716
FXUS61 KLWX 171421
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1021 AM EDT Tue Sep 17 2024

.SYNOPSIS...
Low pressure over the Carolinas will gradually weaken through
Wednesday. Another low may develop off the coast during the second
half of the week. A backdoor cold front may push into the area
Saturday. Strong high pressure will build northeast of the area
in its wake.

&&

.NEAR TERM /THROUGH TONIGHT/...
1030 AM Update: Low clouds will continue to cover the forecast
area, especially further south into central VA where the
proximity to the low pressure system in NC is closer. Isolated
to scattered showers will continue to inch further north
throughout the day with the best chances for rain across central
VA and parts of the lower Allegheny Front. Highs will continue
to climb into the mid to upper 70s across areas east of the Blue
Ridge, with slightly cooler temps further south and west where
more rain and cloud coverage will reside.

Previous Discussion Follows:
Low pressure over west-central North Carolina
will continue to move toward the northwest today and tonight.
Patchy drizzle or occasional rain showers could bring a few
hundredths to one tenth of an inch with isolated one half inch
amounts along I-66 and areas to the north through tonight. South
of I-66 and toward the I-64 corridor, rain amounts could ramp
up more quickly over the next 18 hours or so with the low
pressure system not too far to the south. Rain amounts could
average one quarter to one half inch with isolated one and a
half inches through tonight in these areas.

High temperatures with range from near 60 to lower 60s at highest
elevations in the west to the upper 70s to near 80 in the east and
near the Chesapeake Bay. Lows tonight in the middle 50s in the west
and the lower to middle 60s in the eastern zones.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The low pressure system will move over the southern Appalachians of
western North Carolina and eastern Tennessee Wednesday into
Wednesday night. This combined with additional waves of mid-level
energy rotating into the low from the north will generate additional
rain showers and perhaps a few rumbles of thunder Wednesday and
Wednesday evening. Additional rain amounts could average one half to
one inch with isolated 2 to 3 inch amounts. Higher amounts could
occur in southwest zones of the Virginia Piedmont, central Blue
Ridge Mountains and central Shenandoah Valley. All of this
anticipated rain will rely heavily on the intensity of the main low,
additional moisture from the east and additional energy from the
north. The placement of the main low will also have an impact as to
who gets the most rain. Highs Wednesday upper 60s to lower 70s in
the west and middle 70s in the east. Lows middle 50s in the west to
middle 60s in the east.
Winds will become more
northeast Wednesday, then more northerly while diminishing on
Thursday.
The threat for showers and any thunderstorms on Thursday into
Thursday evening diminishes from northwest to southeast. As a matter
of fact there could be some partial clearing skies from west to east
Thursday afternoon. Highs will be a little warmer with temperatures
in the lower 70s west and near 80 east.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
There`s been a notable shift in 00Z guidance compared to 24 hours
ago with respect to the upper level pattern for Friday into the
weekend. At least at the moment, the theme is consistent amongst
ensembles per cluster analysis. The ridge/trough orientation is now
situated such that the trough axis remains offshore, and if it does
cut off, does not result in a closed low retrograding over the
southeastern states. The backdoor cold front is still forecast to
push into the area Saturday as a strong trough moves across eastern
Canada, but this appears to bring about a drying/cooling trend as
strong high pressure builds to the northeast. Winds maintain more of
a northeasterly trajectory such that maritime moisture does not
rotate back inland. With all that said...low pressure will likely be
positioned somewhere offshore, so if there were to be more clouds
and/or rain chances, it would likely be across eastern parts of the
forecast area. Temperatures will be near or above normal Friday,
becoming below normal by Sunday.

Model spread increases Monday. High pressure may hold strong,
although warm frontal processes may be nearing the Appalachians.
Temperatures will likely remain a little below normal.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Patchy drizzle and occasional showers could bring IFR conditions to
the terminals today with a better emphasis of IFR conditions
due to lowered ceilings near CHO moreso. The best chance for IFR is
through 18z today then again tonight.

Rain showers will likely continue off and on Wednesday with low
pressure nearby. Winds northeast to east 5 to 15 kts through
Wednesday. Gusts of 20 to 25 kts are possible mainly each
afternoon and evening, especially at terminals close to the
waters and along the ridges. With the residual low pressure
nearby, expect periods of sub-VFR conditions.

Underneath a mid-level low pressure system on Thursday, scattered
showers may develop across the area. Clouds should be abundant
which may afford periods of sub-VFR conditions.

Chances for notable weather seem to be decreasing Friday and
Saturday, with VFR conditions now looking most likely. However, will
have to keep an eye on offshore low pressure. Northeasterly winds
may gust to around 20-25 kt Saturday.

&&

.MARINE...
SCA conditions will continue today. This is in association with
a tightened pressure gradient from blocking high pressure to
the north and low pressure moving inland across the coastal
Carolinas. At this time, the risk of gale force winds appears
low, though some gusts around 30 knots have been observed over
the mid bay. As a weakening area of low pressure tracks through
the area, winds will be out of the east on Wednesday while
likely remaining at SCA levels for at least portions of the
waters. Winds will become more northeast Wednesday, then more
northerly while diminishing on Thursday.

North to northeast winds continue Friday into Saturday. As long as
low pressure remains sufficiently offshore, sub-advisory conditions
would occur Friday. A backdoor cold front may introduce stronger
winds at some point between Friday night and Saturday night.
Advisories may be needed depending on the timing of the front.

&&

.TIDES/COASTAL FLOODING...
With low pressure inland over the Carolinas and winds from a
northeasterly direction, there have not been significant rises
in anomalies, with the highest values greater than one foot
along the Potomac. Advisories remain in effect, but most
flooding will be marginal. Have not extended advisories since
anomalies may drop slightly tonight into Wednesday. 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 until 10 PM EDT this evening for DCZ001.
MD...Small Craft Advisory until 6 AM EDT Wednesday for MDZ008.
     Coastal Flood Advisory until 10 PM EDT this evening for MDZ014.
     Coastal Flood Advisory until 6 PM EDT this evening for MDZ016-
     018.
VA...Coastal Flood Advisory until 10 PM EDT this evening for VAZ054.
     Coastal Flood Advisory until 6 PM EDT this evening for VAZ057.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT Wednesday for ANZ530>534-
     536>543.
     Small Craft Advisory until midnight EDT tonight for ANZ535.

&&

$$

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