FXUS61 KLWX 061927
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
327 PM EDT Sun Jul 6 2025
.SYNOPSIS...
High pressure will continue to move offshore today while the
remnants of Chantal moves across North Carolina. This remnant
low pressure will weaken Monday while a cold front approaches
from the northwest. This front will stall nearby through much of
the week ahead, potentially even into next weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
With high pressure pulling away from the Atlantic coast, a
moisture-rich air mass will continue to draw abundant Gulf
moisture into the local area. While dew points were confined to
the low/mid 50s on Friday/July 4th, today's readings are roughly
15 to 20 degrees moister. As of early this afternoon, dew points
have risen into the mid 60s to low 70s. Above average heights
aloft coupled with continued diabatic heating will further usher
temperatures toward the 90 degree mark by later this afternoon.
This appears feasible as the current warm spots are sitting in
the mid 80s.
Ahead of Tropical Depression Chantal which is spinning across
south-central North Carolina, enhanced lift has already begun to
move into the Mid-Atlantic region. While most instability
cumulus are fairly shallow owing to subsidence aloft from the
ridge, a few have grown tall enough to form rain showers. Such
activity is widely scattered and lifting northwestward from the
Northern Neck of Virginia. This cellular convection is fairly
disorganized and rather pulse-like in nature. Looking further
ahead, a better focus for showers lifts toward the central
Virginia Piedmont over into southern Maryland. Total forecast
amounts generally run between 0.10 to 0.25 inches, locally
approaching 0.50 inches in more concentrated cores.
For tonight, a majority of the guidance carry the remnants of
Chantal across south-central Virginia while potentially grazing
Nelson, Albemarle, and Orange counties overnight. Eventually
closer to sunrise, a separate focus sets up along the
Chesapeake Bay where high-resolution models depict a pool of
elevated instability. This activity would then persist into the
morning hours on Monday. Besides the rain chances, light winds
and continued moist conditions will favor patchy fog
development, mainly west of I-95. Tonight's low temperatures
will range from the upper 60s to mid 70s, locally a bit cooler
across the mountains.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Anomalous moisture associated with the remnants of Chantal will
push across the region on Monday. Some ongoing showers are
possible along and over the Cheseapeake Bay. In the presence of
precipitable water values of around 2 to 2.25 inches, the 12Z
HREF solution shows an expanding axis of showers during the late
morning to afternoon hours. A soaking rain is noted, especially
along and east of U.S. 15. While the threat for thunderstorms
will be somewhat diminished, cannot rule out a few rumbles of
thunder during that period. Once this activity clears out during
the mid/late afternoon, there will be a window of opportunity
for additional storms during the late afternoon to evening
period. However, this is likely to be highly dependent on
scouring out earlier cloud cover. Forecast high temperatures on
Monday are in the mid 80s to low 90s, with mid 70s to low 80s in
the mountains.
With the loss of heating and buoyancy in the atmosphere, a bulk
of the diurnally forced activity should wane into the overnight
hours. A seasonably warm and humid air mass remains into the
night with low temperatures in the upper 60s to mid 70s
(slightly cooler across the higher terrain).
Tuesday is presenting itself as a fairly active weather day in
terms of heat, humidity, and possible severe thunderstorms
and/or flooding. The global ensemble consensus paints a broad
area of low/mid 90s across the forecast area, with some of the
more robust temperature forecasts nearing 97 degrees. Given the
degree of clouds and showers developing with daytime heating, do
see mid 90s as a bit of a reach. However, given dew points in
the low/mid 70s, heat indices will be fairly high, generally
ranging between 100 and 105 degrees.
Forecast soundings are quite moist with precipitable water
values nearing 2 inches. Mean westerly flow through the column
could present some challenges to storm development. However,
believe the forcing from approaching shortwaves and other
mesoscale features should help spawn storms amidst 2,000 to
2,500 J/kg of CAPE. Given cells will likely be highly efficient
rain producers (anomalous moisture, freezing levels up to around
15,000-16,000 feet, and tall/skinny CAPE profiles), a flood
risk is certainly present on Tuesday. Depending on how long
instability festers, some storms could linger into the night.
