271
FXUS61 KLWX 180801
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
401 AM EDT Mon Aug 18 2025

.SYNOPSIS...
A cold front will clear the entire area this morning before
stalling near the Virginia/North Carolina border. This system
remains south of the region thruogh mid-week before the boundary
pushes farther south toward the southeastern U.S. coast by
Thursday. High pressure will then return from the north through
at least Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
The early morning surface analysis places a slow moving cold
front from southern New Jersey down across southern Maryland
into eastern Kentucky. Any related convection has raced well
ahead of this boundary as showers persist over southeastern
Virginia. Along and behind the cold front, the GOES-19
microphysics RGB imagery show an uptick in low/mid cloud
development. This thickening cloud deck should generally offset
more widespread fog formation. Any significant drop in
visibility appears to be limited in time based on multi-hour
observations at K2G4 and KCHO.

A nearly saturated boundary layer is observed across much of the
region as relative humidity values range from 85 to 100 percent.
Current temperatures are in the upper 60s to mid 70s, with dew
points in the upper 60s to low 70s. As the mentioned cold front
continues to drop southward through the day, below average
temperatures will ensue for the days ahead. Post-frontal winds
become more northeasterly today which aids in the mentioned
cool down. The overall theta-e gradient tightens over time
(325-330K in the cool sector and 345-350K to the south) which
helps augment synoptic wind fields. Expect northeasterlies to be
become breezy at times, generally averaging around 15 to 20 mph.
These gusts should weaken in the evening/overnight period.

After spending the past several days with near to above average
temperatures, today will feel like quite the contrast. Forecast
highs are expected to reach the mid 70s to low 80s, with mid 60s
to mid 70s across mountain locations. The persistent
northeasterly onshore flow will maintain extensive low clouds
over the area. The pattern aloft does not really carry any
identificable shortwave or mesocale feature. As such, any
showers that do develop are likely be to driven by the enhanced
onshore flow and accompanying sea/river/bay breezes. The degree
of stability of the atmosphere should also favor weaker vertical
motions and thus lighter shower activity. At this juncture, the
best chance for any such showers would be east of the Blue
Ridge. An isolated thunderstorm cannot be ruled out over far
southern Maryland given closer proximity to the front.

By tonight, the mentioned frontal zone is forecast to be near
the Virginia/North Carolina border. To the north of this
boundary, a steady east to northeasterly wind continues which
maintains a maritime influence on the sensible weather. A
thickening stratus deck is expected into the night with some
patchy fog possible in spots. Depending on the depth of
saturation, some areas of drizzle or mist are certainly not out
of the question either. Overnight lows fall into the 60s with
spotty upper 50s across the mountain ridgetops.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
On Tuesday, a broad 594 dm ridge persists across the Four
Corners up along the Rockies. Meanwhile, downstream heights
decrease slightly, generally on the order of 590 dm down to 588
dm. These subtle height falls should help invigorate slightly
more organized lift north of the stalled front. Thus, expect
isolated to widely scattered showers to develop during the core
heating hours on Tuesday. However, conditions remain fairly
stable as east-northeasterly flow continues. Forecast high
temperatures rise into the mid 70s which is around 8 to 12
degrees below mid-August climatology. Ensemble box-and-whisker
plots do show a bit more spread which suggests there is some
room for slightly warmer temperatures. A few lingering showers
are possible into Tuesday night, coupled with continued low
clouds and lows in the 60s.

By Wednesday, Hurricane Erin is forecast to be lifting northward
around halfway between the Carolinas and Bermuda. It is at this
point, a continued northeastward recurvature is likely. Any
local effects would come with a gradual increase in synoptic
wind fields, particularly over the waterways. Shower chances do
increase, but in response to an approaching surface low/wave
along this wavy frontal zone. This introduces a 30 to 50 percent
chance for showers and thunderstorms, especially west of U.S.
15. High temperatures return to the low 80s along with
seasonably humid conditions. Most opportunities for showers wind
down overnight with lows in the 60s (low 70s in D.C. and
Baltimore).

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As a shortwave trough moves well east of the area, this allows
Hurricane Erin to follow suit and start to move well offshore on
Thursday. Our area remains in northwesterly flow aloft and a
relatively weak surface pattern through Friday. Light winds and near
to slightly below normal temperatures are expected during that time,
with highs in the low to mid 80s and lows in the 60s. Most locations
should stay dry, though a few afternoon shower or thunderstorm are
possible, especially to the west of the Blue Ridge.

