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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KAKQ 010604
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
204 AM EDT Sat Oct 1 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 8 AM THIS MORNING/...
Updated grids per current radar and sfc ob trends. Basically
increased pops across the piedmont as addntl showers keep dvlpng
with the high res data suggesting these last through 10-12Z. Chc
pops elsewhere. Pcpn off the coast appears to remain off the coast
thru 12Z. Added areas of fog as well.

PVS DSCN:
The moisture flow out of the tropics continues this evening on
the eastern side of the broad upper trough. The forcing has lifted
to the NW with showers still linger across the north central
Piedmont and areas north of Richmond. Guidance suggest that this
area of lift will slowly lift off to the North. So have gradually
allowed the pops to decrease over western section overnight.
However...the lingering showers are not producing enough qpf to
warrant retaining the flash flood watch so have cancelled the
flash flood watch. But the ground does remain saturated so some
water problems will continue. In the east however...did follow the
trend of the models to pull the pcpn that is off the Carolina
coast back into the Delmarva toward morning. So have increase pops
their after 6z. For lows overnight did make some tweaks lower
based on current temps otherwise the remainder of the forecast is
unchanged.

Prev 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.

&&

.SHORT TERM /8 AM THIS 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 /06Z SATURDAY THROUGH WEDNESDAY/...
IFR ST and with variable VSBYS between 2-6SM were noted across
inland areas as well as the ern shore early this morning with sct
shwrs mainly along and west of the I95 corridor and the MD ern
shore. Kept VCSH along with a few hour Tempo group at RIC/SBY
based on crnt radar trends. Rain over the ocean appears to stay
east of SBY as it moves northward along the Mid Atlantic seaboard.
VFR CIGS were noted across ORF/ECG with MVFR CIGS at PHF where
drier air is beginning to surge northward. Expect VFR CIGS after
sunrise with VFR conditions all areas by 18Z as the drier air
continues to move north.

OUTLOOK...VFR conditions expected into early next week except for
lower VSBYS in early morning fog given the wet ground and longer
nites.

&&

.MARINE...
Forecast updated to extend the SCA over southern marine zones
through the early morning hours as buoy 44056, not too far
offshore, is still at 5 ft.

Previous discussion...
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...
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.

&&

.TIDES/COASTAL FLOODING...
* Updated at 1200 AM EDT. See numbered bullets below for
  additional details.

Strong/anomalous sfc high pressure remains over sern Canada
before weakening this aftn as stacked low pressure over the
Midwest drifts north and slightly east during this same timeframe.
This will translate into onshore/se winds transitioning to more
southerly (and decreasing) later today. 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 continues through 400 AM this 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 this aftn.

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

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

* Surf zone forecast has ended for the season.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory until 11 AM EDT this morning for MDZ024-
     025.
     Coastal Flood Warning until 4 AM EDT early this morning for
     MDZ021>023.
NC...None.
VA...Coastal Flood Advisory until 3 PM EDT this afternoon for
     VAZ089-090-093.
     Coastal Flood Advisory until noon EDT today for VAZ084>086-
     095>097-523>525.
     Coastal Flood Advisory until 11 AM EDT this morning for VAZ099-
     100.
     Coastal Flood Advisory until 4 PM EDT this afternoon for
     VAZ075>078.
MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ650-
     652-654.
     Small Craft Advisory until 7 AM EDT this morning for ANZ656-
     658.

&&

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