915
FXUS61 KLWX 161450
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1050 AM EDT Mon Sep 16 2024

.SYNOPSIS...
High pressure to the northeast will begin to retreat today.
Meanwhile, low pressure will move into the Carolinas through
Tuesday before weakening during the middle of the week. Another
low may develop off the coast toward the end of the week, with a
backdoor front approaching this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Dry conditions continue today although low and mid level clouds will
increase as Potential Tropical Cyclone Eight moves into the NC/SC
coast. The Potential Tropical Cyclone (low pressure system) is
currently located off the SC coast and is expected to move onshore
later this afternoon in the vicinity of the NC/SC border (between
Georgetown, SC and Wilmington, NC. Moderate to heavy rain has
already (as of 10:30am) pushed into these regions with the
northern extent of the rain shield pushing toward
Raleigh/Greensboro, NC. This activity is fairly light in nature
and will gradually fill in through late morning into midday
with the far northern reach of the rain shield reaching into
southern and southwest VA later this afternoon. PWATS per the
12z IAD sounding remain around 0.53 inches which is almost a
0.25 inch from where were on the 00z IAD sounding yesterday at
0.78 inches. Similar values can be found on the 12z RNK sounding
from this morning although a bit more moisture is noted in the
mid to upper levels of the atmosphere since the influence of the
blocking high to the north is farther away.

With all that said, moisture will continue to build across the
region today especially in areas along and south of I-66/US-50.
These locations could see a few spotty showers or areas of patchy
drizzle/mist later this evening into the front half of the overnight
period. It`s really not until Tuesday morning into Tuesday afternoon
when more widespread rain chances move into the region. Most of us
will see a continuation of BKN-OVC skies this afternoon and evening
with perhaps a little drizzle making it as far north as central
Virginia. Areas of drizzle are likely north of I-66/US-50 late
tonight into Tuesday morning with light to moderate showers pushing
into central VA and the Shenandaoh Valley. PWATS will likely
increase into the 1.0-1.5" range this evening before hopping up into
1.25-1.75" late tonight into Tuesday. No flooding is expected given
antecedent drought concerns. Rain amounts through Tuesday will
range between a tenth to a half an inch areawide. Heaviest
totals of a half to one inch can be found across the central
Blue Ridge and Shenandoah Valley due in part to upslope
enhancement.

Outside of the rain will be the wind. Gusts up to 30 mph are
possible along the higher ridges of the WV/VA Highlands and
central Blue Ridge. Elsewhere gusts of 15 to 20 mph are possible
especially in areas along the waters.

Little to no heating is expected today with minimal breaks of
sunshine. Highs today will reach into the mid to upper 70s east of
the Blue rIdge with upper 60s and low 70s further west. Lows tonight
in the low to mid 60s with a few low 50s in the western
mountains.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Rain showers and the isolated thunderstorm threat will continue and
likely spread north and east during the day Tuesday as the low
pressure system moves into the western Carolinas and becomes nearly
stationary. Rain showers and isolated thunder could linger Tuesday
night through midweek, including the Wednesday night timeframe.
Average rain amounts Monday night through Wednesday night could
average one half to one inch across the northern 2/3rds of the
region, while the southern 1/3rd, including along and east of the
Blue Ridge could encounter rain amounts in the one and a half to as
much as 3 inches of rain. Local amounts could reach up to 5 or 6
inches of rain depending on the model and the track and movement of
the low pressure system. A lot may change within the forecast as the
forecast track becomes more apparent. Continue to monitor our
forecast locally as well as the National Hurricane Center.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Uncertainty remains high for the extended period due to a blocky
upper level pattern. For Thursday and Friday, any remnant of the
previous coastal low will be weakened if not dissipated, and the
mid/upper low may also weaken and open into a trough. However,
secondary low pressure development could take place off the coast.
Shower chances will persist through this period thanks to the upper
trough, but may be comparably lower Friday as forcing weakens and
the trough axis perhaps aligning just east of the area. Temperatures
will be near normal.

For Saturday and Sunday, ridging will amplify northwest of the area
while a trough moves across the Canadian Maritimes. This combination
may result in another upper low closing off over the southeast US.
At the surface, a backdoor front will push toward the region, but
lose definition as it encounters a staunch coastal front along the
southeast coast. Strong high pressure over New England may result in
a good southward push however. It`s still unclear whether drier air
will be able to work into the area behind the front, or if clouds
and continued light rain chances persist. Temperatures will trend
below normal however.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Low clouds could reduce ceilings to MVFR status this morning. Brief
IFR can`t be ruled out as moisture has increased in the region.
MVFR/IFR CIGs likely tonight. Rain moves in Tuesday with IFR ceiling
restrictions likely at times. Rain likely continues through Tuesday
night before diminishing Wednesday afternoon. Winds will remain E/NE
5-15 kts. With the residual low pressure nearby, expect periods of
sub-VFR conditions, particularly on Wednesday.

Sub-VFR conditions may continue into Thursday, but there is
potential for some improvement as low pressure weakens. Showers will
remain possible however. Friday stands a better chance to see VFR
conditions and lower rain chances...perhaps even some clearing.

&&

.MARINE...
SCA conditions will remain possible this morning, mainly across the
southernmost waters, then become increasingly likely tonight into
Tuesday morning as gradient tightens in response to approaching
coastal low and high pressure to the north. At this time, the risk
of gale force winds appears low. As a weakening area of low pressure
tracks through the area, winds will be out of the east on
Wednesday.

Northeasterly winds will continue Thursday and Friday. With a weaker
pressure gradient now forecast for Thursday, winds may remain below
advisory criteria. The potential for advisories may return Friday
depending on low pressure development off the coast.

&&

.TIDES/COASTAL FLOODING...
Onshore flow strengthens through Tuesday morning with minor
coastal flooding becoming increasingly likely. However, surge
guidance has been trending downward, perhaps due to the low
remaining farther south and winds a touch weaker and more from a
northeasterly direction. Advisories remain in effect but may
need adjustments. Moderate flooding is much less likely now.
However, between the full moon and continued onshore flow, tide
levels will likely remain elevated and near minor flood
thresholds much of the week.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory from 5 PM this afternoon to 10 PM EDT
     Tuesday for DCZ001.
MD...Small Craft Advisory until 6 PM EDT Tuesday for MDZ008.
     Coastal Flood Advisory from 2 AM to 10 PM EDT Tuesday for
     MDZ014.
     Coastal Flood Advisory until 6 PM EDT Tuesday for MDZ016.
     Coastal Flood Advisory from midnight tonight to 6 PM EDT
     Tuesday for MDZ018.
VA...Coastal Flood Advisory until 6 PM EDT Tuesday for VAZ057.
WV...None.
MARINE...Small Craft Advisory until 6 PM EDT Tuesday for ANZ530>534-
     536>543.
     Small Craft Advisory from 2 PM this afternoon to 6 PM EDT
     Tuesday for ANZ535.

&&

$$

SYNOPSIS...ADS/EST
NEAR TERM...EST
SHORT TERM...KLW
LONG TERM...ADS
AVIATION...ADS/KLW
MARINE...ADS/KLW
TIDES/COASTAL FLOODING...LWX