882
FXUS61 KLWX 210806
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
406 AM EDT Mon Sep 21 2026

.WHAT HAS CHANGED...
A Small Craft Advisory was issued for tonight through Tuesday
night.

&&

.KEY MESSAGES...
- 1) Cloudy and cooler conditions are expected through mid-week,
  along with daily chances for showers.

- 2) Daily shower chances, abundant cloud cover, and cool
temperatures continue through Thursday. Drier this weekend.

&&

.DISCUSSION...
KEY MESSAGE 1...Cloudy and cooler conditions are expected through
mid-week, along with daily chances for showers.

As of 330 AM, current radar imagery shows a weakening MCS
approaching from central West Virginia. Cloud tops have shown
substantial warming over the last couple hours. This complex of
storms is expected to continue weakening into showers as it
tracks eastward into our area, where northerly flow behind a
cold front is gradually advecting more stable air in. It`s
plausible that at least showers will persist into locations to
the west of the Blue Ridge this morning. Questions remain
regarding whether these showers will hold together further east.
Regardless, conditions will be mostly cloudy today. Temperatures
will be cooler than previous days, and conditions will also be
less humid, with dewpoints dropping into the 60s. There could be
a substantial gradient in temperatures from northwest to
southeast today. Western Maryland and the West Virginia
Panhandle will likely struggle to climb out of the 60s with
thick cloud cover and higher coverage of showers. Locations
along and east of I-95 may make it into the upper 70s to near 80
with lower coverage of showers and a few more breaks in the
cloud cover.

High pressure already in place to our north across southern
Quebec will rapidly strengthen from the upper 1020s hPa today
to near 1040 hPa by tomorrow night. As this occurs,
northeasterly flow will strengthen and the CAD wedge in place
to the east of the Appalachians will strengthen. Large scale
forcing for ascent will also gradually increase from west to
east tonight into tomorrow as a shortwave trough and embedded
upper low approach from the Ohio Valley. As large scale forcing
for ascent increases, the relatively low coverage of showers
today will increase substantially heading into tonight, and
persist through tomorrow, tomorrow night, and Wednesday morning.
At times the precipitation may even resemble more of a
continuous stratiform rain shield as opposed to showers.

The flow pattern across the CONUS over the next couple days will
be extremely complex, with a split flow pattern and a closed
upper level ridge building to the north of the upper low over
the Ohio Valley. So while the big picture of the forecast
tonight through Wednesday has high confidence (low clouds,
cool, and rainy), there is still some forecast uncertainty
regarding the finer scale details. A few model solutions attempt
to produce several inches of rainfall over localized areas as
we become positioned in the right entrance region of a strong
jet streak developing off to our north and east, but there is
lots of model to model inconsistency as to if that will occur
and where. As of now, the most likely scenario appears to be for
most of the region to receive 1-2 inches of rainfall spread out
a prolonged period time period tonight through Wednesday
morning. If this were to occur, the rainfall would be beneficial
in nature given the ongoing drought conditions. However, if the
solutions that produce isolated totals of 3-6 inches were to
play out, there could be localized issues with flooding. Even if
the solution with higher end totals plays out, instantaneous
rainfall rates won`t be overly high given the lack of
instability, so it would be more of a prolonged soaking
rainfall leading to areal flooding, as opposed to thunderstorms
producing flash flooding. We`ll continue to monitor this
potential as we move forward.

Either way, Tuesday and Wednesday will feature low clouds,
gusty northeasterly winds, and well below normal temperatures.
Temperatures likely hold in the 60s on Tuesday, and may even
struggle to get out of the 50s on Wednesday as the CAD wedge
reaches its peak strength.

KEY MESSAGE 2...Daily shower chances, abundant cloud cover, and cool
temperatures continue through Thursday. Drier this weekend.

A persistent wedge-like pattern will remain through at least
Thursday as wedging/blocking high pressure remains up across eastern
Canada and coastal low pressure strengthens off the Mid-Atlantic
coast. This will lead to persistent onshore flow as a series of
shortwave disturbances pivot around the coastal low offshore and the
remnant stalled frontal boundary south/east of the region. The
persistent northeast/east fetch off the Atlantic will yield
continued cloudiness, minor to (potentially moderate) coastal
flooding (along the western shore of the Chesapeake Bay), cool
temperatures, and widespread shower chances to the region.

With a persistent wedge in place expect highs to struggle to get out
of the upper 50s and mid 60s through at least Friday. Overnight lows
will fall into the 40s and 50s given the cool maritime airmass
overhead.

