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-- Discussion containing changed information from previous version are highlighted. --
110
FXUS61 KAKQ 302213
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
613 PM EDT Fri Sep 30 2016

.SYNOPSIS...
Upper level low pressure gradually lifts north toward the
Great Lakes tonight into Saturday, with a frontal boundary pushing
across the area tonight into Saturday. The upper low then gradually
pushes northeast through the Saint Lawrence Valley Saturday night
into Sunday with drier air building into the region from the west.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
-- Changed Discussion --
The Delmarva is presently getting a much need break from
heavy rain, which has totaled up to 6-12" across DE/Lwr MD Ern Shore
over the past 48 hours. This water will result in rising main stem
rivers through the evening and potentially through at least Saturday.
Follow the latest flood warnings for more details.

Current GOES WV imagery continues to depict a stubborn anomalous
upper low over central KY. A plume of deep moisture extends from off
the SC/GA coast nwd into central NC/s-central VA, and nw across the
central Appalachians. Another plume to the east has pushed offshore
brining the need break in rain to the Delmarva.

Showers and embedded tstms are developing are streaming nwd into the
Piedmont/I-95 corridor. This activity is being triggered by the
combination of the aforementioned moist plume/mid-level theta-e
ridge, a push of mid-level dry air on the wrn flank of the moisture
stream, a spoke of shortwave energy rotating around the upper low.
The interaction of the push of dry air into the moist airmass will
create some convective instability aloft. Strong mid-level flow (55-
65kt at 500mb) will result in strong deep layer shear. This
combination could trigger some strong to marginally severe tstms
this afternoon and evening, which is reflected in the marginal
outlook from SPC. The main threats are hail and locally strong wind
gusts. The main limiting factor will be the lack of SB/BL CAPE with
an in situ wedge airmass in place. The greater threat through the
afternoon/evening will be the potential for flooding over central VA
where 1hr FFG is only 0.5-1.0" after Wednesday evenings excessive
rain. A Flash Flood Watch has been issued through midnight to
account for this. The best coverage will be from the I-95 corridor
westward through the evening.

Showers/tstms will gradually lift northeastward this evening into
early Saturday morning as the mid-level theta-e boundary lifts to
the ne. Anomalous PW values cling toward the coast through
Saturday morning. Shower/tstm coverage is not clear at this time
for the Lower Ern Shore late tonight into Saturday morning.
However, these areas are very sensitive to any additional
rainfall, so a short-term flash flood watch may be necessary
depending on the areal coverage of pcpn. Drying inland late this
evening through the overnight with some breaks in the clouds
possible over the southern Piedmont. Mild again with lows in the
mid to upper 60s.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Drier air continues to entrain into the upper low
Saturday as it fills and lifts northward, then northeastward
Saturday night through Monday. The result will be gradually
improving conditions. Addition energy lifts over the region in
southwest flow aloft, so can`t rule out iso-sct showers along the
coast Saturday aftn, with a lesser probability Sunday afternoon. Sky
conditions also improve with a partly cloudy sky inland, but
remaining mostly cloudy near the coast Saturday, before becoming
partly cloudy Sunday and Monday. Highs Saturday range from the upper
70s to low 80s, but less humid as dewpoints drop into the upper 50s
to low 60s inland. Highs Sunday and Monday will again be in the
upper 70s to low 80s, with lows in the low/mid 60s.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The long term period will see a return of an onshore flow that
prevailed during much of the past week. a stationary front will be
situated well off the Mid Atlantic Coast with a strong surface high
over southeast Canada rebuilding over the Eastern Seaboard. Upper
level ridging will slowly breakdown during the week as a strong
upper level trough moves across the Northern Great Plains.

There will be 20 to 40 percent chances for showers especially over
eastern portions of the area with highest chances Wednesday through
Thursday night.

Hurricane Matthew may influence portions of the area late in the
week. Although the track is uncertain...it is expected that its
greatest impact will be in the marine area. Check with the National
Hurricane Center for updates and details.

High temperatures are forecast to range through the 70s with Tuesday
likely being the warmest day. Low temperatures will generally be in
the 60s.

&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
The combination of low pressure over the Ohio Valley and a
stationary front from North Carolina to off the Virginia coast was
producing a moist onshore flow over the Mid Atlantic States.
Satellite showed clearing over the coastal waters and portions of
the Bay and mostly cloudy sky over the TAF sites. Occasionally where
the sky clears over southeast portions...the clouds fill back in
with a broken MVFR layer. IFR cigs were over SBY and may continue
through nearly all of the TAF period.

Thunderstorm activity was beginning to develop over far southern
Virginia and south into eastern North Carolina and was spreading
northward. With the unstable airmass in place...put VCTS for
portions of the afternoon at all the TAF sites except SBY.

