038
FXUS61 KLWX 220124
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
924 PM EDT Thu Aug 21 2025

.SYNOPSIS...
A meandering stalled frontal boundary will continue south of the
area later today while Hurricane Erin moves further offshore from
Mid-Atlantic coast. Weak high pressure will build in from the
north Friday into Saturday. Dry conditions continue through
Saturday with another cold front set to cross Sunday into
Monday. A strong dome of Canadian high pressure builds
thereafter for much of next week.

&&

.NEAR TERM /UNTIL 7 AM FRIDAY MORNING/...
The 00Z KIAD sounding shows dry air moving into the region with
mid level RH values of 60% compared to 85% observed on the 12Z
sounding this morning. Cloud cover as overall decreased,
although clouds will linger overnight. No changes were made to
the forecast with the previous forecast discussion below.

Continuing to monitor the progression of a meandering frontal
boundary south and east of the area this afternoon. This boundary
remains draped over the southern Delmarva back across the central VA
Piedmont/southern Shenandoah Valley and into far southern WV. The
boundary will continue further south and east this evening as
Hurricane Erin moves further off into the western Atlantic and weak
high pressure builds in from the Great Lakes/Ohio River Valley.
Until this happens, expect a repeat of what we saw yesterday
across the region with ample overcast low to mid stratus),
pockets of light drizzle and fog, and cool temperatures due in
part to stout onshore flow. Reductions in visibility are
possible given the overall pattern especially toward foothills
of the Blue Ridge and Catoctins as well as back across the
Alleghenies with lower ceilings in place. These conditions will
likely hold strong through mid-afternoon with slow improvements
this evening due in part to a lack of solar insolation as well
as dry air advection pushing into the region.

As for Hurricane Erin, expect further acceleration to the north and
east today as it pulls further away from the Mid-Atlantic coast and
toward the eastern Canadian Maritimes. A continuation of coastal
flooding concerns along the western shore of the Chesapeake Bay and
up across the tidal Potomac will remain over the next few high tide
cycles. For those traveling to the Delmarva beaches, be aware of
continued tidal flooding and rip current concerns which will likely
last through the weekend.

With the front and upper trough nearby and Hurricane Erin just
offshore expect a tightened pressure gradient across the area this
afternoon and evening. This will lead to a bump in the overall
synoptic wind field across the entirety of the area (especially
along and east of I-95) this afternoon into early evening. Winds
will generally be out of the north and northeast with gusts hovering
between 20-25 mph. Locally higher gusts are possible over far
southern MD and the northern neck of VA as well as adjacent open
waters of the lower Chesapeake Bay (see Marine section).With some
residual moisture and weak lift (departing front/upper trough)
overhead, isolated to widely scattered showers may pop up. Like
earlier this morning, any such shower activity would track toward
the southwest (mainly across the central VA Piedmont, western shore
of the bay, and southern MD). A couple rumbles of thunder cannot be
ruled out in Nelson, Highland, and Augusta counties given closer
proximity to the front. Any convective threats wind down by around 6-
8 PM.

Ample overcast and stout north/northeasterly flow will hold
temperatures back into the low to mid 70s today with mid to upper
60s across the mountains. Relative to mid/late August climatology,
this forecast is around 8 to 12 degrees below average. Wind fields
weaken tonight with gradually clearing skies as ample dry air
advection funnels in. Clouds will hang on the longest west of US-
15/the Blue Ridge. Some fog is possible especially in the river
valleys although confidence in widespread fog is low especially west
of the metros given the residual cloud cover. Low temperatures are
forecast to be in the upper 50s to mid 60s.

