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920
FXUS61 KAKQ 261513
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
1113 AM EDT Thu Sep 26 2024

.SYNOPSIS...
Hurricane Helene intensifies today, before making landfall on
the Florida Gulf Coast this evening. The remnants of Helene
will then pass well west of the area on Friday. Drier conditions
briefly return on Saturday, followed by unsettled weather Sunday
through next Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 1110 AM EDT Thursday...

Key Message:

- Isolated to scattered showers redevelop this aftn, mainly W
  of I-95, with only a slight chance to the east.

The latest wx analysis indicates Hurricane Helene moving N over
the eastern Gulf of Mexico (105 MPH Cat 2 as of the 11 AM
NHC advisory), with ~1028mb sfc high pressure anchored across
Atlantic Canada, bringing E-SE onshore low level flow. A potent
upper low is spinning across the lower OH/mid MS Valley,
bringing southerly flow aloft from the eastern Gulf of Mexico
north to the eastern CONUS. Mainly dry conditions are noted
across our entire forecast area and latest visible satellite
even shows some sun peaking through over SE VA and on the
Eastern Shore. Warm and rather muggy with temps already near 80
E of I-95, with mid 70s to the W.

Expect mostly dry conditions through this morning, with some
showers/isolated storms expected to redevelop in the aftn along
and W of I-95. Will have PoPs ~40% in the Piedmont (50% across
the far SW), tapered to only 15-20% to the east. Hurricane
Helene will be moving NNE towards northern FL during the aftn,
with a forecast landfall in the Big Bend region tonight per the
latest NHC track. Partly to mostly cloudy into this afternoon
and have increased highs a degree or two into the 80-82 F range
given the current trend in obs.

Into tonight, we should remain too far removed from Helene for
anything more than a low chc for showers and perhaps a few
embedded tstms (mainly W of I-95). Far SW portions of the local
area may see an increase in PoPs towards sunrise Fri, but
overall the main batch of precip will not arrive until the day
Friday. Warm and humid with lows in the upper 60s to lower 70s.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 405 AM EDT Thursday...

Key Messages:

- Helene weakens and tracks well west of the area Friday,
  bringing the potential for moderate to locally heavy rain and
  a tornado threat (mainly to southern VA and NE NC zones).

- Mainly rain-free and warm/humid Saturday.

Rain chances rapidly increase after daybreak Friday, with PoPs
rising to likely to categorical over the W/SW 1/2 of the area,
overspreading the entire CWA by late morning or early aftn. The
overall trends with respect to total QPF are similar or slightly
lower compared to the previous model cycle. The ensemble means
are less than 0.50" over the NE portion of of the CWA to ~1.00"
over the western piedmont, but as usual much higher local
amounts will be possible. Perhaps the greater concern will be
for a tornado threat sometime from later Fri morning through Fri
aftn as instability develops across NC and into at least
southern portions of VA. Ample low level shear will be in place
with strong SSW flow aloft and SE low level winds, yielding
large, curving hodographs. Farther north, the amount of
instability will be less so the threat is lower. Uncertainty in
the exact track of Helene makes the severe threat somewhat
uncertain, but there is enough consensus for SPC to have NE NC
into a Day Slight Risk (primarily for the 5% TOR threat), with a
marginal (2% TOR threat) into southern and central VA (roughly
to the I-64 corridor). A dry slot moves in from the south late
Fri aftn/Friday evening into Friday night, bringing an end to
the precip. On Saturday, the remnants of (weakening) 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
late.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 415 AM EDT Thursday...

Key Message:

- 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

Latest ensemble guidance indicates that the remnant low of
Hurricane Helene will stall and slowly weaken across the lower
OH or upper TN Valley Sunday, with the upper low gradually
shifting to the east through Tuesday. Overall, this will keep
conditions unsettled, with daily chances for showers and a few
thunderstorms. Temperatures Sunday will remain warm with highs
into the upper 70s to lower 80s, then trending cooler Mon-Tue as
the upper low will be more centered near the region, bringing
highs in the 70s. Lows will generally be in the 60s. Model
differences remain as to how fast the upper low and the
associated cold front pass by the region towards the end of the
period with the GFS/GEFS being the most progressive while the
ECMWF/ENS and Canadian/GEPS are weaker with the initial upper
low and a bit slower. Will continue to forecast a drying trend,
and significantly lower humidity arriving by Wed with highs in
the 70s and lows Wed night and beyond into the 50s for most.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
As of 700 AM EDT Thursday...

Isolated to widely scattered showers continue well NW of RIC,
mainly dry but cloudy elsewhere. Mainly VFR this morning across
the SE, with IFR CIGs at SBY through 14-15Z. Mainly MVFR CIGs
continue into the aftn across the piedmont, while it will become
primarily VFR to the east. SE winds will avg 5-10kt today.
Widely scattered showers/tstms possible this aftn but coverage
along and E of I-95 is too low for any mention in the TAFs. Some
lowering of CIGs is expected again late tonight, with rain
chances increasing enough to include VCSH in the last 6 hr
portion of the 12Z TAFs.


