Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 242254
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
654 PM EDT SAT SEP 24 2016

.SYNOPSIS...
A backdoor cold front settles across the Carolinas tonight. High
pressure tracks across Southeast Canada Sunday and Monday. A
second and stronger cold front will cross the region Tuesday.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Mid afternoon MSAS/sfc obs has the backdoor front ivof I64 with a
1025mb high centered south of James Bay. Models show this high
will be strong enough to push the frontal boundary into North
Carolina and south of the Albemarle Sound after 00Z. ST thickens
due to the post-frontal NNE flow allowing a wedge to setup. High
res data showing just enuf support for a few showers with the
front this evening (given crnt temps arnd 90) and some spotty
light rain/sprinkles behind the boundary across the piedmont
after midnite. Lows in the mid 50s north to mid 60s south...
except upr 60s sern coastal areas.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Front pushes south to near the NC/SC border Sunday in response to
high pressure sliding across Southeast Canada. This high extends
south across the Mid Atlantic Region Sunday and Sunday night. Per
TSCTNS, have maintained mstly cldy conditions west of the Ches Bay
to account for low level moisture/weak isentropic upglide. Of note
is somewhat drier air progged to work its way south along the
eastern shore Sun. This will allow for skies to become pt sunny
there. Overcast conditions and pockets of light rain or drizzle
are possible along and west of I95. Pops remain only in slight chc
range with minimal chances for measuring pcpn. Highs Sun in the
low to mid 70s. Lows Sun night in the mid 50s to lwr 60s except
50-55 with clearing skies across Eastern shore.

High pressure moves north of New England Monday with the next front
approaching from the mts during the afternoon. Cool air wedge holds
firm across the piedmont resulting in another mstly cldy day with
highs in the mid to upr 70s.

A strong cold front progged to drop into the region late Monday
night ahead of a potent northern stream trough. Latest data shows
the front slowing a bit as it pushes across the region Tuesday.
Moisture increases along the front with PW`s climbing above 1.75
inches along with marginal instab. Pcpn enters the region from the
NW with highest pops after midnight. Lows Mon nite in the mid 60s.

Models show possible weak s/w energy riding east along the boundary
Tuesday. This will likely enhance pcpn and allow it to linger a bit
longer especially along coastal sections. Thus, went ahead and
bumped up pops to likely across the sern zones. Kept thunder chcs in
as well. Highs Tuesday in the low to mid 70s. QPF generally between
1/2 to 3/4 inch.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Will stay closer to the 12z GFS for the extended period. Cold
front pushes off the coast Tue ngt, and will linger just offshr
thru Thu until nrn stream upr trough drops se fm the Great Lakes
and ewrd acrs the NE U.S. So, will have chc pops (25-40%) ovr the
ESE counties Tue ngt and Wed, slgt chc pops ovr ESE counties Wed
ngt, and 10-14% pops entire area Thu. Large sfc high pressure area
will then bld into and ovr the region Thu ngt thru Sat, providing
dry/comfortable early autumn conditions. Temperatures will
average close to seasonable averages, with highs Tuesday ranging
from the mid 70`s northwest to around 80 southeast. Highs Wed thru
Sat generally in the 70`s with lows ranging thru the 50s into the
lower 60s.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Backdoor cold front moving south across the region this afternoon.
Wind shift to the north well ahead of it, but the boundary is
denoted by a BKN-OVC ST layer between 1.5-2.5K ft. This cloud
deck will lift a bit (btwn 3-4K ft) as it drifts south across the
region over the next several hours. The MVFR conditions along with
NNE winds at 10 mph or less continue through most of the forecast
period west of the Ches Bay. Model data indicating drier air from
the north begins to work its way south along the Delmarva late
tonight with SCT-BKN cloud coverage. Latest data continues to
support VFR conditions at SBY after 12Z Sun.

A light shwr/sprnkl possible at RIC tonite as the wedge sets up,
but coverage not widespread enuf to include in forecast attm. Fog
not expected to be an issue tonight, but local MVFR VSBYS (3-5SM)
possible towards sunrise.

Outlook...
The next chc for sgnfcnt pcpn comes late Monday night and Tuesday
ahead and along the next cold front.

&&

.MARINE...
7 PM UPDATE...
Added the mouth of the Chesapeake Bay for a SCA through 7 AM
Sunday morning. Seas in the coastal waters have increased to 5
ft last few hours. Expect waves in the mouth of the Bay to
increase to 4 ft shortly.

Also northeast winds have increased in the Bay and Lower James
River are occasionally gusting to 20 knots and have Marine Weather
Statement in effect until 9 PM EDT.

Previous Discussion...
Will maintain SCA for the coastal waters thru Sun morning, as NNE
winds 10 to 20 kt coupled with distant tropical cyclone Karl will
aid in building seas to 4-5 feet this evening through tonight. The
cntr of high pressure will build southward into SE Canada tonight
into Sun morningover the waters tonight, with NNE winds
diminishing to 5 15 kt. Seas will subside to 3-4 feet Sun
afternoon. Waves will bld to 1-3 feet tonight, then subside to 1
to 2 ft during Sun.

The next cold front approaching from the northwest will shift winds
back to the south to southeast Mon. Marginal southerly SCA conditions
are possible ahead of the front late Mon and Mon night behind a
lifting warm front. The front progged to reach the waters Tue
morning and aftn, pushing offshore Tue evening/night.

&&

.HYDROLOGY...
The Cashie River at Windsor continues to fall but remains in the
moderate flood range. The river is forecast to slowly fall below
flood stage Sunday evening. See FLSAKQ for details.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 7 AM EDT Sunday for ANZ634.
     Small Craft Advisory until 10 AM EDT Sunday for ANZ650-652-654-
     656-658.

&&

$$
SYNOPSIS...MPR
NEAR TERM...MPR
SHORT TERM...MPR
LONG TERM...TMG
AVIATION...MPR
MARINE...TMG/LSA
HYDROLOGY...


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