pressure N
of the region and developing low pressure off the Carolina Coast.
High temperatures Monday through Wednesday remain in the upper 70s
to low 80s, with lows ranging through the 60s.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
A cold front is pushing across the local area to begin the 18Z
TAF period. Behind the front, scattered to numerous showers and
thunderstorms are developing across the Piedmont into central
Virginia in a warm, moist, and unstable air mass. Showers and
thunderstorms will push eastward through this evening, becoming
better organized across central and eastern Virginia. Locally
damaging winds, heavy rainfall, and frequent lightning are the
main threats. The front pushes offshore and south of the region
tonight, with lingering chances for showers along the coast.
Flight restrictions are possible under the strongest storms.
MVFR ceilings are possible across southern Virginia and
northeast North Carolina tonight. Wind becomes north to
northeast behind the front, generally at or below 10 knots.

High pressure builds in from the northwest on Thursday as the
front stalls along the Southeast coast. An uptick in northeast
winds is anticipated Thursday morning with a surge of cold
advection, but winds diminish mid to late morning. Flow also
results in broken to overcast skies near the coast Thursday with
lingering chances for showers across the far southeast.

High pressure slowly builds north of the region through
Saturday, with periods of clouds due to onshore flow. Winds
remain northeast.

&&

.MARINE...
A cold front will push across the Mid-Atlantic coast late
this aftn and evening bringing numerous showers/tstms. The wind will
generally become NE 10 to 15kt behind the front. However, some
locally stronger wind is expected along with and in the wake of
tstms. Later tonight, high pressure will build in from the NNW and
this will result in a shallow CAA surge late tonight into Thursday
morning, which should produce a ~6hr period of low-end SCA
conditions in the Bay/lower James. Expect a NE wind to increase to
15-20kt in these locations. The duration of the wind is not expected
to be long enough to build seas to 5ft in the ocean. SCA flags have
been raised for the Bay/Lower James for late tonight into Thursday
morning. The wind should diminish and remain NE later Thursday aftn
into Friday as high pressure builds into the region. Seas should
subside from 3-4ft to 2-3ft, with 1-2ft waves in the Bay.

Onshore (ENE) flow should continue through the weekend as strong
high pressure builds N of the region across New England. The wind
should remain elevated Saturday, 10-15kt/15-20kt ocean, and then
increase more significantly Sunday into Monday as low pressure
develops along a stalled frontal boundary to our S and then
gradually lifts nwd. The wind increases to 15-20kt/20-25kt ocean
(potentially 25-30kt S of Cape Charles). Seas initially build to 3-
5ft Saturday, then 5-7ft Sunday, and potentially 6-10ft by Monday.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory from 1 AM to 1 PM EDT Thursday for ANZ632-
     634.
     Small Craft Advisory from 4 AM to 1 PM EDT Thursday for ANZ638.
     Small Craft Advisory from 1 AM to 10 AM EDT Thursday for
     ANZ630-631.

&&

$$
SYNOPSIS...SAM/TMG
NEAR TERM...SAM
SHORT TERM...SAM
LONG TERM...AJZ
AVIATION...SAM/TMG
MARINE...AJZ



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