810
FXUS61 KAKQ 170756
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
356 AM EDT Sat Aug 17 2024

.SYNOPSIS...
Scattered showers and storms are possible through Monday as an upper
level trough moves into the area. Cooler and drier conditions are
expected from Tuesday through the rest of next week as high pressure
remains to the north of the local area under a trough aloft.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 320 AM EDT Saturday...

Key Messages:

- Warm and humid today with highs in the mid 80s.

-Chances for showers and thunderstorms today, a few of which may
 be strong to severe.

Early this morning, sfc high pressure is still located along
the E Coast. Flow aloft immediately over the local area is
roughly zonal, but a trough is positioned over the upper
Midwest. A weak disturbance is passing through the flow aloft,
allowing for a few showers, which are located in the piedmont
and near Fredericksburg Northern Neck as of latest radar. A chc
for showers will continue through the early morning hours for
much of the area.

Sfc high pressure gradually slides offshore today as low pressure
pushes east over the Great Lakes. Its trailing cold front will enter
the Ohio Valley. Meanwhile, TC Ernesto, well offshore, will pass by
the local coast. A short wave/lee trough ahead of the main front
will trigger showers and thunderstorms today. The morning will start
out with Chc PoPs (25-35%) across central portions of the FA. Precip
chances then increase and expand this afternoon. Highest
coverage/confidence is for areas N of I-64, where PoPs are in the 45-
60% range. Elsewhere, PoPs are in the 15-40% range. There is a
chance for a few storms to become strong to severe, primarily W of
I95. With highs in the mid 80s and dew points climbing into the low
70s, there will be sufficient instability. HREF mean MLCAPE reflects
1000-1500 J/KG with highest values in the piedmont. Shear will be a
demure 20-25kt. As such, there is a Marginal risk for western
portions of the area. The primarily threat would be damaging wind
gusts. Precip will shift focus to the NE portions of the FA after
sunset and into the overnight hours. Given southerly flow and
continued cloud cover, lows overnight will be a mild 70-72.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 355 AM EDT Saturday...

Key Messages:

-Seasonally warm and humid with daily chances for scattered
 showers and storms.

-Storms may be strong to severe Sunday (and to a lesser extent
 Mon).

The upper level trough moves over the area Sun providing synoptic
forcing sufficient for more widespread scattered showers and storms
during the afternoon and evening. In addition to the forcing aloft,
a cold front moves E towards the local area late Sun afternoon into
Sun night. Afternoon PoPs are now in the 55-70% for pretty much the
entire area. Precip will then taper off W to E in the
evening/overnight as the front moves through. Instability looks to
be a bit higher than Sat, with HREF mean MLCAPE showing values on
either side of 1500 J/KG across most of the area. HREF mean 0-6km
shear is showing 20-25kt. Given higher instability, greater forcing,
and decent shear (for mid August), expect the potential for
scattered strong to severe storms with damaging winds the primary
threat. SPC has a marginal risk (level 1/5) for the entire FA and
clips portions of NE NC in a slight (level 2/5) risk. While storms
should be moving given 20-25 kt+ of deep layer shear, cannot rule
out localized flooding, particularly if storms train over the same
areas. As such, WPC has areas N of I-64 in a marginal risk for
excessive rainfall Sat and the entire area under a marginal risk on
Sun. It will again be warm and humid on Sun with highs in the mid-
upper 80s and dew points in the low-mid 70s. Lows Sun night will be
in the upper 60s to low 70s.


The upper level trough remains over the area on Mon with a final
shortwave pushing through Mon afternoon into Mon evening.
Instability (MLCAPE of 500-1000 J/kg) will generally be lower but
still sufficient for widespread scattered showers and perhaps
isolated storms. Westerly sfc flow and limited shear will limit the
potential for severe weather. However, cannot rule out one or two
stronger storms with damaging wind gusts given strong low level
lapse rates that are anticipated. Thus, the SPC has place the local
area in a Marginal Risk. Highest coverage of storms will be in the
NW where PoPs are 50-60%. Elsewhere, PoPs are 35-50%. Highs on
Monday will be in the mid 80s. A touch cooler Mon night will lows
ranging from the low 60s inland to upper 60s at the coast.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 320 AM EDT Saturday...

Key Messages:

-Cooler, drier weather is expected next week.

A seasonally strong UL trough will be situated over the East Coast
next week. Cool high pressure at the sfc builds into the region from
the NW Tues, then gradually slides east through the week. This will
usher in a cooler, drier pattern. Temps looks to be well below
normal through Friday with highs around 80 Tues-Thurs and low 80s on
Friday. A decent portion of the area may not even exceed the upper
70s on Wed. Overnight lows look pleasantly cool as well with the mid
to upper 50s inland and low to mid 60s closer to the coast. Dew
points will drop into the 50s on Tues and stay there through Thurs,
then creep back up into the 60s Fri.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
As of 130 AM Saturday...