Tuesday night's lows are forecast to be mid 60s to low 70s,
slightly warmer inside D.C. and Baltimore.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
The long term period features a very active period across our
region. Following Tuesday's severe weather threat, the same frontal
boundary will essentially remain stationary over the region through
at least the end of the week. An overall troughy pattern returns to
the eastern CONUS, bringing several pieces of upper-level energy
through the region during this time. Beyond Tuesday, which was
talked about in the short term discussion above, no day really
sticks out from another at this point as a particularly concerning
compared to the next. However, each day will come with the threat
for thunderstorms. The environment in place will have 2+" PWATs,
plenty of instability, and that stalled frontal boundary. All of
these are ingredients ripe for a flooding threat across the region.
Again, at this point it is hard to nail down an exact location, but
worry about training storms with very heavy rainfall rates wherever
the front sets up. Broadly, all days could pose a flooding risk, but
not all areas will see flooding each day. Additionally, as is
typically the case with these summer patterns, any day could produce
a few severe thunderstorms as well. Best day could be Wednesday, and
then again sometime this weekend, but that will all depend on the
timing of the stronger shortwaves. This currently varies amongst
guidance, so hard to pin down at this point. This pattern looks to
linger even into early next week.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
VFR conditions prevail through the remainder of the afternoon
and evening. Will continue to monitor cells lifting
northwestward from the Northern Neck of Virginia. Light winds
and moist conditions at the surface will lead to some patchy
fog. The best shot for any sub-VFR conditions would be across
KMRB, KCHO, and KIAD. The remnant circulation from Chantal may
graze central Virginia overnight before spreading rainfall
across the area late Monday morning into the afternoon. A period
of restrictions is likely during this time, especially from U.S.
15 eastward. Depending on how quickly clouds scour out, some
thunderstorms may spawn during the late afternoon to evening
hours. However, uncertainty remains pretty high at this point.
After a couple of days with mainly south to southeasterly winds,
expect winds to shift to westerly on Tuesday as a cold front
approaches. This also presents a better chance for organized
showers and thunderstorms. Periods of restrictions are looking
more likely given widespread convective activity. Some of these
issues may persist into portions of the night.
Generally expecting VFR conditions through the long term period.
However, each day will come with an increasing chance of
afternoon/evening thunderstorms as a series of upper-level
disturbances moves through the region. This will bring a chance
for restrictions at any of the terminals. Expect a similar pattern
through the end of the week into this coming weekend.
&&
.MARINE...
With south to southeasterly winds strengthening as the remnants
of Chantal pass by to the south, winds turn a bit breezier later
this afternoon and through portions of the overnight hours.
Small Craft Advisories are in place across the southern half of
the Chesapeake Bay and lower portions of the tidal Potomac.
Gusts up to 20 to 25 knots are expected. Winds may remain
elevated through the remainder of the night so these advisories
may need to be extended.
For Monday and particularly Tuesday, an active weather pattern
ensues with increasing convective chances. Special Marine
Warnings will be possible during the afternoon and evening hours
each day. However, it does appear that Tuesday will be the more
active of the two days as a cold front approaches from the
northwest.
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 Wednesday and Thursday, although SMWs are
possible during afternoon showers and thunderstorms any of the days.
This pattern will continue for the remainder of the week as
well.
&&
.TIDES/COASTAL FLOODING...
Light southerly winds are resulting in slight increases in
water level anomalies. While flooding is unlikely for most
areas, Annapolis may near minor flood thresholds during the
overnight high tides, particularly early Monday morning.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 2 AM EDT Monday for ANZ532-533-537-
541.
Small Craft Advisory until 6 AM EDT Monday for ANZ534-543.
&&
$$
SYNOPSIS...BRO
NEAR TERM...BRO
SHORT TERM...BRO
LONG TERM...CJL
AVIATION...BRO/CJL
MARINE...BRO/CJL
TIDES/COASTAL FLOODING...ADS