639
FXUS61 KAKQ 171907
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
307 PM EDT Wed Jul 17 2024

.SYNOPSIS...
An unsettled period begins late this afternoon through
Thursday, as a cold front pushes through the area and stalls
across the Carolinas. Shower chances focus mainly over southern
Virginia and North Carolina Friday, then return to all zones by
Saturday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 300 PM EDT Wednesday...

Key Messages:

- A Severe Thunderstorm Watch is now in effect for the northern
  half of the area through 10 PM.

- Heat Advisories remain in effect for the entire area through 8
 PM (other than the MD beaches).

- Showers/storms become fairly widespread this evening into tonight.

This afternoon, high pressure remains anchored well off the SE
coast to Bermuda. Meanwhile, a lee trough is in place just to
the east of the Blue Ridge and a cold front is well NW of the
region over portions of the Great Lakes/Ohio Valley.

The cold front remains well to the NW of the area into tonight,
with storms developing on the lee trough with strong low level
destabilization (ML CAPE ranging from 1500 to 2000 J/kg).
Mid level lapse rates are quite weak and with the hot humid
airmass, hail will be unlikely. Deep layer shear increases to a
modest 20 to 30 knots later this afternoon across the northern
half of the area as the mid level flow increases with the
approach of the upper trough. Storms will primarily be linear
clusters and somewhat disorganized, but a marginal supercell or
two cannot be ruled out, along with bowing segments. The primary
threat with the strongest storms will be damaging wind gusts.
SPC continues with the northern half of the forecast area in a
Slight Risk for severe weather and a Marginal Risk elsewhere
(technically only GEN thunder along the Albemarle sound). In
addition to the severe weather threat, there will also be a
localized heavy rain threat as moisture pools ahead of the
front, with PWATs surging to 2.2+", though the best chances for
widespread heavy rain into tonight are still expected to be
mainly north of the forecast area.

Showers/storms gradually diminish by or shortly after
midnight, with lingering showers and embedded storms possible
overnight (but with little SVR threat). Lows in the lower 70s NW
to the mid-upper 70s SE.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
As of 300 PM EDT Wednesday...

Key Messages:

- There is a heavy rain threat Thursday across portions of southeast
Virginia into northeast North Carolina where WPC has a Slight Risk
of excessive rainfall.

- There is a Marginal Risk of severe weather roughly along and south
of US-460 Thursday.

On Thursday, PoPs ramp back up in the mid/late morning as the actual
cold front pushes into the region, gradually moving south through
the day Thursday, before eventually stalling near the NC/VA border
Thursday night. Highest shower/storm chances will be focused across
the southern half of the area on Thursday. Locally heavy rainfall
will be possible, with a Day 2 Slight Risk ERO for far southern
Virginia and northeast North Carolina where much of the guidance is
forecasting in excess of 2" of QPF. The 12z HREF probability matched
means now have a large 50% contour for 3"/3hr centered over SE VA
into NE NC tomorrow afternoon/evening, with even a small 70% contour
over portions of NE NC. Based on the current trends, it is very
possible a Flood Watch will be needed for at least southside Hampton
Roads into northeast North Carolina, will let the overnight shift
make the final determination. There is a Marginal ERO for the
remainder of the forecast area, but expect shower to diminish in
coverage and intensity over the north by the late afternoon.

Will also need to watch the severe weather potential on Thursday
afternoon with a few of the CAMs being quite aggressive. There will
again be plenty of instability tomorrow, with ~2000 to 3000 J/kg of
MLCAPE in place across the region despite the clouds. We will also
have more effective shear over the area compared to today, with 30-
40 knots possible. The primary hazard tomorrow with any stronger
storms will again be damaging wind gusts, with the hail threat
remaining limited due to weak mid-level lapse rates. If we can fully
destabilize, as some of the CAMs have been showing, there is
the potential for a corridor of greater damaging wind potential.
For now, SPC has roughly along and south of US-460 in a
Marginal Risk for severe weather.