A weak disturbance moves through the area tonight into Saturday
morning. Showers may reach RIC overnight, but there is simply
not enough confidence to include in the terminal forecast beyond
VCSH. More likely, MFVR cigs will develop early Saturday
morning at RIC as low level moisture increases. However,
guidance suggests the reduced CIGS will be short lived as they
raise to VFR by 18z. Showers/storms are possible tomorrow
afternoon especially at RIC from the lee side trough. Southeast
winds of 5 to 10 kt tonight becoming southerly on Saturday.

Outlook: A slow moving cold front will approach from the west
Sunday into Monday with chances for scattered aftn/evening
showers/storms each day, especially Sunday. Storms may be strong
to severe on Sunday with gusty winds the primary threat.

&&

.MARINE...
As of 355 PM EDT Friday...

Key Messages:

- Small Craft Advisories are in effect for all coastal waters starting
  tonight north of Cape Charles, with the remaining coastal
  waters and the Mouth of the Bay starting on Saturday as swells
  from Hurricane Ernesto reach the coast.

- SCAs remain a possibility in the Bay Sat aftn/Sat night for southerly
  wind gusts of 20 - 25 kt with the best chance N of New Pt
  Comfort.

The area of high pressure that has been in place for the last several
days is gradually weakening and sliding off the New England Coast
this afternoon.  Meanwhile, a storm system over the Great Lakes is
making slow progress toward the Mid-Atlantic States today and will
take several days to move through the area, before departing early
next week.  Right now Winds are generally from S at 5-10 kt but are
stating to increasing from the S - SE. As the area of high pressure
slides offshore and the low pressure system approaches from the
midwest, expect to see enough tightening of the pressure gradient
for S winds 10-15kt with gusts to 20 kt tonight, and winds a little
higher Sat aftn/Sat night. SCA conditions from wind are possible in
the Ches Bay north of New Pt Comfort. Meanwhile, Hurricane Ernesto,
currently about 180 miles SW of Bermuda, is forecast to lift NNE,
over Bermuda by early Sat before heading into the North Central
Atlantic. Impacts locally will be restricted to increasing swell and
the threat for deadly rip currents. SCA flags start for the Atlantic
waters north of Cape Charles Light at 02z/10pm tonight, with the
remaining Atlantic waters and the mouth of the Bay starting SCAs by
Sat aftn. Seas Saturday will average 5-7 ft N of Cape Charles, and 4-
5 ft to the south, while then averaging 5-6 ft by late Sat night
through Sunday. Waves near the mouth of the bay will increase as
well, generally 2-3 ft on Saturday with 3-5 ft possible late Sat
night into Sunday before things start to calm down Monday (though
will likely have seas offshore linger at 4-5 ft possibly into early
Tuesday). The models are in decent agreement that another eastern
CONUS upper trough develops next week, allowing a cold front to move
through the local waters Mon night/Tuesday with winds shifting to
the N/NW. Current models do not show more than 10-15kt of wind Mon
night/Tue, but as the details become more precise, would expect
winds to be stronger given good mixing as rather cool air (by August
standards) moves over the warm waters.

&&

.TIDES/COASTAL FLOODING...
As of 420 AM EDT Friday...

Key Message:

-  A Moderate Risk of Rip Currents today, with a High Rip Risk
   likely for both Saturday and Sunday as long period swell from
   distant Hurricane Ernesto affects the region.

The latest 16/00Z run of the NWPS supports high rip risk for
all Atlantic coastal zones for the weekend given seas of 4-6 ft
with a dominant period of 13-15 seconds. Today begins low with
seas only 1-2 ft, but with the building seas to ~3 ft or 3-4 ft
this aftn, and an increase in the wave period, will have a
Moderate rip risk in effect today. Some minor tidal flooding
will be possible along the Bayside of the MD eastern shore by
Sun/Mon as the persistent long period swell may help trap water
in the Bay for several tide cycles (the southerly wind direction
favors transporting any trapped water northward).

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory from 10 PM this evening to 6 AM EDT
     Sunday for MDZ021.
NC...None.
VA...None.
MARINE...Small Craft Advisory from 1 PM this afternoon to 4 AM EDT
     Sunday for ANZ630.
     Small Craft Advisory from 4 PM this afternoon to 10 PM EDT
     this evening for ANZ631-632.
     Small Craft Advisory from 1 PM this afternoon to 6 AM EDT
     Monday for ANZ634.
     Small Craft Advisory until 6 AM EDT Monday for ANZ650-652-654.
     Small Craft Advisory from 10 AM this morning to 6 AM EDT
     Monday for ANZ656-658.

&&

$$

SYNOPSIS...RMM
NEAR TERM...AM
SHORT TERM...AM/RMM
LONG TERM...AM
AVIATION...AM/MRD
MARINE...ESS/LKB
TIDES/COASTAL FLOODING...