808
FXUS61 KLWX 162344
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
744 PM EDT Sat Aug 16 2025

.SYNOPSIS...
Weak high pressure will remain wedged against the eastern face of
the Appalachians through this evening before gradually eroding
Sunday into the start of the new workweek. A cold front will
approach from the Great Lakes and Ohio River Valley late Sunday
night into Monday before stalling over the area midweek. This front
will bring increased shower and thunderstorm chances along with
cooler temperatures to the region. The stalled front will push south
and east of the area Thursday with Canadian high pressure returning
from the north late week into the weekend.

&&

.NEAR TERM /THROUGH SUNDAY/...
Any residual shower and thunderstorm activity should quickly come to
an end with the loss of daytime heating (fading before 10pm). A pop
up shower cannot be ruled out along and west of the Blue Ridge,
given the low level convergence zone that remains between the
Alleghenies and Catoctins/Blue Ridge mountains. Overall most will
remain dry with mostly clear to partly cloudy skies as shortwave
energy kicks east. Winds will remain light and variable turning from
the east and southeast to the south and southwest late tonight into
Sunday morning.

The light winds combined with clearing skies should set us up for
another round of mountain/river valley fog, especially west of the
Blue Ridge. Expect fog to develop in these areas between 2-5am
Sunday morning, with local visibilities as low as a quarter mile.
Overall coverage will be patchy in nature and mainly in areas that
are near bodies of water or that did see rain today. Overnight lows
will range from the mid 60s to mid 70s. Lows in the low 60s are
possible in the sheltered high valleys and high elevations of the
Alleghenies.

Weak high pressure remains wedged along the eastern face of the
Appalachians through Sunday morning although it will shift eastward
throughout the day. Onshore flow will cease with winds switching to
more of the southerly and westerly direction. Meanwhile, a trough of
low pressure will likely develop on the lee side of the
Appalachians Sunday afternoon. This trough combined with an
incoming cold front frontal boundary from the Great Lakes and
Ohio River Valley will act as focal points for scattered shower
and thunderstorm development. Highest confidence for
thunderstorm development appears to be in the northern and
western parts of the forecast area Sunday afternoon given the
proximity to the aforementioned surface features above. There is
still some uncertainty with how far southeast storms make it
before loss of daytime heating causes a weakening trend. It`s
possible future forecasts may need to increase PoPs a bit into
the metro areas. SPC has introduced a marginal risk for
potential wind damage with multicell clusters, but the overall
CAPE, shear, and DCAPE parameter space are not suggestive of a
notable severe weather threat. The storms should be somewhat
progressive, but locally heavy rain could occur as precipitable
water maximizes ahead of the front.

High temperatures Sunday will climb into the low to mid 90s east of
the mountains given the loss of onshore flow. Dew points may also
mix down into the upper 60s and low 70s given the drier air aloft
and some downsloping off the mountains. Even with that said, heat
indices will range between 95 to 100 degrees especially along and
east of I-81. Lows Sunday night will fall back into the upper 60s
and low to mid 70s with areas of mountain/river valley fog.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
Uncertainty increases into Monday with guidance differing on frontal
position (overhead or pushing south of the area) and what kind of
forcing could exist along the boundary that may aid in the
generation of more showers and thunderstorms. The current NBM
forecast may end up too conservative (in clouds and PoPs), as there
are indications at least portions of the area may end up rather
cloudy and showery through the day. Regardless, temperatures do take
a downward trend. Most areas will top out in the 80s, though some
places could stay in the 70s. With the frontal zone potentially
still nearby and an increasing marine influence on northeast winds,
some rain showers could continue into Monday night.

Upper level ridging will build over the central CONUS as upper level
troughing digs across Quebec through mid week. At the surface, a
stalled front will remain overhead yielding daily shower and
thunderstorm chances. Temperatures will cool slightly with high
temperatures in the low 80s Tuesday. Higher elevations will remain
in the 60s to low 70s.


&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Upper ridging will build over the Rockies early next week, which
will cause flow aloft downstream to turn northwesterly. At the
surface, high pressure is expected to remain in place off the New
England coastline. The combination of northwesterly flow aloft and
high pressure to our northeast at the surface should result in low
coverage of afternoon thunderstorms and near to slightly below
normal temperatures throughout the long term period. The best chance
for storms currently looks to be on Wednesday as a disturbance aloft
descends down in northwesterly flow from the Great Lakes.
Temperatures will run near to slightly below normal, with highs in
low to mid 80s and lows in the 60s to near 70.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
A few isolated showers and perhaps a t-storm may linger in the
vicinity of KCHO and KSHD through at least 01z/9pm. Expect
temporary reductions under these showers otherwise VFR
conditions should prevail at most if not all the terminals
through the valid TAF period. Once spotty shower/t-storm
activity diminishes expect mostly clear to patchy cloudy skies
overnight. Winds will remain light out of the south and
southeast before eventually turning calm early Sunday morning.
This will lead to another round of patchy fog development in and
around KCHO and KMRB. Expect vsbys to drop in these areas as
well as at other river valley terminals west of the Blue Ridge
between 06-09z/2-5am. Any fog should mix out by 14z/10am Sunday
morning.

Most of Sunday remains dry with VFR conditions and light south to
west winds as a surface trough develops. Scattered thunderstorms
will approach from the northwest during the afternoon ahead of a
cold front. MRB has the highest chance of seeing a storm, but a few
storms could hold together into the metro areas toward evening.

Low ceilings may develop if the front pushes south of the area
Sunday night. The frontal position remains uncertain into Monday.
Thunderstorms will be possible south of the front (highest chance at
CHO), while low clouds and showers are possible to the north.

Sub-VFR ceilings appear possible within east to southeasterly low-
level flow early Tuesday morning, and then again late Tuesday night
into early Wednesday morning.

&&

.MARINE...
Sub-SCA level winds are expected to continue through Sunday. Any
spotty shower or t-storm activity should remain with the bay breeze
along the eastern shore through at least 01z/9pm. Light winds out of
the southeast look to switch to the south tonight at less than 15
kts.

A broken line of showers and thunderstorms are possible as a cold
front approaches Sunday evening, some of which could have gusty
winds. Ahead of these storms, southerly channeling may approach
advisory levels on the middle bay. By Monday, post-frontal
northeasterly flow ensues with gusts around 10 to 15 knots, perhaps
approaching advisory criteria by late in the day. If the front
doesn`t push far enough south, however, thunderstorms could develop
again Monday afternoon.

Sub-SCA level east to southeasterly winds are expected on Tuesday
and Wednesday. However, winds may increase some during the middle of
the week as gradients tighten with Erin offshore.

&&

.TIDES/COASTAL FLOODING...
Elevated tidal anomalies continue through the remainder of the
weekend with some uptick forecast due to onshore winds. Annapolis is
forecast to reach minor flood tonight and Sunday night during high
tide. While other locations aren`t currently forecast to flood, some
could come close, especially Sunday evening (i,e Havre de Grace,
Solomons, and Dahlgren). A passing cold front should reduce water
levels slightly heading into Monday and Tuesday.


&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory until 4 AM EDT Sunday for MDZ014.
VA...None.
WV...None.
MARINE...None.

&&

$$

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