IFR (and possibly LIFR) redevelops late this evening and overnight
at RIC and SBY. It may need to be added to PHF but is unlikely at
ORF and ECG. Conditions improve during the mid to late morning
Saturday.

&&

.MARINE...
Seeing a gradual downward trend in seas and waves in the mouth of
Ches Bay. Will allow SCA for the Bay to expire at 400 PM as
planned and keep remaining SCA flags unchanged with regard to
previously determined end times. Main change has been increasing
wind speeds over the waters from Fenwick Island to Chincoteague
where sustained winds range from 10-20kt with gusts to around 25kt
possible. These speeds are anticipated to diminish through this
evening.

Strong/anomalous sfc high pressure remains over sern Canada
through tonight before weakening Sat aftn. Meanwhile, stacked low
pressure over the Midwest will continue to drift north and
slightly east during this same timeframe. This will translate into
winds becoming more se through tonight and then more sly on Sat.
Speeds will generally be aob 15kt during this time. Waves on Ches
Bay will average 1-3ft tonight into Sat...while seas generally
average 4-5ft until SCA expiration times when seas will then
average 3-4ft during the same timeframe. Onshore 9-10 sec period
swell should also be anticipated tonight through Sat aftn.

Calmer marine conditions expected Sat night through Mon. Wind
directions will be variable sw-w through Sun evening and then
shift to a more nly direction Mon into early Tue. Winds are then
expected to increase in response to a tightening pressure gradient
caused by Hurricane Matthew (located off the Atlantic coast of FL)
and another Canadian high pressure centered over se Canada/nrn New
England Tue aftn into Wed night. Still a lot of uncertainty
regarding Matthew`s storm track at this time, but the general
trend will be for increasing onshore winds and continually
building seas for the second half of next week.

&&

.HYDROLOGY...
-- Changed Discussion --
River flooding is developing across the primary rivers of the
MD Lower Eastern Shore due to recent heavy rainfall, mainly the
Pocomoke and Nanticoke. This flooding will likely persist at least
through Saturday. See the latest flood warnings (FLWAKQ) for more
details.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...

-- Changed Discussion --
* Updated at 613 PM EDT. See numbered bullets below for
  additional details.

Strong/anomalous sfc high pressure remains over sern Canada
through tonight before weakening Sat aftn as stacked low pressure
over the Midwest drifts north and slightly east during this same
timeframe. This will translate into onshore/se winds through
tonight and then more southerly (and decreasing) on Sat. As the
winds shift and decrease, tidal anomalies will decrease
incrementally by a few tenths of a foot with each passing high
tide cycle.

Several areas of concern are as follows:
1. Coastal flood warning for the MD Lower Eastern Shore on Ches
Bay has been extended through 400 AM Sat morning (primarily based
on tidal data for Bishops Head). The previous warning for the Nrn
Neck has been transitioned into a coastal flood advisory and is
now in effect through 400 PM Sat aftn.

2. Coastal flood advisory for wrn Ches Bay areas from Hampton
Roads to the Middle Peninsula has been extended through 1200 PM
Sat aftn.

3. Coastal flood advisory for Maryland Beaches and Ches Bay side
of VA Eastern Shore will continue through 1100 AM Sat morning.

4. Coastal flood statement will be in effect for Virginia Beach
and Eastern Currituck this evening as tide levels end up within
0.3ft of minor flooding thresholds. Nuisance flooding may be
possible in the persistent onshore flow.

* Surf zone forecast has ended for the season.
-- End Changed Discussion --

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
MD...Coastal Flood Advisory until 11 AM EDT Saturday for MDZ024-025.
     Coastal Flood Warning until 4 AM EDT Saturday for MDZ021>023.
NC...None.
VA...Coastal Flood Advisory until noon EDT Saturday for VAZ084>086-
     095>097-523>525.
     Coastal Flood Advisory until 3 PM EDT Saturday for VAZ089-090-
     093.
     Coastal Flood Advisory until 11 AM EDT Saturday for VAZ099-100.
     Flash Flood Watch until midnight EDT tonight for VAZ064-075-
     076-081>083-511>522.
     Coastal Flood Advisory until 4 PM EDT Saturday for VAZ075>078.
MARINE...Small Craft Advisory until 10 PM EDT Saturday for ANZ650-652-
     654.
     Small Craft Advisory until midnight EDT tonight for ANZ656-658.
-- End Changed Discussion --

&&

$$
SYNOPSIS...AJZ/SAM
NEAR TERM...AJZ/SAM
SHORT TERM...AJZ/SAM
LONG TERM...LSA
AVIATION...LSA
MARINE...BMD
HYDROLOGY...ESS
TIDES/COASTAL FLOODING...BMD