641
FXUS61 KAKQ 270732
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
332 AM EDT Fri Sep 27 2024

.SYNOPSIS...
Hurricane Helene is lifting quickly northward across Georgia
this morning. The remnants of Helene will then pass well west
of the area this afternoon and evening. Drier conditions
briefly return on Saturday, followed by unsettled weather Sunday
into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM EDT Friday...

Key Message:

- Widespread showers and isolated thunderstorms are expected
  this afternoon into this evening, as Helene`s circulation
  lifts north into Georgia. Locally heavy rain and brief
  tornadoes are the main threats.

Helene made landfall as a category 4 hurricane last night along the
Big Bend of Florida. Since landfall, Helene has quickly moved north
into central Georgia and is forecast to be near the Atlanta metro by
8am EDT this morning and into southern Kentucky by this evening.
Radar shows some light echoes across the SW third of the area early
this morning. Expect the bulk of the rainfall today will come with a
quasi warm-frontal feature lifting northward through the Carolinas
and into Virginia by early afternoon. Latest hi-res guidance shows
sharply increasing PoPs with this feature as very deep moisture
(PWATs 2-2.25") lifting into the local area as flow at the surface
and aloft strengthens considerably as Helene makes its closest
approach. Widespread cloud cover will limit surface heating but
strong theta-e advection will allow at least a few hundred J/Kg of
SBCAPE across the area this afternoon. This instability combined
with increasing shear will result in favorable conditions for
isolated tornadoes this afternoon. SPC has expanded the Slight Risk
area a bit northward on the latest update which is now generally
along and south of the US 460 corridor but also includes the Newport
News/Norfolk metro areas. A Marginal Risk includes the remainder of
the area except portions of the MD Eastern Shore which will be the
farthest removed from Helene`s influence. The heaviest rainfall will
generally be west of the local area but any storms this afternoon
will have the potential to put down a lot of precip in a short
period of time. WPC has the entire area in a Marginal Risk for
excessive rainfall with the potential for areas of flash flooding,
especially in urban and poor drainage areas. The showers and storms
will lift northward this afternoon with a mid level dry slot
following close behind, shutting off the heavy precip potential
rather quickly from south to north. Additional showers are likely
across northern half of the area into the evening but the bulk of
the heavy rain and tornado threat will come this afternoon. Average
storm total rainfall will be on the lower side with around 1 inch
likely for the Piedmont, tapering to ~0.5-0.75" for the Tri Cities
SE into northeast NC. The remainder of the area will likely see 0.5"
or less but very heavy rain rates could easily drop a quick inch or
two of precip in localized areas.

Needless to say, it will be quite warm and muggy today with deep
tropical moisture moving into the area. High temps today top out in
the mid to upper 70s for inland locations and around 80 degrees near
the coast. Breezy conditions will spread northward late this morning
into the afternoon with gusts generally in the 25-30mph range. The
strongest winds will be favored over the southwest half of the area,
closer to Helene`s circulation but some strong gusts are like near
the coast as well. Low temps tonight range from the mid 60s in the
Piedmont to the low 70s elsewhere.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
As of 355 PM EDT Thursday...

Key Messages:

- Mainly rain-free and warm/humid Saturday.

- Cloudier and slightly cooler Sunday, with chances for a few
showers returning.

On Saturday, the remnants of (weakening) Helene will be located well
off to our west over western KY and the remnant sfc circulation will
slowly fill in underneath the upper low. Drier weather returns
outside of some low- end rain chances across the NW late. High temps
warm into the low-mid 80s under a mostly sunny sky. Lows Sat night
in the mid 60s.

Conditions turn more unsettled more Sunday as the upper low/trough
over the OH Valley translates eastward. Therefore, expecting more in
the way of cloudiness and chances for showers (especially NW). Some
uncertainty surrounds rainfall coverage, with the 12z GFS showing
more precip than the ECMWF. The GFS solution would lead to cooler
high temps vs. the ECMWF. For now, will go with NBM highs, which is
a few degrees cooler than Saturday and in the upper 70s-low 80s (mid
80s possible far SE). Lows Sun night in the 60s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 330 PM EDT Thursday...

Key Messages:

- Multiple low-end chances of rain Sunday through Tuesday early from
  the post tropical remnant of Hurricane Helene.

- Drier and cooler air arrives mid to late next week.

The latest model guidance indicates the remnant low of Hurricane
Helene will gradually shift to the east through Tue after stalling
near the TN valley on Sunday. This will keep conditions unsettled,
with chcs for showers and a few tstms. High temperatures Mon-Wed
will be in the mid-to-upper 70s with lows in the low 60s Mon-Tue
night. A dry cold front is expected around Tuesday night. There is
some model differences on the timing, but cooler overnight lows in
the low-to-mid 50s across the piedmont and inland and upper 50s near
the coast for Wed-Thur night are possible. After the cold front,
significantly lower humidities are expected.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
As of 825 PM EDT Thursday...

Just isolated to sctd showers were lifting nwrd across our extrm
wrn counties this evening. SBY already had IFR CIG. Any VFR CIGs
late this evening will gradually become MVFR or IFR (locally
LIFR) at all TAF sites late tonight through late Fri morning,
in advance of bands of showers associated with tropical cyclone
Helene. MVFR/IFR conditions then expected at all TAF sites from
Fri aftn into Fri evening, as bands of showers, possible tstms
move through the area. Higher winds will be possible in any
stronger showers or storms. After sunrise, ESE winds will pick
up and gust to at least 20-25 kt in the aftn into the evening.

