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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KAKQ 240831
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
431 AM EDT SAT SEP 24 2016

.SYNOPSIS...
-- Changed Discussion --
A backdoor cold front drops south across the region today. High
pressure tracks across Southeast Canada early next week. A second,
stronger cold front will cross the region later Tuesday.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
Latest analysis features strong 1026+mb high pressure over Ontario
into the Upper Great Lakes. Subjective wx analysis places weak
cool frontal boundary from Southern New Jersey back into the
Mason-Dixon line and the lower Ohio Valley early this morning.
Meanwhile, weak ~1018mb high pressure is in place across the
region. Aloft, prominent upper level ridging remains in place,
centered across the mid-south and Mississippi River Valley. this
is keeping PW values suppressed in the 1-1.25" range across the
region per early morning Blended TPW sat product.

Have noted some areas of ground fog, dense in spots along the
southern tier of the forecast area. Will likely have to handle
with a round of targeted statements this morning, but otherwise
expect fog and any lingering stratus to get mixed out quickly
after sunrise this morning. After fog scours out, expect a partly
to mostly sunny start, with clouds quickly increasing across the
northern tier of counties from Late Morning through the aftn as the
front drops across the area. Winds shift to the N-NE during this
timeframe. High-res models resolute in showing an area of rather
shallow lift along the front as it drops across the southern half
of the area from late aftn through about midnight. Have
accordingly kept the forecast dry through the day, introducing
some sct showers tonight, mainly across the piedmont and I-85
corridor. QPF will be minimal with still relatively dry air aloft.
and only weak isentropic lift. Thickness tools and CONShort/HRRR
basically identical wrt high temps, producing highs in the mid to
upr 70s eastern shore...low to mid 80s RIC metro...and mid to
upper 80s far SW zones.

Front drops south of the area late tonight, with sct showers
along the boundary likely lingering into the morning hours. Clouds
will be on the increase post-frontal, especially inland with post
frontal nne flow as high pressure ridges down and cool air wedge
begins to set up. Accordingly beefed up sky cover tonight and into
Sunday. Lows Sat night in the mid 50s north to mid 60s south.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
-- Changed Discussion --
Front continues to push south into the Carolinas Sunday in
response to high pressure sliding across Southeast Canada. This
high extends south across the Mid Atlantic Region Sunday and
Sunday night. Have again increased SKY cover to account for
increasing low level moisture/ongoing weak isentropic upglide.
Overcast conditions and pockets of light rain or drizzle remain a
good bet along and west of the I-95 corridor. Pops remain only in
slight chc range with minimal chances for measuring pcpn.
Nonetheless, drizzly and overcast inland...a mix of some sun along
with clouds along the coast. Highs Sun 70-75. Lows Sun night in
the mid 50s to lwr 60s. Cooler readings in the lower 50s with
clearing sky across Eastern shore.

Upper ridge pivots to the coast on Monday, before sliding offshore
Monday night. At the sfc, high pressure moves north of New
England Monday with the next front approaching from the west
during the afternoon. Across the piedmont, cool air wedge will
hold on one more day...with lingering clouds, onshore flow
maintaining cool temps. Monday highs generally in the low to mid
70s, upper 70s to around 80 along the SE coast.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Strong cold front progged to drop into the region Monday night ahead
of a potent northern stream trough. Latest deterministic and
ensemble guidance in good agreement with pushing the front across
the region late Monday night through Tuesday. Moisture increases
along the front with precipitable waters climbing above 1.75 inches.
Instability progged to be marginal ahead of the front due to cloud
cover and poor lapse rates, However, will keep mention of slight
chance thunder in the area of highest showalter values (elevated
instability) and shear around 40 knots. Both GFS and ECMWF models
push the front across the region rather quickly Tuesday with much of
the area seeing a decent chance for shower. Have capped at high end
chance. High pressure builds in from the west late Tuesday and
Tuesday night. Will linger POPs over the southeast half of the
forecast area, but expect much of the precip to push offshore by
late Tuesday night. High pressure prevails through the end of the
week and into the weekend.

Temperatures will average close to seasonable averages, with highs
Tuesday ranging from the mid 70`s northwest to around 80 southeast.
Highs Wednesday through Friday generally in the 70`s with lows in
the 50`s, expect in the 60`s southeast. Based on the latest
statistical guidance, the Piedmont may see some readings in the
40`s Thursday morning.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
Mostly clear skies this morning as weak high pressure slides over
the area. Given light winds and still wet grounds, noting areas
of low Stratus/fog across the SE coastal plain, impacting KECG,
and eventually KSBY and KPHF after 08z. Expected low clouds/fog
will scour out quickly after sunrise this morning, improving
quickly from LIFR/IFR at ECG to MVFR/VFR after 14z.

Thereafter, primarily VFR conditions expected. A backdoor cold
front drops across the area through the day Saturday...primarily
spreading widespread high clouds across the area during the day.
Given the abundant/recent rainfall from the past several days and
persistent onshore/ne winds, expect SCT cumulus to develop during
the aftn...especially near coastal sites. KSBY will likely
experience MVFR cigs given frontal timing, and Hi-res models
continue to support VFR farther inland. Could see some Sct showers
west of KRIC after 21z this aftn, but minimal support for pcpn at
terminals with plenty of dry air in place aloft.

The front pushes south of Albemarle Sound after midnight Saturday
night with stronger central high pressure sliding across Southeast
Canada and building down into the Mid Atlantic Region through
Sunday night before sliding off the New England coast early next
week. Areas of fog and some low stratus expected once again across
the southern terminals late Tonight into early Sunday morning.

Outlook...
Cigs trend back toward VFR for most locales along the coast as
cool air wedge sets up across the piedmont. Lingering low
clouds/light rain possible at KRIC and west.

&&

.MARINE...
Weak pressure gradient observed over the waters early this morning
as a cold front drops into the northern Mid-Atlantic region. Winds
are generally out of the west-southwest at or below 10 knots. Seas 3-
4 feet and waves 1-2 feet. The weak front drops southward over the
waters today, with flow becoming northernly. 850mb temps dip
slightly behind the front, but a lack of low level cold air
advection and weak gradient winds expected to keep winds sub-SCA
this afternoon. Hi-resolution guidance has trended lower on speeds
as well. Waves build to 2-3 feet late morning/early afternoon. For
the coastal water, distant tropical cyclone Karl will aid in
building seas to 4-5 feet this afternoon through tonight. Have
raised SCA headlines for all coastal waters as a result. Expect a
few gusts to around 20 knots, so have opted against SCA for
hazardous seas. High pressure builds southward over the waters
tonight, with northernly winds diminishing to around 10-15 knots.
Seas subside to 3-4 feet Sunday afternoon. Waves 1-2 feet.

The next cold front approaching from the northwest will shift winds
back to the south to southeast Monday. Marginal southerly SCA
conditions are possible ahead of the front late Monday and Monday
night behind a lifting warm front. The front progged to reach the
waters Tuesday morning, pushing offshore Tuesday afternoon. SCA
conditions expected behind the front as a significantly cooler air
mass and strong high pressure builds in from the northwest.

&&

.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 late Sunday night. See FLSAKQ for details.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory from 1 PM this afternoon to 10 AM EDT
     Sunday for ANZ650-652-654-656-658.

&&

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