549
FXUS61 KLWX 171829
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
229 PM 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/...
Low pressure over west-central North Carolina will continue to
move toward the northwest today and tonight. 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.
It is a tricky forecast for rainfall totals through tonight and
into early Wednesday. For areas north of I-66, a general swath
of a few hundredths of an inch to half an inch are expected.

Further south, totals will be higher where the rainfall will be
heavier and more steady. Guidance has continued to hint at two
relative maximums across the forecast area, 1) the eastern
slopes of the Blue Ridge and 2) across portions of central VA
into northern VA. The first area is more terrain induced whereas
the second area of interest is where the low-level jet likely
sets up late tonight and into early Wednesday. There may be a
localized area of 1-2" across that area. Cannot rule out higher
amounts across the eastern slopes of the Blue Ridge. For now,
isolated instances of flooding remain possible later tonight and
into Wednesday, especially across areas along/south of I-66 and
along/east of the Blue Ridge. 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. 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 aforementioned low pressure will continue to move across
western NC and further west on Wednesday. Rain will continue
through most of the day for a large portion of the area, with
the VA Piedmont likely receiving the most precipitation.
Additional totals of 2-3" are certainly possible through the day
on Wednesday as the low begins to break down and a coastal low
forms off the Delmarva. Cannot rule out a rumble of thunder in
the afternoon hours but overall convective activity should be
fairly suppressed. Highs top out in the upper 60s to low 70s
along and west of the Blue Ridge where the more cooler side of
the low resides and a few degrees warmer further east towards
the waters. Overnight lows Wednesday night drop down into the
mid to upper 50s along the Allegheny Front and low 60s further
east.

As the coastal low begins to shift further northeast, expect
shower chances to decrease from west to east during the day on
Thursday. There may be some general clearing later in the day.
Highs will top out in the upper 70s to near 80 for most areas.
Northwesterly flow will allow temperatures to drop down into the
upper 40s to low 50s along portions of the Allegheny Front
Thursday night, with mid to upper 50s more common further east
with low 60s near the waters.




&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Long term period continues to trend drier as model guidance keeps
the trough axis offshore. A backdoor cold front is set to drop
through the forecast area Friday afternoon and throughout the day on
Saturday as an upper level trough deepens over Canada into New
England. Cooler and drier air will move in with temperatures
expected to stay below normal. High pressure will keep conditions
primarily dry with a low pressure system off the coast of the
Carolinas leading to slight chance of PoPs in the southeastern
portions of the area through Monday. Precipitation chances increase
elsewhere on Monday as a low pressure system approaches from the
west.

High temperatures will be in the upper 70s to low 80s on Friday with
higher elevations staying in the mid to low 70s. Temperatures cool
slightly each day with high temperatures on Monday expected to be in
the low to mid 70s for most. High elevations will stay in the upper
50s to 60s. Overnight low temperatures will be in the 50s for most
each night with metro areas staying in the low 60s.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Occasional light to moderate showers could bring IFR conditions
to the terminals today with a better emphasis of IFR conditions
due to lowered ceilings near CHO. Better chances for IFR
conditions will be later 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 MVFR to IFR 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.

Prevailing VFR conditions are expected Friday and Saturday with dry
conditions at all terminals. Northeasterly winds on Friday shift to
easterly on Saturday.

&&

.MARINE...
SCA conditions will persist through the day 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. 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.

Northeasterly winds are expected to stay below SCA criteria on
Friday with winds gusting 10 to 15 knots. Winds shift more easterly
on Saturday with Small Craft Advisories likely as winds gust 15 to
20 knots.

&&

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