-- Discussion containing changed information from previous version are highlighted. --
497
FXUS61 KAKQ 191902
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
302 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/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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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.
-- End Changed Discussion --

&&

.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 330 AM EDT Thursday...

Key Messages:

- Small Craft Advisories continue for coastal waters off the Eastern
Shore into this afternoon

-Additional Small Craft Advisories likely this weekend into early
next week

Onshore/NE flow continues this morning as low pressure remains
situated off the Mid-Atlantic coast. Winds are breezy at 10-15kt
with gusts to 20kt as of latest obs. Buoy obs reflect seas around
4ft S of Cape Charles Light and 5-6ft to the N. SCAs are still in
effect for the elevated seas. May need to extend the SCA for the
waters between Cape Charles and Parramore Island past the set 4am
expiration time given the latest obs. Low pressure will slowly nudge
further NE today and high pressure centered to the N will fill in
over the local area behind it. The relaxing pressure gradient will
allow for further improvement in marine conditions. Winds shift to
the N by the afternoon and 9-13kt,then further diminish to the 5-
10kt later tonight. Expect seas to gradually improve as well,
especially once winds become less onshore. Seas should be down to
~4ft across the coastal waters by late this evening.

Low pressure to the NE will more or less remain in place on Fri.
While N/NE winds will be sub-SCA at 10-15kt Fri-Sat, swell from the
offshore low arrives Fri morning, leading to increasing seas once
again. Northern coastal waters will see 5-6ft seas by Fri afternoon.
Southern coastal waters likely start to see the 5ft seas late Fri
night/early Sat morning. The pressure gradient over the waters will
start to tighten up again Sun as the low shifts SE. This will lead
to increased NE winds Sun, especially over coastal waters. The
bay/rivers will likely need SCAs for winds ~20kt. Winds over coastal
waters look to be 20-25kt. Swell combined with elevated winds will
allow seas to build to 6-8ft in the N and 5-7ft S. While winds look
to improve early next week, seas will be slow to drop off once
again.

&&

.TIDES/COASTAL FLOODING...
As of 330 AM EDT Thursday...

Astronomical tides will continue to increase with the approach of
the next full moon. Higher astro tides along with prolonged onshore
flow will continue to produce 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
expected for the next high tide cycle as well.

Additional advisories/extension of Advisories will likely be needed
through the end of the week and into the weekend due to extended
periods of onshore flow and high astro tides. Building flood tide
Saturday into Saturday night does bring the potential for tide
levels reaching moderate Coastal Flood Thresholds (best chances
northern coastal zones and lower bay) for tide cycles over the
upcoming weekend. Coastal Flood Watches may be issued in upcoming
forecast cycles.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

$$

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