The front pushes just south of the local area Thursday night into
Friday, with the highest rain chances confined to the southern
areas. With some clearing and drier air/lower dew pts, lows Thu
night drop into the low-mid 60s NW, with lower 70s SE (where its
stays humid with more clouds). Drying out for the northern half of
the area Friday, with only scattered shower and storm chances by
Friday afternoon (over the south). Partly sunny N and mostly cloudy
S with high temperatures mainly in the low-mid 80s (more comfortable
N and central where dew pts will be in the 60s).

The upper trough moving into New England looks to flatten out later
Friday while the area of high pressure off the Southeast coast
begins to gradually retrograde back westward slightly. The front is
forecast to lift back north into the southeastern portion of the
area and stall out into Saturday. The best rain chances Friday night
will be across northeast North Carolina in the vicinity of the
boundary, then chances spread back north on Saturday as the front
shifts. The higher rain/storm chances on Saturday will be south of
the I-64 corridor.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 300 PM EDT Wednesday...

Key Messages:

- Daily rain chances persist as the front lifts back north and
stalls over the southeastern portion of the area.

- Temperatures look to stay near normal.

A positively tilted trough will start to dip down into the mid
Mississippi Valley on Sunday allowing our flow to become more
southwesterly. The stalled front won`t move very much, but it does
become a bit more diffuse on Sunday so generally should see rain
chances focus in the aftn/evening rather than all day. Variable
cloudy and a bit warmer with highs in the mid 80s to around 90F.
Remaining a bit unsettled into early next week, with the southern
and western portions of the area having the best chance for
rain/storms. After a brief, partial break from the humidity
(especially up north), 70+ degree dewpoints will stream back into
the area for this forecast period making it feel humid once again.
The somewhat good news is that temperatures aren`t expected to be
nearly as hot during the extended period as they have been, with
high temperatures Mon-Tue forecast to top out in the mid to upper
80s to near 90F, which is right around or even slightly below normal
for this time of year.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
As of 200 PM EDT Wednesday...

Scattered showers and thunderstorms develop later this
afternoon through this evening, bringing localized sub-VFR
conditions. The best thunderstorm chances are initially focused
near ts Albemarle Sound, with VCTS at ECG. Otherwise, scattered
showers and storms will mainly be W of the terminals until late
in the afternoon, have mention of VCTS starting in the 22-00Z
timeframe, with prevailing SHRA at all but ECG starting ~00Z and
thereafter into tonight. Overall, SHRA/TSRA diminish overnight.
Gusty winds, frequent lightning, and heavy rain will be
possible with any storms, with IFR- LIFR flight restrictions in
VSBY. Gusty winds in excess of 40kt will be possible in the
storms as well, especially at RIC/SBY. Showers and storms taper
off from W to E later tonight as forcing weakens. The cold front
lags back to the NW into Thu morning, then pushes S through the
FA on Thu with scattered to numerous showers and storms
redeveloping. Periodic flight restrictions (mainly VSBYs) are
expected due to locally heavy rain along with gusty winds.

Outlook: The front will push farther S Thu night into Friday as
drier air pushes in from the NW. The boundary lifts back N
Saturday. The chance for showers/tstms is less Friday (except
over far SE VA/NE NC) and then increases again Saturday. Sunday
will see scattered, mainly aftn/evening showers/storms.

&&

.MARINE...
As of 300 PM EDT Wednesday...

Key Messages:

- Small craft advisories in effect for the Chesapeake Bay and
northern coastal waters this evening into early tonight. A severe
thunderstorm watch is also in effect for the upper bay and northern
coastal waters through 10 PM.

- Additional showers and storms expected Thursday.

- Calmer marine conditions return Friday through the weekend.