High pressure moves offshore of southern New England by Saturday.
Southerly flow around the high will lead to an increase in low-level
moisture as dewpoints climb back through the 60s, and potentially
even approaching 70 degrees. Meanwhile, a deep upper trough starts
to dig southeastward across the Great Lakes. Winds aloft increase
locally in response to that feature. As large scale ascent ahead of
that trough starts to overspread the area, showers and thunderstorms
may be possible by Saturday afternoon, and again Sunday afternoon.
Some of these storms could potentially be on the stronger side, as
surface based instability overlaps with increasing flow aloft.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
A cold front is continuing its southward progression across the
area. While any shower chances have ended, the post-frontal air
mass is characterized by a greater Atlantic influence. Areas of
low/mid clouds continue to thicken with MVFR ceilings expected,
particularly across the D.C. and Baltimore terminals. These
largely stick around throughout the day given northeasterly
winds which may gust up to 20 knots at this times this
afternoon. Spotty light showers cannot be ruled out, but expect
much of the day to be dry. A marine layer persists into tonight
with continued MVFR ceilings, perhaps dropping to IFR in spots.

Additional sub-VFR ceilings are looking possible again on
Tuesday given little change in the pattern. Stratus clouds
should be plentiful in the continued east-northeasterly flow
regime. A few more showers are possible, but these should be
more or less scattered in nature. The frontal zone remains well
to the south near the Virginia/North Carolina border. As a wave
of low pressure rides along the front, a better chance for
showers comes on Wednesday, especially for the western most
terminals.

VFR conditions are likely to prevail at the end of this week as
Hurricane Erin quickly moves well offshore. Breezy northeast winds
possible Thursday, then winds diminish quickly Thursday night.
Cannot rule out some lower clouds at each night to morning that
bring periods of MVFR conditions to the I-95 terminals.

&&

.MARINE...
A cold front has nearly cleared the entire waterways. This
frontal system eventually settles near the Virginia/North
Carolina through mid-week. In the wake of this frontal passage,
an uptick in northerly winds is likely as channeling effects
ensue. Small Craft Advisories go into effect for much of the day
with gusts up to 20 knots, locally up to 25 knots over wider
portions fo the Chesapeake Bay. Winds may remain slightly
elevated over the southern most portions of the Chesapeake Bay.
Thus, such advisories may get extended into the first half of
Tuesday.

For the second half of Tuesday into Wednesday, easterly winds
should remain below Small Craft Advisory thresholds. Eventually
the influence of the broad wind field of Hurricane Erin come
into play late Wednesday. Additional advisories are likely at
this point as north-northeasterly winds strengthen.

SCA conditions are likely to continue Thursday into Thursday night
as Hurricane Erin pushes further offshore. The strongest winds will
be over the Chesapeake Bay. Winds diminish Friday when high pressure
starts to build in from the north.

&&

.TIDES/COASTAL FLOODING...
Elevated tidal anomalies persist through tonight. Annapolis is
forecast to reach minor flood again during high tide early this
morning. While other locations aren`t currently forecast to
flood, some could come close (ie, Alexandria, Havre de Grace,
Solomons, and Dahlgren). A passing cold front should reduce
water levels slightly heading into tonight. However, prolonged
onshore flow will likely result in additional (possibly more
widespread) tidal flooding late Tuesday into Wednesday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory from 6 AM this morning to 2 AM EDT
     Tuesday for MDZ008.
     Coastal Flood Advisory until 5 AM EDT early this morning for
     MDZ014.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 6 AM this morning to 2 AM EDT
     Tuesday for ANZ530>533-539>541.
     Small Craft Advisory from noon today to 6 AM EDT Tuesday for
     ANZ534-537-543.
     Small Craft Advisory from 6 AM this morning to 6 PM EDT this
     evening for ANZ535-536-538-542.

&&

$$

SYNOPSIS...BRO
NEAR TERM...BRO
SHORT TERM...BRO
LONG TERM...KRR
AVIATION...BRO/KRR
MARINE...BRO/KRR
TIDES/COASTAL FLOODING...LWX