&&

.SHORT TERM /7 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
Sunshine returns Friday as weak high pressure builds in from the
Ohio River Valley and Great Lakes region. North to northeast flow
will continue as Hurricane Erin pushes further offshore. This will
lead to a notable drop in dewpoints (i.e humidity) with values in
the mid 50s and low 60s. More typical of what you would see in early
Fall or Spring behind a strong cold frontal boundary. Outside of the
drop in dewpoints and mostly sunny skies expect winds to lighten as
the pressure gradient relaxes with the departing trough/tropical
cyclone pushing well offshore. High temperatures Friday will range
from the upper 70s to low 80s in most areas with mountain
locations above 3000 feet hovering in the mid to upper 60s.
Expect a decent radiational cooling setup Friday night with
clear skies and light winds. This will result in low
temperatures in the upper 50s and low 60s across much of the
region outside of the immediate Washington DC/Baltimore metro
centers. Some sheltered river valley locations especially west
of the Blue Ridge could dip as low as the upper 40s and low to
mid 50s.


Weak high pressure will shift east of the area Saturday as a strong
upper level trough and cold front approach the region for the back
half of the weekend. Humidity will increase as a result of southerly
return flow with high pressure pushing offshore. In addition, a
few showers and thunderstorms cannot be ruled out west of the
Blue Ridge and toward the Alleghenies Saturday afternoon given
the proximity to the approaching trough/frontal boundary.
Overall forcing appears to be lacking with CIPS, CSU, and even
SPC hinting at areas mainly along and west of the Alleghenies
for any severe threat late into the weekend into early next
week. Storms will mostly be driven by the terrain Saturday
afternoon and evening with limited to no spread east of I-81.
Highs Saturday will push back into the upper 70s and low 80s.
Lows Saturday night will fall back into the mid to upper 60s
with upper 50s and low 60s west of the Blue Ridge, More
widespread rain chances look to hold off til Sunday.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
An upper low over southern Ontario on Sunday will dig across the
Great Lks and northern mid-Atlantic early next week pushing a
strong cold front through the area late Sunday night. Showers
and thunderstorms, possibly severe, are expected Sunday into
Sunday night before cdfnt exits offshore Monday.

Series of shortwave-troughs will traverse the region next week
reinforcing the longwave trough pattern across the East. At the
surface, Canadian high pressure will dominate much of next week
keeping generally dry and cool conditions. Nighttime lows will
be considerable cooler than climatology for late Aug with lows
in the 50s.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
The stalled frontal boundary that has plagued the weather forecast
the last few days continues to work further south and east of the
area this afternoon. Overall, it`s a mash up of MVFR cigs with
intermittent pockets of IFR scattered mainly east of the Blue Ridge
where pockets of drizzle and fine light rain remain. Expect slow
improvements later this afternoon and evening as onshore winds
switch to the north dragging more dry air advection in the region.
Generally speaking, expect MVFR conditions at most terminals
with a return to VFR later this evening into late tonight. Some
patchy fog is possible overnight especially in the deeper river
valleys and east of the Blue Ridge as skies clear. Further west
of MRB and SHD, fog development may not be as pronounced given
lingering cloud cover.

Winds will remain elevated out of the north/northeast this afternoon
due in part to the tightened gradient between departing Hurricane
Erin over the western Atlantic and the stalled front/upper tough
nearby. Expect gusts of 20-25 kts this afternoon with gusts up to
30kts at terminals near the water. Winds will gradually decrease
tonight into Friday while remaining out the north. VFR conditions
are expected Friday as high pressure builds into the region. This
will lead to decreasing winds out of the north at 5-10 kts. VFR
conditions will likely continue into Saturday as high pressure
pushes east of the region. COnvective chances due return for
terminals mainly west of MRB and SHD Saturday afternoon and evening
as another front/trough approach the region. Winds will turn back to
the south gusting between 10-15 kts. Additional showers are possible
for areas east of the MRB Saturday night although confidence is low.

Prevailing VFR conditions are expected on Sunday and Monday,
although temporary drops to sub-VFR may be possible on Sunday as
scattered thunderstorms move through. Winds will be out of the south
on Sunday, and then out of the west to northwest on Monday. VFR
conditions are expected thereafter for much of next week as Canadian
high pressure settles over the region.

