900
FXUS61 KLWX 060034
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
834 PM EDT Sat Jul 5 2025

.SYNOPSIS...
High pressure will move off the Mid Atlantic coast through
Sunday while low pressure associated with Tropical Storm Chantal
tracks toward the Carolina coast. A cold front will approach
from the northwest Monday, before potentially stalling near the
area during the middle to latter portions of next week.

&&

.NEAR TERM /UNTIL 7 AM SUNDAY MORNING/...
No changes to the forecast as dry and mild conditions continue
overnight. The 00Z KIAD sounding shows plenty of dry air in the
mid-levels leading to mostly clear skies across the area outside
of a few high level clouds. Previous forecast discussion below:

Tranquil weather continues during this holiday weekend. The
local area remains in between a pair of primary synoptic
features aloft. A deep upper trough has moved into the Canadian
Maritimes while broad ridging extends from the Ozarks up into
the Tennessee/Ohio valleys. The upstream ridge will continue to
migrate eastward in time which supports a slow but steady
warming trend. Early afternoon temperatures are already well
into the 80s, accompanied by dew points in the upper 50s to mid
60s. Compared to yesterday at this time, these dew points are
around 5 to 10 degrees higher. Despite the increase in humidity,
subsidence aloft has generally squashed any vertical development
of clouds. GOES-19 visible satellite imagery just shows a broad
area of shallow cumulus development, some of which are locally
enhanced along the terrain where lift is a bit more pronounced.

A dry forecast continues through the remainder of the day with
high temperatures reaching the 90 degree mark in a few spots.
Quiet conditions persist into the evening and overnight hours.
For early July standards, tonight`s conditions are on the cool
side as many see low temperatures in the low/mid 60s (upper 60s
inside D.C. and Baltimore). Even some upper 50s are possible
across the central Shenandoah Valley back into the Potomac
Highlands. Patchy fog may develop over these locations,
particularly in areas typically more prone for radiation fog.

&&

.SHORT TERM /7 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
As is common in the summer months, large-scale gradients remain
weak across the country. The pattern ahead to finish the weekend
and into early next week will certainly be comprised of such a
regime. Above average mid/upper level heights persist over a
vast corridor of the eastern U.S., generally running between
588-591 dm. At the same time, a slow moving upper low will
retrograde westward across the Gulf of America.

At the surface, the key feature of interest is the remains of
what is currently Tropical Storm Chantal. The latest forecast
package from the National Hurricane Center shows this tropical
circulation approaching the upper South Carolina coast by Sunday
morning. Eventually what remains lifts toward the north and
east into central/eastern North Carolina early Monday morning.
While the actual system will likely have dissipated by Monday,
the uncertainty lies around where the tropical moisture ends up.
All indications are an elevated area of 2 inch plus
precipitable water values moves into some portion of the Mid-
Atlantic region by early next week. However, uncertainty still
remains high as the system is still offshore of the South
Carolina coast.

As this tropical moisture lingers somewhere near the region, a
slow moving cold front will approach from the west on Monday.
During the morning hours, the frontal system is forecast to be
situated over interior portions of New England back across the
northern Ohio Valley. As the boundary approaches from the west,
it may tap into this moisture-rich environment. While frontal
boundary interactions with tropical moisture plumes can be heavy
rain producers, a lot of details are not clear at this point.

The overall temperature forecast will feature seasonably warm
conditions with highs pushing into the upper 80s to low 90s on
Sunday. Early morning radiation fog across the Potomac Highlands
and Shenandoah Valley should quick burn off an hour or so after
sunrise on Sunday. This should lead to a mostly sunny start to
the day before high clouds increase from south to north ahead of
Chantal. As this occurs, some of the leading edge of showers
may impact areas south of I-66 during the second half of Sunday.
Total amounts closer to the I-64 corridor could approach 0.25 to
0.50 inches, with lighter amounts off to the north. Residual
shower chances persist into the overnight hours for spots east
of the Shenandoah Valley. Mild conditions remain into the night
with lows in the upper 60s to mid 70s (low/mid 60s in the
mountains).