Coastal low pressure will track northward toward the NJ/Long Island
coast Friday into Saturday putting more subsidence over the region.
This will allow for decreasing precipitation chances and rising
temperatures with highs in the upper 60s and mid 70s. Even with that
said, model discrepancies remain beyond Saturday as the coastal low
looks to retrograde in the vicinity of the Mid-Atlantic coast.
Current 00z members have the low meandering up toward the Jersey
Shore Saturday before dropping is back south toward the Delmarva
Sunday into the early part of next week. This would lead to abundant
cloud cover in place along with continued chances for showers
,especially in locations east of the Blue Ridge/closest to the low
pressure system. It`s not until the middle of next week (i.e
September 30th) when the pattern looks to flip again as a stronger
front looks to cross the region. Temperatures will remain near
normal through the remainder of the extended period with above
normal precipitation expected.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
A challenging ceiling forecast today. MVFR ceilings have
streamed in from the north behind a cold front and are slowly
making southward progress early this morning. There are
conflicting signals regarding whether ceilings will lift back up
to VFR near peak heating today. Locations further north and east
should have the greatest chance of returning back to VFR for a
few hours this afternoon. For now, that is in the TAF at BWI and
MTN, but it can`t be ruled out at DCA or IAD as well. For now
have maintained continued MVFR conditions at those sites.
Showers may be possible on and off through the day. The greater
the coverage of those showers, the lesser the likelihood that
conditions return back to VFR. Winds today will generally be out
of the north to northeast at around 5-10 knots.

Guidance is in better agreement that ceilings will lower to IFR
tonight as showers increase in coverage across the area. IFR
ceilings and on and off showers then continue through the day
Wednesday. Winds will be out of the northeast tonight through
Wednesday, and should gust to around 15-25 knots on Tuesday and
Wednesday.

Sub-VFR conditions look to continue at times through at least Friday
as shower chances persists due to coastal low pressure offshore.
Conditions look to slowly improve Friday afternoon and night as
coastal low pressure lifts north of the region. VFR conditions
should prevail through the weekend although intermittent periods of
sub-vfr remain possible Sunday into early next week for terminals
mainly along and east of I-95 as coastal low pressure remains
nearby. Increase north to northeasterly flow is expected through
Friday. Gusts of 15 to 25 kts are possible, especially at terminals
near the waters.

&&

.MARINE...
Small Craft Advisories remain in effect in the main stem of the
Bay through noon within northerly flow. There will likely be a
small lull in the winds this afternoon, before they pick up
again in earnest within northeasterly flow later tonight into
tomorrow as high pressure strengthens to our north. A prolonged
period of northeasterly winds is expected through Wednesday with
that area of high pressure in place. Small Craft Advisories
have been issued again starting tonight and continuing through
Tuesday night. At least high-end Small Craft Advisory gusts will
continue within northeasterly flow through at least Wednesday.
Low- end Gale gusts can`t be ruled out late Tuesday night into
Wednesday across the widest waters of the Bay, but confidence in
that occurring was too low for Gale Watches at the moment.

High end small craft conditions will continue through Friday due to
increased onshore north to northeasterly flow. Expect gusts between
20-25 kts with 30 kt gusts sporadically sprinkled over the middle
and open waters. On and off showers are also possible at times as
multiple shortwave disturbances pivot through. SCA conditions will
likely continue through the weekend as low pressure remains off the
Mid-Atalntic coast. Strongest gusts will be over the bay and lower
tidal Potomac.

&&

.TIDES/COASTAL FLOODING...
A cold front will pass south of the waters today. North to
northeasterly flow will lead to decreasing anomalies today, with
no coastal flooding anticipated. That will be short-lived,
however, as tides are expected to snap back to the north, with
anomalies rapidly rising again later tonight through the day
tomorrow. Elevated tide levels are then expected through much
of the week as a strong area of high pressure builds to our
north, leading to persistent onshore flow. The wind direction
will be closer to northeasterly rather than easterly, so the
tidal levels are expected to increase with southward extent in
the Bay. Many locations will likely reach Minor Flood Stage on
Tuesday and Wednesday, and Annapolis could come close to
flooding tonight as well. Moderate flooding can`t be ruled out
at some locations, but appears to be a less likely outcome at
this juncture. A coastal low is expected to develop offshore
later this week, potentially prolonging coastal flood concerns.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory from 8 PM this evening to 6 AM EDT
     Wednesday for MDZ008.
     Coastal Flood Advisory until 6 AM EDT early this morning for
     MDZ014.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 8 PM this evening to 6 AM EDT
     Wednesday for ANZ530>534-537>543.
     Small Craft Advisory until noon EDT today for ANZ531>533-
     539>541.
     Small Craft Advisory from 6 AM this morning to noon EDT today
     for ANZ534-543.
     Small Craft Advisory from 6 AM Tuesday to 6 AM EDT Wednesday
     for ANZ535-536.

&&

$$

DISCUSSION...KJP/EST
AVIATION...KJP/EST
MARINE...KJP/EST