-- Discussion containing changed information from previous version are highlighted. --
389
FXUS61 KAKQ 242001
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
401 PM EDT Tue Sep 24 2024

.SYNOPSIS...
A series of shortwave troughs will slide across the region in
northwest flow aloft bringing unsettled conditions through
midweek. The remnants of Helene likely pass well west of the
area on Friday. Temperatures will gradually moderate through
midweek.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 350 PM EDT Tuesday...

Key Messages:

- Scattered showers and widespread clouds through this evening.

- Additional rain (and isolated thunderstorms) overspreads the
region this evening and continues through tonight.

- A Flood Watch is in effect for our southwestern counties later
this evening through tonight.

This afternoon, strong ~1024mb high pressure is centered over
northeastern Canada, wedging down into the local area. Meanwhile,
weak low pressure is located near the Great Lakes. A stationary
boundary is draped south and west of our local area. As low pressure
begins to lift further to the northeast overnight, the boundary will
slowly try to lift north into the region as a warm front.

Widespread clouds and scattered rain showers and drizzle/mist
remains across the area this afternoon. The current round of light
to moderate showers should continue to push off to the northeast and
gradually diminish over the next few hours, with a small amount of
drying late this afternoon into the early evening. Clouds, rain, and
an onshore wind have kept temperatures cool this afternoon, with
readings generally in the mid-upper 60s to lower 70s. A second wave
of showers (and isolated thunderstorms) is expected to develop and
move through the western half of the area later this evening through
tonight. This second round could produce locally heavy rainfall,
with many of the CAMs hinting showing higher QPF amounts across our
far southwestern counties. As a result, WPC has highlighted these
locations with a slight risk for excessive rainfall for tonight.
After collaborating with neighboring offices, a Flood Watch has been
issued for Prince Edward, Nottoway, Brunswick, Lunenburg, and
Mecklenburg. Scattered instances of flash flooding are possible,
especially in any poor drainage areas. There is a marginal risk for
excessive rainfall for much of the remainder of the area roughly
around I-95 and west. Low temperatures tonight will generally be in
the mid to upper 60s.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
As of 350 PM EDT Tuesday...

Key Messages:

- Continued cloudy conditions with additional chances for showers or
thunderstorms on Wednesday, especially west of I-95.

- The remnants of Helene move north Thursday night through Friday,
bringing additional rain chances to the area.

A warm front lifts north through the area tomorrow, bringing warmer
and more humid air back into the region. Additional shower and
storms will be possible Wednesday afternoon, especially along and
west of I-95. Heavy rainfall and potentially gusty winds will be
possible with any storms that develop. High temperatures tomorrow
will range from the mid-upper 70s north to the lower 80s south.
Drier on Thursday, with only low-end PoP chances (mainly west), but
still remaining fairly cloudy. Highs will range from the upper 70s
to lower 80s. Rain chances increase again Thursday night into Friday
as Helene moves north (remaining well west of the forecast area).
The best rain chances will likely be late in the day and Friday
night, with locally rainfall again a possibility (especially west).
Highs on Friday range from the mid 70s NW to lower 80s SE.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 350 PM EDT Tuesday...

Key Messages:

- Multiple low-end chances of rain late this week into the
  weekend from Tropical Storm Helene

- Drier and cooler air coming mid next week

There is some uncertainty about impacts from newly-named Tropical
Storm Helene for the weekend. The 12z ECMWF and GFS suggest remnants
split from Helene`s original track up GA to the W near the TN/MO
border and E over the ocean late Friday. The splitting of the low
pressure system could allow chc showers from residual energy and
moisture on Saturday, Sunday, and Monday. Temperatures Saturday and
Sunday will have highs in the 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 /20Z TUESDAY THROUGH SUNDAY/...
As of 200 PM EDT Tuesday...

MVFR CIGs continue with slight showers across the area and into this
evening. Some local IFR is possible. Continued rain chances
overnight around the major airports. MVFR CIGs will remain.
Winds will be ESE around 5-10 kt.

Chc of showers remain Wed (esply inland/RIC). MVFR and locally IFR
CIGs are possible. Thur is drier, but chc of showers returns on Fri
and Sat.

&&

.MARINE...
-- Changed Discussion --
As of 400 PM EDT Tuesday...

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 Thursday.

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

A warm front is located SW of the waters this afternoon, with low
pressure well offshore and high pressure ridging into the area from
New England. Tropical Storm Helene is situated over the NW Caribbean
Sea and is expected to track northward into the Gulf Mexico tonight,
per the latest NHC forecast. Locally, a relaxed pressure gradient is
leading to light-moderate winds as of 3 PM/19z, generally E ~10
kt. Seas remain elevated in the 4.5-7 ft range, highest N.
Small craft advisories remain in effect for all coastal water
zones and have been extended through most of Thursday as
confidence is high in these elevated seas continuing.

