Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 230844
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
444 AM EDT Wed Aug 23 2017

.SYNOPSIS...
A cold front will cross the area this afternoon through tonight,
with strong high pressure building north of the area from
Thursday into the upcoming weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Early this morning, a cold front was moving thru nrn and wrn
VA. The front will push acrs the region this aftn thru tonight.
Shearing vort lobe progged to ride along the front, as winds
increase aloft. The added forcing along the boundary along with
a narrow ribbon of high precipitable waters, will result in
sctd to numerous showers and tstms this aftn and evening.
Downslope flow from 1-3km will limit the coverage over the
Piedmont, but hi-res and course resolution guidance still indicates
that the activity should become more organized fm central VA
east-southeast over the rest of the CWA, as it interacts with a
moderately unstable air mass (mixed-layer CAPE values 500-1500
J/kg) and marginal shear (25-30 knots). Dry mid levels and an
inverted V sounding indicate the main threat will be damaging
winds and frequent lightning. SPC maintains a marginal risk for
severe weather acrs scntrl and SE VA and NE NC. Heavy rainfall
is also possible, as the cold front slows as it reaches SE VA
and NE NC later this aftn and evening, due to weak waves of low
pressure moving along it. Precipitable water values progged
around 2 to 2.25 inches. Westerly flow in the mid levels
indicates that the motion should prevent widespread heavy
rainfall, but some areas could see periods of heavy rainfall.
Flow becomes north to northeast behind the front, as drier air
starts to spread into the area from the northwest later this
aftn into tonight. Warm and humid in advance of the front, with
highs today ranging fm the mid 80s to near 90.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
The front and waves of low pressure will push SE of the region
and offshore overnight thru Thu. Those waves of low pressure
will maintain slgt chc to chc Pops over extrm SE VA and NE NC.
Lows tonight will range fm the lower 60s extrm NW counties, to
the lower 70s extrm SE VA and NE NC.

High pressure will slowly build in from the northwest Thu thru
Fri, with the front getting pushed well SE of the area off the
SE coast. This will result in dry, cooler and less humid
conditions for Thu night thru Fri. Highs on Thu in the lower
80s under a partly sunny sky. Lows Thu night in the 60s. Highs
on Fri in the upper 70s to lower 80s under a partly to mostly
sunny sky.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Cooler and drier for the most of the extended period, as high
pressure builds acrs the Great Lakes and New England Fri night
thru Mon, and ridges southward into the region. Low pressure
moving NNE off the SE coast could affect the area on Tue.

Medium range guidance in relatively good agreement with developing a
tropical system along and offshore of the southeast coast along the
old frontal boundary early next week. Kept weekend dry, with low
rain chances along the SE coast by Monday. Looking ahead, rain
chances look to improve into the middle of next week, with moisture
from the remnants of Harvey looming to the SW. For temperatures,
high temperatures Sat-Mon will be at or just slightly below
normal through the period, mainly in the upper 70s to low 80s.
Early morning lows in the 50s inland to mid 60s along the coast.

&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
Early this morning, a cold front was moving into nrn/NW
portions of the CWA. That front will slowly push SE acrs the
region and off the coast today into Thu morning. Flight
restrictions will be possible along and behind the front this
aftn into Thu morning fm showers and tstms. The front should
push SE of NE NC during Thu, with lingering showers possible
over extrm SE VA/NE NC. Conditions are expected to improve
Thu aftn thru Fri, as the front shifts farther SE and high
pressure builds north of the region. Breezy NE winds expected
near the coast Thu and Fri.

&&

.MARINE...
A cold front will approach the waters from the northwest and
cross the area late this aftn through tonight. SW flow still
avearges 15-20 kt over the Bay and coastal waters, have the SCA
headlines through 7 am for the entire Bay and for the nrn coatl
waters. Waves avg 2 to 3 feet in the bay and seas acrs the N are
4-5 ft. Winds shift to the N/NE 10 to 15 knots behind the front
by late this morning N and by aftn farther S (and with
convection this aftn winds will be locally much stronger but
this will be handled w/ MWS/SMW`s as needed).

Strong high pressure builds north of the region Thursday and
into the weekend. Given the warm waters and some cold advection
late tonight/Thu morning, expect a marginal SCA event over at
least some of the Bay and probably the lower James Thu morning.
Did not raise any SCA headlines as this will be mainly a 3rd
period event (and still fairly marginal). Otherwise expect
diminishing winds later Thu aftn through Fri as sfc high
pressure builds a little farther south and the pressure gradient
weakens. Waves in the lower Bay may briefly build to 3-4 ft Thu
morning, then will subside to 1-2 ft with coastal seas 3-4 ft.

Onshore (E-NE) flow for the weekend as high pressure builds NNW
of the local area and then shifts east to New England. Winds
remain elevated 10 to 15, occasional gusts to ~20 kt Sat, and
then increase more significantly Sunday into next week as
stalled front to the south lifts back N with low pressure
developing along the boundary. Seas remain choppy Sat, and then
will build to 5-7 ft or greater late Sun into next week.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 7 AM EDT this morning for
     ANZ630>632-634-650-652.

&&

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



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