543
FXUS61 KAKQ 260005
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
805 PM EDT Wed Sep 25 2024

.SYNOPSIS...
A weak boundary lingers near the region tonight through
Thursday. Hurricane Helene intensifies tonight, before making
landfall on the Florida Gulf Coast Thursday evening. The
remnants of Helene will then pass well west of the area on
Friday. Drier conditions briefly return on Saturday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 330 PM EDT Wednesday...

Key Message:

- Scattered showers and thunderstorms are possible this afternoon
into tonight.

This afternoon, a slow moving warm front is bisecting the region
(roughly located along or just south of I-64). South of the front,
skies have become partly sunny and temperatures have climbed into
the lower 80s. North of the front, still seeing plenty of cloud
cover and temperatures only in the lower 70s. In addition, south of
the front SBCAPE has increased to ~1500 to 2000 J/kg along with 30-
40 knots of bulk shear, thus we may see a few showers/thunderstorms
develop over the next couple of hours. Showers and thunderstorms
should be scattered in nature, with generally 30-40% PoPs in the
forecast. Tonight, low clouds increase once again as well as the
potential for some patchy fog (best chances over the Piedmont). Low-
end rain chances may linger across western portions of the area
through much of the night. Low temperatures fall back into the mid
to upper 60s tonight.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
As of 330 PM EDT Wednesday...

Key Messages:

- Slightly drier conditions for Thursday

- The remnants of Helene move well west of the area on Friday,
bringing the potential for moderate to locally heavy rain and an
isolated tornado threat.

- Drier weather returns for Saturday.

By tomorrow morning, Hurricane Helene will likely be intensifying
into a major hurricane over the Gulf of Mexico as it moves north.
The storm is then expected to make landfall late Thursday
afternoon/evening along the Florida Gulf Coast. Tomorrow will be
another cloudy day, with the boundary from today still lingering
near the area. The chance for scattered showers or storms gradually
expands from the west throughout the day with ~30% PoPs west of I-95
to 20% or less further east. Rain chances begin to pick up area-wide
Friday night into early Saturday as the TC Helene lift north through
western GA. The best rain chance for us occurs Friday morning
through Friday afternoon, before a dry slot moves in from the south
Friday evening into Friday night. By Saturday morning, the remnants
of Helene will be located well off to our west over western KY.
Drier weather returns outside of some low-end rain chances across
the NW.

Rainfall wise, expecting around ~1.00" to 1.50" across the western
half of the area with some locally higher amounts. East of I-95, we
will generally see 0.50" to 1.00". Max wind gusts with the system
will generally be on the order of 20 to 25 mph. We will be watching
the potential for an isolated tornado threat on Friday, with SPC
expanding the Day 3 Marginal Risk to include much of the southern
half of the forecast area. Any deeper convective cores that are able
to develop may have the potential to produce damaging wind gusts and
potentially a tornado due to the strong low/mid level flow ahead of
the remnants of Helene.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 330 PM EDT Wednesday...

Key Message:

- Multiple low-end chances of rain Saturday night into early
  next week from Hurricane Helene

- Drier and cooler air coming mid next week

Latest ensemble guidance indicated that Hurricane Helene will move
across portions of the SE and stall over the central Ohio River
Valley by Saturday. The remnants of Helene`s energy and moisture
bring a chc of showers for Saturday night into early next week.
Temperatures Sunday and Monday will have highs in the mid- to-
upper 70s and lows in the low-to-mid 60s. The last of the
moisture will be squeezed out on Tuesday by a frontal passage
which will bring drier and cooler conditions Tuesday and
Wednesday with highs in the mid 70s and lows around 60F.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 805 PM EDT Wednesday...

Isolated showers were occurring over srn portions of the region
this evening. Otherwise, expect MVFR and locally IFR flight
restrictions overnight through Thu morning. Mainly VFR CIGs
expected for Thu aftn into Thu evening at all TAF sites except
maybe SBY.

Outlook: The exact impacts of Hurricane Helene has some uncertainty,
but heavy rain and perhaps gusty winds are possible Fri. As the
moisture and chc of rain continues Fri and Sat, it`s possible
to have late night/early morning sub-VFR ceilings and visibilities.

&&

.MARINE...
As of 330 PM EDT Wednesday...

Key Messages:

- Elevated seas persist through most of this week and into the
coming weekend. Small craft advisories have been extended on the
coastal waters through Friday.

- The remnants of Tropical Cyclone Helene pass well inland Friday,
with impacts locally limited to gusty SE winds Friday-Friday night.

