447
FXUS61 KAKQ 191919
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
319 PM EDT Thu Sep 19 2024

.SYNOPSIS...
High pressure will remain north of the region while low pressure
remains well offshore. A backdoor cold front potentially drops
back south across the region Saturday. High pressure builds north
of the area this weekend into early next week leading to generally
dry conditions. A cold front potentially approaches by the middle
to later portions of next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 300 PM EDT Thursday...

Key Messages:

- Trending drier with low-end shower chances for inland areas SW of
I-64.

- Patchy fog possible tonight.

Afternoon analysis shows sprawling low pressure offshore of the
area, with several areas of low-level vorticity noted on the latest
visible satellite images. A trough over the eastern CONUS aloft
will act to slowly deepen this low as it gradually drifts S
over the next few days. Elsewhere, a weak stationary front is
located S of the area, with a remnant upper low spinning over
the eastern half of the area. NNE winds from these sfc features
are gradually scouring out the thicker cloud cover this
afternoon and skies range from sunny/mostly sunny up on the
Eastern Shore to partly-mostly cloudy over the Piedmont and in
NE NC. Temps have warmed into the upper 70s or lower 80s for
areas that have seen appreciable clearing, while mid 70s persist
for those areas still seeing the clouds and/or showers.
Speaking of showers, there are isolated showers in our western
tier of counties associated w/ a weak area of convergence and
the upper low. Coverage should remain on the low side and the
thinking is that 30% PoPs covers this activity well. Elsewhere,
could see additional isolated activity develop across the S/SW
and in NE NC near the Albemarle Sound. General trend has been
for drier wx so have cut back on PoPs here compared to earlier
forecasts. Little to no thunder is expected given MLCAPE ~500
J/kg. Skies become mostly clear tonight before patchy fog and/or
stratus develops. Not expecting widespread dense fog at this
time, but could see some patches of 0.25-1.0 mile visibilities.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
As of 300 PM EDT Thursday...

Key Messages:

- Drier weather returns Friday into Saturday.

- Showers or isolated storms possible Saturday evening into Saturday
night.

- Cooler and mainly dry Sunday.

Fairly pleasant Friday and Saturday with high pressure over New
England extending down into the local area. Meanwhile, the
previously referenced coastal low will linger well off the Mid
Atlantic coast. Sunshine returns in earnest for Friday, with
temperatures generally in the lower 80s (70s along the immediate
coast). Low temperatures Friday night range from the upper 50s to
lower 60s. There is less fog potential Friday night given lower dew
points, but cannot rule it out (especially S). Mostly sunny skies
continue into Saturday, with highs again in the upper 70s to lower
80s. Clouds increase late in the day and especially overnight as a
shortwave on the wrn periphery of the upper trough drops
through the area and a backdoor cold front-type features moves
through at the sfc. These features could spark showers and
isolated storms NW of the area later Saturday, possibly moving S
into the area by the evening and overnight hours. While
moisture profiles are not overly impressive, most guidance
suggests something in the way of precip moving through and have
MUCAPE actually increases some overnight as the cooler air aloft
moves in, so there could be some rumbles of thunder with this
activity. Lows Sat night around 60 F.

Sunday will be cooler behind the front with afternoon highs in the
mid-upper 70s. Will maintain a dry forecast for now, but there could
be some lingering showers given the nearby upper trough.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 300 PM EDT Thursday...

Key Messages:

- Starting off cool Monday with dry conditions.

- Gradually warming temps expected by the midweek, with low-end
precipitation chances potentially returning.

Offshore low pressure and associated upper low will depart well to
our SE by early next week. This will bring rising mid/upper heights
to the area, with a SW-NE oriented ridge forecasted to develop over
the eastern CONUS. Thus, temperatures should gradually moderate back
into the lower 80s by Tuesday and Wednesday. Monday, however, will
be dry and feature slightly below normal highs in the mid 70s with
gusty NE winds (especially along the coast) and partly-mostly cloudy
skies. Precip chances potentially inch back up by Tuesday and
especially Wednesday as a quick-moving shortwave ejects out of the
Midwest, likely interacting with the next deep-layer trough coming
out of the nrn US and Canada. 12z deterministic guidance shows
several waves of precip associated with various smaller-scale
disturbances. Timing these disturbances is difficult at this lead
time and given associated spread across the ensemble guidance, will
remain near or slightly above NBM PoPs during this period. This
yields slight chc PoPs Tuesday aftn across the W, with 20-30% PoPs
for most of the area Wednesday-Wednesday night with the parent cold
front. Sky cover averages partly-mostly cloudy. Forecast overnight
lows are in the upper 50s-lower 60s Sunday night, mid-upper 50s
Monday night, and lower 60s Tuesday/Wednesday night.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
As of 145 PM EDT Thursday...