Outlook: Fri night and Sat will be drier with mainly VFR
conditions. A chc of showers is possible with unsettled wx Sun-
Mon.

&&

.MARINE...
As of 330 AM EDT Friday...

- Small Craft Advisories remain in effect across all waters through
part of tonight for southeast winds. Occasional gusts to 35 knots
are possible across the southern waters late this afternoon through
this evening.

- Sub-advisory conditions are expected from late Saturday through
Monday.

- Another round of SCAs is possible Tuesday through Wednesday.

E to SE winds near 10 kt prevail across the waters early this
morning as Hurricane Helene is tracking north across Georgia. Helene
will continue to move quickly north through Georgia before
transitioning into an extratropical cyclone over eastern Tennessee
by this evening/tonight. Even though Helene will remain well to our
WSW, the pressure gradient will tighten later today over the waters,
allowing SE winds to increase to 15-25 kt this aftn/evening with
frequent gusts of 25-30 kt. SCAs remain in effect for all waters
through 1 AM (and have been extended until 7 AM Sat for the ocean).
The gradient relaxes early Saturday morning, allowing winds to veer
to the SSW and diminish to ~10 kt by sunrise as the remnant
circulation from Helene gets shunted NW on the northern periphery of
an upper level low over Tennessee.

Will also have to watch for convection over the waters from this
aftn-late evening, which could necessitate SMWs for 34 kt+ gusts. In
addition, can`t rule out occasional gusts of 35 kt outside of any
storms between 4-10 PM. However, these won`t be frequent enough to
warrant gale headlines. Local wind probs for gale gusts have
increased...but are no higher than 10% over the waters for a few
hours this evening. Seas build to 4-7 ft while waves on the bay
build to 3-5 ft before slowly subsiding later tonight. Sub-SCA south
winds are expected on Sat, with winds becoming E at ~10 kt on Sun.
However, seas may remain around 5 ft through much of Saturday before
subsiding to 3-4 ft by Sat night.

A secondary low may develop along or just off the coast on
Tuesday/Wednesday, which could bring another round of SCAs (with
northerly winds) to the waters. The high rip current risk continues
for all beaches today (and for the northern beaches on Sat).

&&

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

Key Messages:

- Tidal departures will increase later today through part of
  tonight (mainly on the west side of the bay and across the
  upper bay) due to an increase in southeasterly winds.

- Coastal Flood Warnings have been issued from Lewisetta to
  Tappahannock for this evening`s high tide, with moderate tidal
  flooding expected. Advisories are in effect for the bay side
  of the MD Eastern Shore with Advisories/Statements for other
  areas on the west side of the bay south to the James River.

- Back Bay of VA Beach (in addition to areas along the north
  side of the Albemarle Sound) will likely see nuisance/minor
  flooding later today-tonight.

Tidal departures continue to fall early this morning (and are
between 1.0-1.5 feet above normal), but will rise later today
through part of tonight with the expected increase in SE winds. With
the wind guidance a bit higher than it was 12-24 hrs ago, ETSS has
come up a few tenths of a foot across the Rappahannock/tidal
Potomac. Also, a decent flood tide is expected at the mouth of the
bay this evening (coinciding with the peak in the SE winds). Given
these factors, have gone ahead and issued Coastal Flood Warnings for
the tidal Potomac and upper Rappahannock for this evening`s high
tide (which includes Lewisetta/Tappahannock). Windmill Pt has been
tracking a couple tenths of a foot below these two locations over
the past few tide cycles (and ETSS is forecasting minor flooding),
so went with an advisory from Lancaster County south to Mathews
County. Statements are in effect for areas along the York/James
Rivers where nuisance flooding is expected. Will keep the advisories
for the upper bay through tonight`s high tide cycle. While Bishop`s
head is forecast to exceed moderate flood stage, other sites should
only see minor flooding.

Lastly, will continue to watch areas adjacent to the
Currituck/Albemarle Sounds (including Back Bay of VA Beach)
today/tonight as SE winds could push already elevated water levels
up further into minor flooding thresholds. For now, have gone with a
Coastal Flood Statement for these areas but future shifts may need
to upgrade to an advisory if trends warrant.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory until 8 AM EDT Saturday for MDZ021>023.
NC...None.
VA...Coastal Flood Advisory until 6 PM EDT this evening for
     VAZ075>077-521-522.
     Coastal Flood Warning from 6 PM this evening to 4 AM EDT
     Saturday for VAZ075>077-521-522.
     Coastal Flood Advisory until 2 AM EDT Saturday for VAZ078-085-
     086.
MARINE...Small Craft Advisory from 7 AM this morning to 1 AM EDT
     Saturday for ANZ630>632-634>638.
     Small Craft Advisory from 7 AM this morning to 10 PM EDT this
     evening for ANZ633.
     Small Craft Advisory until 7 AM EDT Saturday for ANZ650-652-
     654-656-658.

&&

$$

SYNOPSIS...RHR
NEAR TERM...RHR
SHORT TERM...RHR/SW
LONG TERM...RHR
AVIATION...RHR
MARINE...ERI
TIDES/COASTAL FLOODING...