High pressure remains centered over Atlantic Canada this afternoon,
ridging southward into the Mid-Atlantic and Carolinas. Locally, the
flow is gradually becoming SE and wind speeds are generally around
10 kt. Waves in the Chesapeake Bay are 1-3 ft (highest at the mouth)
and seas offshore remain in the 4-6 ft range. Hurricane Helene has
emerged into the Gulf of Mexico as of 2 PM/18z and will continue N
or NNE through today and tonight.

Hurricane Helene will approach the FL Gulf coastline on Thursday,
making landfall in the Big Bend region Thursday evening (per the
latest NHC forecast). Ahead of this feature, the sfc high to our NE
will be shunted further offshore, with one lobe remaining over
Atlantic Canada and another piece breaking off near Bermuda. This
evolution will allow for a tightening pressure gradient over the
area Friday and SE winds are forecast to increase to 15-20 kt with
gusts to ~25 kt. Wind probabilities for 18 kt sustained and 25 kt
gusts are highest over the southern coastal waters and the central
and southern Chesapeake Bay. However, SCAs are possible for all
waters and they will be in effect regardless for all coastal waters
due to a continuation of the >5 ft seas. Winds relax considerably
for Saturday, but remain out of the E or SE. Confidence is lower by
Sunday into early next week as backdoor cold front potentially
approaches from the N, which could lead to a period of elevated
winds across the northern waters. Some guidance also develops a weak
non-tropical low in our vicinity offshore. Either way, there will
likely be a period of small craft advisory conditions at some point
early-mid week.

Seas of 4-5 ft are expected through most of this week and the
weekend. Small craft advisories have been extended through Friday
for the coastal water zones (further extensions are also likely).
Waves in the bay will average 1-2 ft, with 3 ft at the mouth of the
bay. As SE winds increase Friday, there could be a period of 6 ft
seas and 4 ft waves at the mouth of the bay.

A high rip current risk continues through the end of week given 3-5
ft nearshore waves and 10-12 sec periods.

&&

.TIDES/COASTAL FLOODING...
As of 330 PM EDT Wednesday...

Key Messages:

- Tidal departures falling across the region.

- Coastal flood advisories in effect for the tidal Potomac and
Rappahannock for the Wednesday evening high tide cycle.

Tidal departures continue to fall this afternoon, but remain highest
(around 2 ft) in the upper Chesapeake Bay, along the tidal Potomac
and Rappahannock, and on the bay side of the MD Eastern Shore.
Coastal flood advisories remain in effect through late this evening
or early Thursday for the upcoming high tide cycle in these areas.
Low-end moderate flooding cannot be ruled out at Bishops Head, but
will refrain from any warnings as Crisfield and Cambridge are
forecast to remain within minor flood thresholds. Only nuisance-
level flooding is expected with the following high tide around
sunrise, with the exception of Lewisetta and Bishops Head, who both
could touch minor flood. Will let the next shift decide if
advisories are needed for this cycle. Otherwise, water levels fall
further to end the week and any nuisance-minor flooding will likely
be constrained to tidal Potomac and bay side of the MD Eastern
Shore.

Lastly, will need to watch areas adjacent to the Currituck Sound
(including Back Bay) and the Albemarle Sound Friday as SE winds
could push already elevated water levels up further into minor
flooding thresholds.

As of 300 PM EDT Wednesday:

Consecutive high tides reaching at least Minor Flood with this event:

- Lewisetta (P.O.R. since 1979): 17 (with possibly one more to
come), previous record was 8 in Oct 2021, Oct 2019, Oct 2015.

- Cambridge (P.O.R. since 1980): 12 (with possibly one more to
come), previous record was 5 in Oct 2021, Oct 2019, Sep 2018, Oct
2011.

Consecutive high tides reaching at least Moderate Flood with this
event: (this event tied the record at Lewisetta).

- Lewisetta (P.O.R. since 1979): 7  ***record was 7 in Oct 2015***

- Cambridge (P.O.R. since 1980): 1  ***record is 4 in Oct 2019***

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory until 2 AM EDT Thursday for MDZ021>023.
NC...None.
VA...Coastal Flood Advisory until midnight EDT tonight for
     VAZ075>078-085-521-522.
     Coastal Flood Advisory until 10 PM EDT this evening for VAZ099-
     100.
MARINE...Small Craft Advisory until 7 PM EDT Friday for ANZ650-652-654-
     656-658.

&&

$$

SYNOPSIS...AJB
NEAR TERM...AJB
SHORT TERM...AJB
LONG TERM...HET/KMC
AVIATION...KMC/TMG
MARINE...SW
TIDES/COASTAL FLOODING...AKQ