Office: LWX
FXUS61 KLWX 070805
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
405 AM EDT Mon Jul 7 2025
.SYNOPSIS...
The remnant low pressure from Chantal will weaken as it crosses
the area today, while a cold front approaches from the northwest.
The front will drop closer to the area Tuesday and may stall
nearby through the weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
Current analysis places the remnants of Chantal near Buggs
Island Lake on the VA/NC border. Moderate to heavy rain is
lifting into south central VA but has shown some signs of
weakening as the overall system weakens. However, the fringes of
this rain will graze southern parts of the forecast area through
the early morning hours, with the heaviest expected to stay
south of the CWA. Farther north, more isolated showers have
developed, and expect that to remain the case over the next few
hours. Otherwise, expanding cloud cover will limit sun to start
the day.
The remnant low will continue to track northeast through the day
before passing northeast by early evening. There may be a bit of
a gap in the heavy rainfall as the system continues to weaken
along with the diurnal minimum in instability. By late morning
into the afternoon, greater instability and convergence may
occur near the Chesapeake Bay, with embedded heavy convective
elements redeveloping. The strongest signal for heavy rain is on
the Eastern Shore, but CAM guidance suggest localized totals up
to 5 inches could occur on the western shore as well. This
system has a history of producing much more than that in NC and
will be accompanied by an anomalously moist atmosphere with deep
warm cloud layers that will support very efficient rain.
Therefore have issued a Flood Watch for potential flash flooding
along the Chesapeake from 10 AM until 6 PM, which rainfall
should have departed.
Farther west, some clearing will take place. A cold front will
be approaching from the Great Lakes, but should remain northwest
of the area. However, a prefrontal trough and terrain
circulation may support isolated to scattered
shower/thunderstorm developing during the afternoon. At this
time, severe weather and flooding appear unlikely with this
activity. Any convection will likely dissipate as it pushes
toward the metro areas during the early evening. Remnants of
upstream convection may move into the Allegheny Front this
evening as well, but should dissipate with loss of daytime
heating. Speaking of which, cloud cover should keep highs in the
80s near and east of I-95, with lower 90s to the west. Heat
indices may reach the upper 90s.
Other than a few showers along the Alleghenies, tonight should
largely be dry. Some patchy fog could develop. The muggy dew
points will limit lows to the lower and mid 70s except in the
higher elevations.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Shower and thunderstorm coverage will be much greater Tuesday
afternoon and evening as the front moves closer to the area and
subtle ripples move through the WSW flow aloft. A hot and humid
airmass will support moderate to strong instability, so a few
severe thunderstorms with damaging winds may occur. However,
modest shear and moist profiles (limiting DCAPE) may limit the
severe threat. High precipitable water values and deep warm
cloud layers will support heavy rain. There may be enough flow
aloft for storms to be somewhat progressive, but any sort of
merging or backbuilding on the mesoscale would produce a
localized flooding threat. Before storms arrive, heat index
values may reach the upper 90s and lower 100s. While marginal,
Heat Advisories can't be ruled out for portions of the area.
Dry weather likely returns by the second half of Tuesday night.
There's some uncertainty on where the front ends up Wednesday,
but could bisect the area. Model consensus places the highest
chance of storms across the southern half of the area, but all
locations could see some rain. The main threat will be heavy
rain/localized flooding given the continued moist environment,
but a localized damaging storm can't be ruled out. Very warm and
humid conditions continue with highs in the upper 80s and lower
90s. Storms will likely follow a diurnal trend again.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
A frontal boundary will remain stalled across the region
through the end of the week. Several pieces of upper level
energy and affiliated surface low pressure systems will move
along this front. High precipitable water will fuel numerous
showers and strong thunderstorms nearly each afternoon and early
evening. The multiple rounds of showers and thunderstorms,
energy and moisture available could lead to severe weather and
possible flooding. High temperatures each day will be near
average.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
MVFR ceilings are spreading across the area this morning, with
LIFR conditions at CHO. Mainly isolated showers are expected
through the early morning. Steadier and more moderate rains
associated with the remnants of Chantal will graze CHO and the
metro areas today, with the greatest chance of heavier showers
and thunderstorms near BWI/MTN. Ceilings should improve by
midday. Winds will likely be somewhat variable due to the
weakening low pressure system. Additional isolated to scattered
thunderstorms may form over the mountains this afternoon,
potentially affect MRB and CHO. It's uncertain if these reach
the metro areas, but IAD and perhaps DCA will be most at risk,
so maintained PROB30 groups.
Tonight should be dry with light winds. There isn't a strong
signal for fog, but can't rule out some patchy spots.
Thunderstorm coverage will likely be fairly widespread Tuesday
afternoon and evening with heavy rain and gusty winds being
threats. Patchy fog could again form Tuesday night.
Thunderstorm chances will continue each day Wednesday through
Friday, focused on the afternoon and evening. Some low clouds or
fog could develop during the overnight and morning periods given
the moist airmass.
&&
.MARINE...
Marginal SCA conditions on the wide waters of the middle bay are
expected through mid morning before the remnants of Chantal
cross the waters while weakening. The remnants may bring some
heavy rain and embedded thunderstorms through this afternoon.
Generally sub-SCA winds are expected Tuesday, though some
isolated gusts to 20 kt can't be ruled out. More widespread
coverage of thunderstorms is expected during the afternoon and
evening hours, which could bring strong wind gusts.
Sub-SCA winds are most likely Wednesday through Friday. Any
strong thunderstorms crossing the waters could result in Special
Marine Warnings.
&&
.TIDES/COASTAL FLOODING...
South to southeast winds have caused anamolies to rise to
around one foot or a little higher. This is resulting in minor
flooding at Annapolis. After the remnants of Chantal pass today,
water levels are forecast to decline a bit through the middle
of the week. No additional flooding is forecast, although some
locations may reach action stage.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Flood Watch from 10 AM EDT this morning through this afternoon
for MDZ008-011-014-017-018-508.
Coastal Flood Advisory until 6 AM EDT early this morning for
MDZ014.
VA...None.
WV...None.
MARINE...Flood Watch from 10 AM EDT this morning through this afternoon
for ANZ530.
Small Craft Advisory until 10 AM EDT this morning for ANZ534-
543.
&&
$$
SYNOPSIS...ADS
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...KLW
AVIATION...ADS/KLW
MARINE...ADS/KLW
TIDES/COASTAL FLOODING...ADS
