753
FXUS61 KLWX 210139
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
939 PM EDT Sun Sep 20 2026

.WHAT HAS CHANGED...
Hourly trends have been updated through the night based on
latest radar and model data. Portions of the Small Craft
Advisory now start at 3 AM.

&&

.KEY MESSAGES...
- 1) Rounds of showers and decreasing temperatures through
  Tuesday.

- 2) Cool & wet conditions persist through the end of the week,
  with drier conditions heading into the weekend.

&&

.DISCUSSION...
KEY MESSAGE 1...Rounds of showers and decreasing temperatures
through Tuesday.

Showers have been much less common than earlier CAM runs
suggested. This is changing as of mid evening, with showers
along the surface cold front sinking southward from
Pennsylvania, and a few additional showers near the bay where
there is increasing convergence and slightly higher instability.
Most of these showers should dissipate or exit around midnight
to 2 AM. Additional showers and thunderstorms currently over
the Ohio Valley will move toward the area the second half of the
night. The highest chance of rain will obviously be along the
Allegheny Mountains, with some uncertainty how well and showers
hold together farther east. In between the rounds of showers and
lower clouds advecting from the north, some patchy fog could
develop where there is clearing.

More showers may arrive in the west toward daybreak as the next
shortwave-trough and weak area of low pressure approaches the
area. However, there is considerable model spread on the timing
and coverage of any rain during the daylight hours of Monday.
The period of heaviest rainfall looks to be Monday night/early
Tuesday when onshore flow/moisture advection is strongest
combines with a weak low to mid-level low pressure.

High pressure then builds south from the Northeast Tue setting
up a strong cold air damming event supporting well below normal
temperatures, cloudy conditions, and additional periods of rain.


KEY MESSAGE 2...Cool & wet conditions persist through the end
of the week, with drier conditions heading into the weekend.

Intermittent showers remain possible mid-to-late week as a
lingering frontal boundary sags to the south. Additionally, a
strong coastal low begins to track north close to the Maryland
coast Thursday and into Friday, which will bring gusty
conditions to the region. This strong onshore flow could bring
minor coastal flooding to sites along the Chesapeake Bay. See
the coastal flooding section below for more information.

As this coastal low tracks to the north, dry mid-level air from the
upper Midwest moves in overhead. This will create somewhat drier
conditions heading into the weekend, although there is a bit of
model discrepancy on how slow the coastal low will be moving out of
the area. Winds could stay elevated until this system is well north
of the Mid-Atlantic. Temperatures stay slightly cooler-than-average
during this time, although gradually increase near the end of the
week as any lingering shortwave disturbances track offshore.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
Some notable changes were made to the 00Z TAFs. First, showers
have been less common early this evening, though a more
concentrated ribbon of showers along a cold front is approaching
from the north. Confidence in rain is highest at MRB/BWI/MTN,
with decreasing chances to the south. This will also bring a
wind shift to the NW to N. The second change was to be more
conservative with the ceiling forecast through Monday. This is
largely based on BUFKIT moisture profiles. In fact, the period
of MVFR ceilings behind the front overnight into early Monday
could actually be pretty brief, except at CHO. Before these
ceilings arrive, some fog may develop at CHO, but this is
uncertain and dependent on cloud breaks. Believe the metro
terminals should improve to VFR by late Monday morning if not
earlier. The one caveat is if more widespread rain moves into
the area Monday. That could reduce ceilings and visibilities,
with the greatest chance of that happening at MRB. Some models
maintain dry conditions through the day, which is why PROB30
groups were utilized in the metro areas and at CHO. There does
appear to be greater consensus on rain and IFR conditions moving
into the area at some point Monday evening.

Once IFR cigs develop Monday night, there will likely be little
break through mid week as a cold air damming pattern develops.
Rounds of rain and drizzle will reduce visibility at times.

Intermittent sub-VFR conditions likely continue through Thursday as
additional showers move through the Mid-Atlantic, reducing CIGs and
VSBYs. Conditions potentially improve somewhat on Friday as a trough
moves north out of the region. Gusty winds remain a possibility
through the end of the week due to onshore flow, with gusts between
15-25 knots possible. Winds flow north to northeasterly.

&&

.MARINE...
Gusty outflows from a ribbon of showers are possible over mainly
the northern part of the bay this evening. These showers mark a
cold frontal passage, which will bring a wind shift to the
north. A bit of a pressure surge arrives the second half of the
night, so started the Small Craft Advisory at 3 AM for the
portion north of Drum Point. Overall this advisory looks
marginal though, with wind gusts above 20 kt unlikely. Winds are
expected to subside briefly Monday afternoon but then strengthen
Monday night through early Thursday. Additional SCAs will be
needed. High end SCA to near gale conditions are possible by
Wednesday as low pressure develops off the coast.

Wind gusts will be strongest on Thursday over the Bay as a coastal
storm tracks to the north off the East Coast. Sustained winds
between 20-25 knots are possible with as winds flow northeasterly.
Winds stay elevated on Friday, flowing due north. On and off showers
are possible over the waters as multiple shortwave disturbances move
through.

&&

.TIDES/COASTAL FLOODING...
Water levels remain elevated this evening but are starting to
drop slightly. This may mean any minor flooding at Annapolis
overnight is only near the threshold at most. Stronger NNE
winds Monday afternoon will push the water south into the mouth
of Chesapeake Bay. This excess water is expected to slosh back
mid week resulting in widespread minor coastal flooding, perhaps
moderate at Annapolis.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory until 6 AM EDT Monday for MDZ014.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 3 AM to noon EDT Monday for
     ANZ531>533-539>541.
     Small Craft Advisory from 6 AM to noon EDT Monday for ANZ534-
     543.

&&

$$

DISCUSSION...ADS/LFR/SRT
AVIATION...ADS/LFR/SRT
MARINE...ADS/LFR/SRT