The eastern fringes of a LLJ overspreads the Chesapeake Bay tonight
and winds likely increase to 10-15 kt for a time after sunset. There
could be a few gusts to 20-25 kt in this timeframe, especially
across the northern bay. The duration and marginal wind speeds
precludes a small craft advisory at this time. Into Wednesday,
the high over New England retreats into the Canadian Maritimes
as TS or Hurricane Helene gets pulled northward through the
central and eastern Gulf. This will turn the flow to the SE or
SSE through at least Thursday, though wind speeds should average
10 kt or so. Helene makes landfall in the FL Big Bend region
Thursday, tracking inland along the southern Appalachians
Friday. The remnant low will probably lead to an increase in SE
winds by Friday afternoon and winds could approach low-end SCA
criteria of 15-20 kt with gusts to 25 kt. This appears most
likely over the southern coastal waters and lower Chesapeake
Bay, with lower chances further N. There is higher uncertainty
into Saturday as a cold front potentially pushes into the area
from the N or NW. The timing is overall slower with the 12z
guidance, delaying any increase in winds to Saturday night or
early Sunday. SCA conditions are possible behind this front as
NE winds make a return.

Seas remain 4-6 ft through most of this week and into the weekend
and SCAs will likely be needed for most of this period. Waves in the
Chesapeake Bay will average 1-2 ft through the weekend, except ~3 ft
at the mouth of the bay. Per the latest 12z NWPS output, 3-4 ft
waves are possible at the mouth of the bay tonight w/ the brief
increase in SE winds. Not enough confidence at this time to issue a
SCA, however. Depending on the frontal timing Sat-Sun, waves in the
bay could increase to 3-4 ft at times.

A high rip current risk is forecast through at least Wednesday.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
-- Changed Discussion --
As of 400 PM EDT Tuesday...

Key Messages:

- Long duration coastal flood event continues across the region (see
section below for info on this being a record at a few sites).

- Water levels are forecast to gradually subside over the next few
days.

- Coastal Flood Warnings remain in effect from Windmill
Pointt/Tappahannock northeastward to the bay side of the MD Eastern
Shore, with advisories elsewhere (see CWFAKQ for more details).

- Minor flooding likely persists into Wednesday across the middle
and upper bay.

Tidal departures are averaging 1.5-2 ft above astro tides this
afternoon. Only changes to the ongoing headlines was to refine the
timing with the ongoing or approaching afternoon/evening high tide.
High-end minor or low-end moderate tidal flooding is forecast in the
upper bay and along the Potomac/Rappahannock, including on the bay
side of the MD Eastern Shore, with this upcoming high tide cycle.
Accordingly, Coastal Flood Warnings remain in effect through this
evening (early Wed morning on the MD Eastern Shore).

Elsewhere, Coastal Flood Advisories are in effect across the lower
bay and York and James Rivers through this evening. Here, confidence
is low in exceeding minor flood and current tidal departures argue
water levels should peak within or below minor thersholds. Elsewhere
in the advisory area, only minor flooding is expected today. Also,
included MD Beaches in the ongoing advisory through 6 PM as Ocean
City crested just above minor flood w/ this afternoon`s high tide.

Water levels should gradually fall this week with decreasing
astronomical tides, but minor flooding is expected through much of
the week in areas near/adjacent to the mid/upper bay. Over the lower
bay, only nuisance/action-level at worst is expected.

As of 400 PM EDT Tuesday:

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

- Lewisetta (P.O.R. since 1979): 16 (with several more to come),
previous record was 8 in Oct 2021, Oct 2019, Oct 2015.

- Cambridge (P.O.R. since 1980): 10 (with several 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 may tie the record at Lewisetta).

- Lewisetta (P.O.R. since 1979): 6 (so far) ***record is 7 in Oct
2015***

- Cambridge (P.O.R. since 1980): 1 (so far and unlikely to occur  on
consecutive tide cycles)  ***record is 4 in Oct 2019***
-- End Changed Discussion --

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Warning until 2 AM EDT Wednesday for MDZ021>023.
     Coastal Flood Advisory until 6 PM EDT this evening for MDZ025.
NC...None.
VA...Coastal Flood Advisory until 6 PM EDT this evening for VAZ084-
     086-523>525.
     Flood Watch from 8 PM EDT this evening through Wednesday
     morning for VAZ060-065>067-079.
     Coastal Flood Warning until midnight EDT tonight for VAZ075-
     077.
     Coastal Flood Warning until 10 PM EDT this evening for VAZ076-
     078-085-521-522.
     Coastal Flood Advisory until 8 PM EDT this evening for VAZ083-
     095>100-518-520.
     Coastal Flood Advisory until 10 PM EDT this evening for VAZ089-
     090-093.
MARINE...Small Craft Advisory until 7 PM EDT Thursday for ANZ650-652-
     654-656-658.

&&

$$

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