Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 211353
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
953 AM EDT Fri Apr 21 2017

.SYNOPSIS...
A cold front will approach from the northwest today, pushing
across the area late today and tonight. The front will stall
across North Carolina and offshore Saturday through Sunday. Low
pressure will track eastward along the frontal boundary across
Tennessee and into the Carolinas Saturday through Sunday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Nearly full sun with temps quickly rising through the 70s
ahead of a cold front in late April. Interesting.

Latest MSAS showing the main cold front still west of the mts
with a sfc trof located ivof the Ches Bay. Sct shwr activity
well ahead of the front just now making it into the extreme nwrn
zones with mstly sunny skies elsewhere. Temps will quickly rise
above 80 over the next few hrs and max out between 85-90.

High res data indicating sct convection possible across nrn
most zones through early afternoon but nothing of concern. Data
then shows a more organized area/line of convection ahead of the
cold front entering the piedmont around 20Z, tracking ese into
the early evening hours. Given the ampl heating ahead of this
front and the weak sfc trof, do expect some strong to psbl svr
storms as this line moves through. SPC has the area in a MRGNL
risk mainly for large hail/damaging wind gusts. Adjusted grids a
bit, but left pops alone for now given no threat just yet. Culd
see a few 90 degree readings later today, especially across the
sse where more sun is expected.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
The frontal boundary will sink into NC by 12Z Sat where it
becomes nearly-stationary through Sunday. At the same time, low
pressure will track eastward along the frontal boundary across
TN and into the Carolinas. Have kept a chance of showers
(30-50%) across the entire CWA Friday night as the best focus
for pcpn will be along/north of the stalled boundary. Saturday
is looking overcast as high pressure builds across the Great
Lakes/Northeast and nudges south into the Mid-Atlantic, setting
up an in-situ wedge pattern. Best chance of pcpn during Saturday
morning looks to be along/west of I-95, but spreading eastward
to the coast in the afternoon as the aforementioned sfc low
approaches from the west. Will have 30-60% PoPs (highest west)
before 18z Sat...then increasing 50-70% after 18z. The influence
of the sfc low approaching from the west in tandem with an
upper trough cutting off over the TN Valley by Sunday afternoon
will make for a wet/gloomy end to the weekend. Will have likely
to categorical pops 60-90% thru Sunday. There is the potential
for heavy rain over much of the region (1 to 2 inches),
especially later Sat thru Sun and beyond.

Lows Fri night will range from the mid 50 to mid 60s, and range
from the upper 40s to upper 50s Sat night. Highs on Sat will
range from the lower 60s N to around 70/lower 70s S. Highs on
Sun will range from the upper 50s NW to arnd 70 SE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Latest 21/00z models continue to depict unsettled conditions
for at least the first portion of the long term/Sun night
through Tue. Deep/anomalous upper low progged to be centered
along the southern Appalachians by 00z/Mon, with sfc low along
the Carolina coast and weakening sfc high pressure along the
southern New England coast. GFS/ECMWF remain in very good
agreement with the upper low continuing to dive SE through GA/SC
on Mon, while remaining as a closed low. The forecast has
trended wetter and cooler for Mon, with the potential for some
locally heavy rain all areas Sun night, and mainly over
southern and western sections for Mon. All total we could be
looking at widespread 2-3" rain amounts from Sat-Mon. Low
pressure slowly pulls offshore by Tuesday as high pressure
builds in from the NNW with drier conditions returning, but
still likely enough moisture for continued 30-40% chance PoPs E
and 20% PoPs west. Highs Mon to avg 60-65 F with mid- upper 60s
on Tue. Warmer/dry for Wed and likely turning much warmer by Thu
as the low finally will be far removed from the region and
ridging aloft begins to center off the SE coast. Lows mainly in
the 50s with highs mid 70s inland to 65-70 F near the coast Wed,
and highs 80-85 F Thu (70s near the coast).

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
Other than some locally dense fog around KSBY thru 13z, VFR
conditions are prominent with mild/SW flow in place.

A cold front over the Ohio Valley will move across the mountains
today and slowly cross the CWA this afternoon and tonight. Scattered
thunderstorms can be expected along and just ahead of the front
potentially affecting the TAF sites between 20Z-04z.

The front will stall all across NC during the weekend as a well
organized low pressure system moves eastward along the front.
This will bring widespread rain throughout the weekend with
extended periods of degraded aviation conditions. Thunderstorms
will also be possible southern portions. The chance of showers
continues Monday into Tuesday as low pressure lingers just east
of the Carolinas.

&&

.MARINE...
Latest obs reflect SW flow ~10kt over the marine area this morning.
SW Winds will gradually increase later today, as gradient gradually
tightens ahead of a cold front which approaches the waters from the
NW. Winds to avg 10-15 kt during this period with seas mainly 2-3 ft
and waves in the Bay/Rivers 1-2 ft. The front crosses the area this
evening into the overnight hours/early Saturday morning, with high
pressure building N of the region Saturday. Winds shift to N
Saturday post-frontal Saturday morning, with experimental wind probs
continue to highlight a brief 2-4 hr window where Low-end SCA
conditions will be possible Saturday morning through early afternoon
(14-18z) with the initial CAA surge. The best chance of these SCA
winds occurring continues to point towards the southern Chesapeake
Bay and into the lower James River.

Thereafter, increasing model agreement this morning with respect to
a more prolonged period of SCA from late Sat night/Sunday morning
through midweek...as surface low pressure approaches from the SW
Saturday and tracks across the region Sunday into Sunday night. GFS
has incrementally adjusted farther south toward the NAM solution
with respect to the placement of the quasi-stationary boundary, with
the ECMWF remaining a bit north, therefore indicating a brief lull
in SCA conditions on Sunday before a second, stronger surge of NNE
winds on the back side of the departing system Monday and Tuesday.
Given the deepening low pressure and resultant increasing low level
winds, expect a period of strong SCA conditions Mon aftn into
Tuesday, and the potential for low-end Gales exists, at least over
the mouth of the Chesapeake Bay/southern coastal waters during this
same late Mon/Tue period. This setup lingers into Tuesday, with
winds to gradually diminish Tuesday afternoon and night as the low
slowly pushes farther offshore. Seas to build to 6-8 ft and waves to
4-5 ft in the Bay for Mon.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.

&&

$$
SYNOPSIS...JDM
NEAR TERM...JDM
SHORT TERM...JDM/MPR
LONG TERM...LKB
AVIATION...JDM
MARINE...MAM



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