Conditions have been improving through the late morning and
early afternoon hours at the terminals as relatively drier air
filters into the area from the N. Generally seeing MVFR- VFR
CIGs, with the thickest cloud cover (BKN-OVC) across the
Piedmont and in NE NC. Seeing FEW-SCT cloud cover elsewhere,
including at SBY. Similar conditions through the rest of the
daylight hours today, with CIGs expected to lift a little more
(to 3-4k ft AGL) and skies averaging SCT-BKN. Additional IFR
(and possible LIFR) could develop tonight from low stratus
and/or fog. Guidance is not in the best agreement, thus
confidence is on the low side. However, the best chance for
dense fog appears to be at ECG, with patchy fog or stratus
elsewhere. Will not explicitly show IFR/LIFR in the TAF as of
now, but have introduced MVFR VSBY in the 07-13z timeframe.
Conditions improve after 13-14z Friday and mostly sunny skies
are expected by the early afternoon.

N-NNE winds average 5-10 kt this afternoon and become 5 kt or
less tonight. Similar winds expected Friday.

Outlook: Gradually improving and primarily VFR conditions are
expected Friday through the weekend and into early next week.

&&

.MARINE...
As of 320 PM EDT Thursday...

Key Messages:

- Small Craft Advisories have been lowered for now.

- Additional Small Craft Advisories possible as early as tomorrow
afternoon for seas, with SCA likely this weekend into early next
week.

- Stronger NE winds develop late Saturday and Sunday, with
persistent long period swells keeping seas elevated this weekend
into the middle of next week.

Latest obs and buoy reports reflecting N/NE winds 10-15 kt over the
waters this afternoon. Deepening ~1004 mb sfc low pressure continues
meander just south of the southern New England coast, with the
system stalled due to a blocking area of high pressure centered off
the coast of Nova Scotia. Meanwhile, weak 1015+mb sfc high pressure
builds NW of the waters. Resultant NNE winds continue this evening,
backing to the NW as the surface high starts to build overhead.
Buoy obs reflect seas subsiding largely as expected this afternoon.
Seas were 3-4ft S of Cape Charles Light and ~4-5ft to the N. SCAs
were lowered earlier today south of Parramore Island, and will be
allowed to expire with the issuance of the afternoon package.

Winds slowly diminish and back to the NW as the pressure gradient
relaxes with high pressure building across the lower mid-Atlantic.
will allow for further improvement in marine conditions. Expect seas
to gradually improve as well with winds turning offshore and
diminishing. Seas generally 3-4 ft, waves 1-2 ft.

Previously referenced blocked low pressure south of Nantucket
remains more or less in place on Fri. While N/NE winds will be sub-
SCA at 10-15kt Fri-Sat, E-NE wind waves (8-10 second swell)
from the offshore low arrives Fri morning into the afternoon,
leading to seas increasing once again. Northern coastal waters
will see 5-6ft seas by midday Friday, and by late Friday
evening into Sat morning across southern coastal waters and the
mouth of Chesapeake Bay. The pressure gradient over the waters
also starts to tighten up again late Saturday and Sunday as the
low dives SE. This should increase NE winds during this period,
especially over coastal waters. The bay/rivers will likely need
SCAs for winds ~20kt as early as late Sat night, but more
likely on Sunday. Winds over coastal waters look to be 20-25kt.
Building swell combined with elevated winds should allow seas to
build to 6-8ft in the N and 5- 7ft S. While winds look to
improve early next week, but energetic long period (E-NE, ~10
second) swells from the lingering low well offshore of New
England will keep seas in 4-6 ft range over the coastal waters
through at least the middle of next week.

&&

.TIDES/COASTAL FLOODING...
As of 320 PM EDT Thursday...

Astronomical tides continue to increase with the approach of the
coming full moon (Harvest moon) cycle. Astronomically higher astro
tides, along with prolonged onshore flow will continue to produce
tidal anomalies of 1-1.5 ft, resulting in nuisance to low-end minor
tidal flooding across much of the area along the bay and tidal
rivers through the end of the week. Have opted to extend the Coastal
Flood Advisories given similar water levels near minor flood
thresholds through Friday evening`s high tide cycle. While winds
briefly diminish and turn offshore, the ebb tide will be short-
lived, as winds turn back onshore over the weekend.

Additional extension of advisories or perhaps Coastal Flood Warnings
are likely to be needed over the weekend. Will hold coastal flood
headlines at Friday night for now. Winds turning back onshore and
gradually increasing Sat night and Sunday should bring building
flood tide Saturday into Saturday night. With anomalies
increasing once again, the potential for tide levels reaching
moderate Coastal Flood Thresholds (best chances northern coastal
zones and lower bay) does increase for tide cycles over the
upcoming weekend. Coastal Flood Watches may be issued in
upcoming forecast cycles for the weekend.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory until 6 AM EDT Saturday for MDZ021>023.
     Coastal Flood Advisory until 2 AM EDT Saturday for MDZ025.
NC...Coastal Flood Advisory until 2 AM EDT Saturday for NCZ102.
VA...Coastal Flood Advisory until 6 AM EDT Saturday for VAZ075-077.
     Coastal Flood Advisory until 2 AM EDT Saturday for VAZ078-
     084>086-095>100-523>525.
MARINE...Small Craft Advisory until 4 PM EDT this afternoon for ANZ650-
     652.

&&

$$

SYNOPSIS...AJB/SW
NEAR TERM...SW
SHORT TERM...AJB/SW
LONG TERM...SW
AVIATION...SW
MARINE...MAM
TIDES/COASTAL FLOODING...