As mentioned earlier on, an increasingly stormier pattern
evolves into the work week ahead. The slow moving cold front and
increasing tropical moisture will make for a challenging
forecast. As this stands, a summertime air mass remains in place
with seasonable temperatures and abundant humidity. The guidance
has trended slightly cooler over the last few days given the
influence of clouds and increasing storm chances. Most should
see highs in the mid/upper 80s, with perhaps a pocket of low 90s
across the Shenandoah Valley and the Allegheny mountain valleys.
Meanwhile, mountain locales can expect temperatures in the mid
70s to low 80s. Afternoon thunderstorm chances have increased to
around 40 to 60 percent before tapering off into the night. A
mild/humid air mass continues into Monday night with lows in the
upper 60s to mid 70s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Tuesday through the end of the week will be quite active as several
pieces of shortwave energy move across the region amidst a
stalled/slow-moging frontal boundary. Hot and humid conditions
paired with all of these upper-level systems will likely result in
several rounds of thunderstorms. Still thinking that Thursday is
going to be the day with the highest threat for more organized
severe thunderstorms based on the latest model guidance. This looks
to be the strongest system, so would look to this day as a day to
watch. Otherwise, there will be daily chances for isolated to
scattered strong/severe thunderstorms areawide.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
Mainly VFR conditions are expected at the area terminals through
the holiday weekend. The one exception could be radiation fog
that develops late tonight which may impact KCHO and KMRB.
Forecast visibility may teeter between VFR and MVFR at times
during the overnight hours. Light southerly winds persist
through the weekend as gradients remain rather weak.

For the second half of Sunday, high clouds will be on the
increase as they spread from south to north ahead of the
remnants of Tropical Storm Chantal. Some showers are possible,
especially across more southern terminals (i.e., KCHO).
Restrictions would be possible down in KCHO if showers become
more concentrated. Eventually storm chances increase more into
Monday afternoon/evening which would support possible sub-VFR
conditions. Wind fields remain south to perhaps southeasterly.

Generally expecting VFR conditions through the long term period.
However, each day will come with an increasing chance of
afternoon/evening thunderstorms. This will bring a chance for
restrictions at any of the terminals.

&&

.MARINE...
Wind fields through Sunday morning remain on the lighter side
given weak gradients in place. South to southeasterly wind gusts
should stay around 10 knots or less with dry conditions
expected. As what remains of Tropical Storm Chantal moves
onshore into the Carolinas, there will be a gradual uptick in
the south-southeasterly flow. Most start to see 10 to 15 knot
gusts for the second half of Sunday, locally up to 20 knots in
the southern waters. As such, channeling effects over these
waters may require Small Craft Advisories from Sunday evening
into the night.

Afternoon/evening thunderstorm chances increase by Monday which
may lead to hazardous marine conditions. In addition to the
potential for frequent lightning, Special Marine Warnings may be
needed for any strong storms. Any convection should wane into
the overnight hours.

Showers and thunderstorms are possible over the waters as a cold
front approaches the forecast area next week. Winds are expected to
stay below SCA criteria on Tuesday and Wednesday, although SMWs are
possible during afternoon showers and thunderstorms. This pattern
will likely continue for the remainder of the week as well.

&&

.TIDES/COASTAL FLOODING...
Light southerly winds will result in slight increases in water
level anomalies over the next several days. While flooding is
unlikely for most areas, Annapolis may near minor flood
thresholds during the overnight high tides, particularly for the
next two cycles (tonight/Sunday night).

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$

SYNOPSIS...BRO
NEAR TERM...AVS/BRO
SHORT TERM...BRO
LONG TERM...CJL
AVIATION...BRO/CJL
MARINE...BRO/CJL
TIDES/COASTAL FLOODING...