Showers and thunderstorms are likely Sun-Sun night along a cold
front before it exits offshore Monday morning.

&&

.MARINE...
A Coastal Flood Watch is in effect for Anne Arundel County, Maryland
late tonight through Saturday morning. Two to two and half feet of
inundation above ground is expected especially around high tide
Friday evening and again Saturday morning.

Tidal anomalies will remain elevated for the next 24 hours as
onshore flow strengthens in response to Hurricane Erin tracking
further offshore into the western Atlantic.

As winds slacken Friday night into Saturday, a snap-back event is
expected to occur raising water levels further. Moderate coastal
flooding is likely at Annapolis and widespread minor coastal
flooding elsewhere (i.e DC Waterfront. ALexandria, Baltimore, and
Havre de Grace). Water levels likely remain elevated until the cold
frontal passage that comes in early Monday.

SCA conditions will likely continue for all waters through this
evening with occasional gale force conditions over the open waters
of the bay. North to northeasterly winds will gusts between 20 to 25
kts with gusts of 30 to 35 kts possible from Cove Point south to
Tangier Island. Winds will remain elevated through late tonight into
Friday morning. Small Craft Advisories have been expanded to
encompass this threat. Additional SCA conditions may linger over the
open waters of the bay and tidal Potomac through midday Friday.
Winds should slacken for the entirety of the bay/tidal Potomac
as weak high pressure builds in from the north and settles over
the region. Winds will remain out of the north at less than 15
kts. The high eventually weakens further while shifting offshore
Saturday. This will allow the winds to switch back to the south
and for channeling to occur. Southerly winds will gusts to
around 15 to 20 kts Saturday afternoon. This may lead to a
period of SCA conditions over the middle and lower waters
Saturday afternoon and evening.

Sub-SCA level winds are expected on both Sunday and Monday. Winds
will be out of the south on Sunday, and then out of the west to
northwest on Monday. SMWs may potentially be needed as thunderstorms
pass over the waters Sunday afternoon into Sunday evening.

SCA conditions are possible Sunday afternoon and night in pre-
frontal environment and again late Monday night through much of
next week in a post-frontal environment.

&&

.TIDES/COASTAL FLOODING...
A Coastal Flood Watch is in effect for Anne Arundel County, Maryland
late tonight through Saturday morning. Two to two and half feet of
inundation above ground is expected especially around high tide
Friday evening and again Saturday morning.

Tidal anomalies will remain elevated for the next 24 hours as
onshore flow strengthens in response to Hurricane Erin tracking
further offshore into the western Atlantic.

As winds slacken Friday night into Saturday, a snap-back event is
expected to occur raising water levels further. Moderate coastal
flooding is likely at Annapolis and widespread minor coastal
flooding elsewhere (i.e DC Waterfront. ALexandria, Baltimore, and
Havre de Grace). Water levels likely remain elevated until the cold
frontal passage that comes in early Monday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 3 AM EDT Friday for MDZ008.
     Coastal Flood Advisory from 2 AM Friday to 2 AM EDT Saturday
     for MDZ014.
     Coastal Flood Watch from late Friday night through Saturday
     morning for MDZ014.
     Coastal Flood Advisory from 1 AM Friday to 7 AM EDT Sunday for
     MDZ016.
     Coastal Flood Advisory until 7 AM EDT Sunday for MDZ018.
VA...Coastal Flood Advisory from 1 AM Friday to 7 AM EDT Sunday for
     VAZ057.
WV...None.
MARINE...Small Craft Advisory until 3 AM EDT Friday for ANZ530>533-
     538>542.
     Small Craft Advisory until 6 AM EDT Friday for ANZ534-537-543.

&&

$$

SYNOPSIS...EST
NEAR TERM...AVS/EST
SHORT TERM...EST
LONG TERM...LFR
AVIATION...LFR/EST
MARINE...LFR/EST
TIDES/COASTAL FLOODING...