Outlook: The precise impacts from Hurricane Helene and its
remnant low remains somewhat uncertain, but period of moderate
to locally heavy rain are likely Friday, with some gusty winds
possible (and locally higher winds possible in tstms late Fri
morning through Fri aftn). The widespread showers diminish in
coverage Fri night, with Sat being mainly dry. Unsettled WX with
daily chc for showers and a few storms Sun-Mon.

&&

.MARINE...
As of 405 AM EDT Thursday...

Key Messages:

- Small Craft Advisories have been extended into late Friday for all
Atlantic zones due to persistent seas above 5 ft.

- Southeast winds increase on Friday bringing the potential for
Small Craft conditions in the Chesapeake Bay, lower James River, and
Currituck Sound.

High pressure has moved off the eastern Canadian coast with
Hurricane Helene making northward progress into the eastern Gulf of
Mexico. Winds are generally E or SE at 5-10 kt across the local
waters. Waves are mainly 1-2 ft in the Chesapeake with 2-3 ft near
the mouth. Seas range from 3-5 ft, highest away from the immediate
coast.

Southeast flow has overspread the waters as high pressure well to
the north continues to translate eastward/offshore. This has allowed
near-shore wave heights to finally fall below 5 ft but have
maintained SCA headlines for all coastal waters as heights remain 4-
5 ft farther offshore. Hurricane Helene continues to intensify over
the extremely warm waters of the eastern Gulf. The storm is forecast
to make landfall along the Florida Big Bend early this evening.
Helene continues quickly north tonight into Georgia. SE winds 5-10
kt continue today and tonight before the gradient strengthens
locally on Friday. Winds increase to 15-20 kt with gusts to 25 kt on
Friday into Friday evening and SCA headlines are likely for the
Chesapeake Bay, lower James, and Currituck Sound. The gradient
relaxes early Saturday as the remnant circulation from Helene gets
shunted NW on the northern periphery of an upper level low. Waves in
the bay increase to 2-3 ft with 3-4 ft likely near the mouth Friday
afternoon and evening. Calmer conditions are expected on Saturday
and even the seemingly never-ending SCA headlines for the coastal
waters may even be allowed to expire. For now, have only extended
the ongoing coastal waters SCAs for an additional six hours into
Friday night with less confidence that 5 ft seas will persist toward
sunrise Saturday. Uncertainty increases for Sunday into next week
with the 00z GFS the most bullish on some of Helene`s energy
combining with the lingering upper low to result in the development
of another area of (non-tropical) low pressure along the NC coast.
Will show ENE winds increasing to around 15 kt for now pending
better agreement in the models.

High rip current risk continues for all beaches today and Friday
given 3-5 ft nearshore waves and swell periods 10-12 seconds.

&&

.TIDES/COASTAL FLOODING...
As of 405 AM EDT Thursday...

Key Messages:

-Tidal departures continue to fall across the region.

- Coastal flood advisories have been issued for the next two high
tide cycles for the tidal Potomac and Rappahannock as well as bay
side portions of the MD Eastern Shore.

Tidal departures continue to fall this morning, but remain highest
(1.5-1.75 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 have been issued through late this evening.
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. Latest guidance does show the potential for
increasing anomalies late Friday across the middle and upper bay
with the potential for minor to locally moderate coastal flooding at
Bishop`s Head and Lewisetta.

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

As of 405 AM EDT Thursday:

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

- Lewisetta (P.O.R. since 1979): 18 (with several more to come),
previous record was 8 in Oct 2021, Oct 2019, Oct 2015.

- Cambridge (P.O.R. since 1980): 13 (with this morning`s high tide
unlikely to reach minor flood), previous record was 5 in Oct 2021,
Oct 2019, Sep 2018, Oct likely 2011.

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

- Lewisetta (P.O.R. since 1979): 7 (with additional moderate flood
unlikely), ***tying the record of 7 in Oct 2015***

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory until 1 AM EDT Friday for MDZ021>023.
NC...None.
VA...Coastal Flood Advisory until 1 AM EDT Friday for VAZ075-077.
     Coastal Flood Advisory until 11 PM EDT this evening for VAZ076-
     078-085-521-522.
MARINE...Small Craft Advisory until 1 AM EDT Saturday for ANZ650-652-
     654-656-658.

&&

$$

SYNOPSIS...LKB
NEAR TERM...LKB/SW
SHORT TERM...LKB
LONG TERM...KMC/LKB
AVIATION...LKB/TMG
MARINE...RHR
TIDES/COASTAL FLOODING...