842
FXUS61 KAKQ 171058
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
658 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 /12Z SATURDAY THROUGH WEDNESDAY/...
As of 655 AM Saturday...

A weak disturbance has triggered isolated showers this morning,
but these look to generally stay away from the terminals. More
likely, MFVR cigs will develop this 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 this afternoon especially at RIC from the lee side
trough. Light southerly winds this morning pick up this
afternoon, becoming breezy near the coast. Winds diminish again
tonight.

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 415 AM EDT Saturday...

Key Messages:

- Small Craft Advisories are in effect (or go into effect later
  today) for all coastal waters and for the mouth of the Bay
  as swells from Hurricane Ernesto reach the coast.

- SCAs go into effect later today into tonight for a surge of
  southerly winds gusting to 20-25 kt (generally the highest
  winds will be north of Windmill Pt with the headline quite
  marginal south of Windmill Pt).

The pressure gradient tightens a bit later today with high
pressure well offshore and low pressure tracking through the
Great Lakes, enough to raise SCAs for wind gusts of 20-25 kt in
the Bay. It will be quite marginal and of shorter duration over
the lower/mid Bay zones, with a longer period event N of
Windmill Pt where some gusts to 25 kt are expected. Elsewhere,
the SCA headlines will be primarily due to waves/seas meeting
criteria (seas 6-7 ft northern coastal waters and 4-5 ft
southern waters). By late tonight and Sunday, the southerly wind
surge weakens in the Bay with SCAs ending, but with the
headlines continuing through Sunday night/Monday for the coastal
waters and the mouth of the Bay. Sub-SCA conditions are expected
all zones by later Monday as seas drop to 4 ft or less.

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 show some timing differences with
the NBM winds a bit washed out, peaking at 10-15 kt. However,
given given good mixing as rather cool air (by August standards)
moves over the warm waters, expect there will be a surge at
least into the 15-20kt range with higher gusts when the models
can come to a consensus on timing. Winds then become NE at
10-15kt by midweek as high pressure centers a bit N of the local
area.

&&

.TIDES/COASTAL FLOODING...
As of 430 AM EDT Saturday...

Key Message:

-  A High Risk of Rip Currents today and Sunday for all beaches
   with nearshore waves of 5-6 ft north and 3-5 ft south
   combined with long period swell averaging 14 to 15 seconds
   today and 12-13 seconds on Sunday.

The latest 17/00Z run of the NWPS supports high rip risk for
all Atlantic coastal zones for the weekend given seas of 5-6 ft
N and ~4 ft S today with a dominant period of 13-15 seconds. On
Sunday, all areas can expect waves of at least 4-5 ft with a
dominant period in the 12-13 second range. Monday will start to
see gradual improvement, though there will likely be a high rip
risk with waves still at least 3 to 4 ft and a dominant period
of 10-12 seconds.

Currents at the mouth of the Bay have been primarily flood tide
dominant over the past 2 cycles, with water levels increasing
across the upper Bay. Given an elevated southerly wind through
tonight, have raised a Coastal Flood Advisory for Dorchester MD
for the high tide cycle late tonight/early Sunday morning
(latest TWL forecast has both Cambridge and Bishop`s Head
reaching at or above 3.5 ft MLLW). Will need to monitor trends
in the northern Neck and into Wicomico/Somerset MD later today
(these places could approach or reach minor flood thresholds
tonight if the water levels over-perform).

&&

.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 4 PM 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...LKB
TIDES/COASTAL FLOODING...