Bermuda high pressure is situated well offshore this afternoon,
leading to SW flow across all of the waters. A cold front is also
located well to our NW, extending from the nrn Great Lakes into the
Mid MS River Valley. Winds are averaging around 15 kt, though a few
sites are in the 15-20 kt range. With a tightening pressure gradient
and convection approaching from the W, winds are forecast to
increase to 15-20 kt areawide this evening into tonight, with gusts
to ~25 kt. This will also push seas in the northern waters to 4-5 ft
(6 ft possible out near 20 nm). Have continued SCA headlines for the
ocean N of Cape Charles and introduced new SCAs for the Chesapeake
Bay starting at 4 PM this afternoon. While the duration of these
winds are uncertain, local wind probabilities are >50% for 18 kt
sustained winds and 25 kt gusts for most of the central/upper bay.
Waves of 2-3 ft are also expected. For now, the SCA goes through 10
PM over the bay and through most of tonight for the northern coastal
waters. S of Cape Charles, seas look to stay below 5 ft and wind
gusts should remain just shy of 25 kt; thus, continue to hold off on
SCAs here. Later this evening, convection may complicate these
prevailing winds and there is the potential for strong-severe wind
gusts of 40-50+ kts. A severe thunderstorm watch is also in effect
for the upper bay zone (ANZ630) through 10 PM. Winds subside around
sunrise Thursday as the gradient slackens and the cold front begins
to enter our area. The front then briefly stalls over the waters Thu
afternoon, allowing winds to begin rather variable. This front will
also serve as a focus for widespread showers and storms, especially
across the the srn bay and coastal waters. Strong to severe wind
gusts are again a possibility, in addition to heavy rain and
frequent lightning. ~10 kt of E/NE flow is expected Friday, shifting
to the SE Saturday. Seas and waves of 2-3 ft and 1-2 ft are expected
beyond Thursday, respectively.

With the southerly flow and 3-4 ft nearshore waves, the rip risk
remains moderate for the northern beaches today and at least for the
first half of the day Thursday. A low risk is forecast through today
and Thursday across southern beaches. Note that continued S/SW flow
may exacerbate upwelling conditions, leading to much cooler-than-
expected water temperatures (low-mid 60s) in the surf zone.

&&

.CLIMATE...
A record high min temperature was tied yesterday/Tue 7/16 at
SBY. Records are listed below for today/Wed 7/17. Record highs
are unlikely and although record high mins may be challenged,
showers and storms late in the day/tonight may lead to calendar
date mins lower than what is observed this morning.

- Record Highs:

- Site:  Wed 7/17

- RIC:   100 (1980)
- ORF:   100 (1887)
- SBY:    99 (2012)
- ECG:    99 (1942)

- Record High Mins:

- Site:   Wed 7/17

- RIC:    76 (2005)
- ORF:    80 (2021)
- SBY:    80 (1983)
- ECG:    80 (2019)

- Highest 1-hr Heat Index Value on record (P.O.R. 1948-2024):

- RIC:   117 (7/17/1980)
- ORF:   118 (8/18/2017)
- SBY:   122 (7/15/1995)
- ECG:   119 (7/5/1999)

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Heat Advisory until 8 PM EDT this evening for MDZ021>024.
NC...Heat Advisory until 8 PM EDT this evening for NCZ012>017-
     030>032-102.
VA...Heat Advisory until 8 PM EDT this evening for VAZ048-060>062-
     064>069-075>090-092-093-095>100-509>525.
MARINE...Small Craft Advisory until 10 PM EDT this evening for
     ANZ630>632-634.
     Small Craft Advisory until 7 AM EDT Thursday for ANZ650-652.
     Small Craft Advisory until 4 AM EDT Thursday for ANZ654.

&&

$$

SYNOPSIS...AJB/LKB
NEAR TERM...AJB
SHORT TERM...AJB/LKB
LONG TERM...AJB/LKB
AVIATION...AJB
MARINE...SW
CLIMATE...