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853
FXUS61 KLWX 121955
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
355 PM EDT Sat Jul 12 2025

.SYNOPSIS...
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High pressure will remain in place offshore through the upcoming
week. A weakening cold front will move through on Monday, before
stalling out and dissipating. A stronger cold front will
approach from the northwest by next weekend.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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A very warm and humid airmass remains in place across the area
today, with isolated showers and thunderstorms ongoing. It`s
expected that activity should remain isolated through the
remainder of the afternoon, with an overall lack of forcing on
the synoptic scale, and the presence of mid-level dry air evident
on the 12z IAD sounding. Flow aloft is very weak, so storms
have been relatively disorganized and driven by outflows. This
will continue to be the case through the remainder of the
afternoon and evening, before activity winds down after dark.

The background environment is rather favorable for downburst
winds, with around 2000-3000 J/kg of MLCAPE and 900-1300 J/kg
of DCAPE present per SPC mesoanalysis. SPC has much of the area
outlooked in a Marginal Risk for severe thunderstorms. Storms
will also be capable of producing heavy rainfall. With heavy
rainfall rates and slow storm motions, an instance or two of
flash flooding may also be possible. However, the presence of
ample DCAPE suggests that storms may have strong enough outflow
to rapidly stabilize the boundary layer, potentially limiting
the time that a storm may be able to persist in any single
location. Activity should gradually wind down through the
evening hours with loss of daytime heating, giving way to dry
conditions during the second half of the night. Low clouds will
move in to the east of Blue Ridge, and some patchy fog may be
possible as well, especially to the west of the Blue Ridge.
Overnight lows will be in the upper 60s to mid 70s.
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&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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A potent shortwave and associated area of low pressure at the
surface will track northeastward toward Hudson Bay tomorrow.
We`ll actually experience slight height rises aloft as this
occurs, but the low-level mass response associated with the
surface low will lead to increased moisture (PWATs increasing to
near or above 2 inches) and low-level convergence. Model
guidance is in good agreement that storms will develop along a
well-defined surface trough over the Potomac Highlands and
Shenandoah Valley during the early to mid afternoon hours. Those
storms will then slowly track eastward, reaching the US-15
corridor by around 5 or 6 PM, and then start to weaken as they
approach the I-95 corridor around sunset.

Model soundings show around 2000-3000 J/kg of MLCAPE, around
600-800 J/kg of DCAPE, 10-15 knots of effective bulk shear, and
PWAT values increasing to near 2 inches. The lower DCAPE values
may temper the potential for downbursts in storms tomorrow, but
the overall higher coverage of storms and higher PWAT values may
still make water loaded downbursts possible. SPC currently has
much of the area outlooked in a Marginal Risk for severe storms.
With PWAT values approaching 2 inches and significant
instability present, storms should be capable of producing very
heavy rainfall. That coupled with slow storm motions may make
flash flooding possible tomorrow as well. WPC has much of the
area outlooked in a Slight Risk for Excessive Rainfall tomorrow.

A decaying cold front associated with Sunday`s system will drop
southward into the area on Monday, before eventually stalling
out. Various sources of guidance differ with respect to where
this boundary will set up, but additional showers and
thunderstorms appear likely along and southeast of the boundary
within the deepest moisture. Continued heat and humidity will
persist Sunday into Monday, with high temperatures around 90,
low temperatures around 70, and dewpoints in the low to mid 70s.
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&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
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An active weather pattern looks to continue through the end of next
week, with daily chances for showers and thunderstorms. Mid-level
ridging centers over the Carolinas by mid to late week as the axis
of the Bermuda High builds toward the southwest Atlantic. The
stalled frontal boundary over the area Tuesday lifts north as a warm
front. The region then remains in a hot and humid airmass the rest
of the week as numerous shortwave troughs traverse overhead. The
moist airmass could favor thunderstorms capable of producing heavy
downpours and localized flooding. Depending on the location or
development of local mesoscale features, there could be some
possible strong to severe storms. While uncertain at this time,
Tuesday and Wednesday look to have the best chance for that. Highs
will be in the upper 80s to low 90s, with heat indices in the
low 100s.
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&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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Prevailing VFR conditions are expected this afternoon into this
evening. Temporary drops to sub-VFR conditions may be possible
in thunderstorms. Overall, the coverage of storms is expected to
be low, so have opted for PROB30s (MRB, CHO, IAD, DCA) or no
mention at all (BWI, MTN) this afternoon. Any thunderstorms
should gradually wind down through the evening hours. Low clouds
will move in during the second half of the night tonight, with
IFR conditions possible late tonight through the first half of
tomorrow morning. Conditions should gradually improve back to
VFR by the late morning/early afternoon hours. Coverage of
thunderstorms is expected to be much higher tomorrow, with MRB,
CHO, IAD, and DCA being the most likely to experience impacts.
Storms could potentially weaken or dissipate altogether before
reaching BWI and MTN. Showers and thunderstorms may also be
possible on Monday, with CHO standing the greatest chance.

Winds will be out of the southeast through the day tomorrow,
before becoming light and somewhat variable in the vicinity of
a decaying cold front on Monday.

Daily afternoon to evening showers and thunderstorms are in the
forecast through the middle of next week. These storms could produce
brief periods of sub-VFR conditions if they move over a terminal.
Outside of shower/thunderstorm activity, VFR conditions prevail.
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&&

.MARINE...
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Sub-SCA level southeasterly winds are expected through Sunday,
before winds become light and variable on Monday. SMWs in
association with thunderstorms may be possible each afternoon
or evening through Monday, but coverage of storms should be low
today, and there`s a good chance that storms may decay tomorrow
evening before reaching the Bay.

Southerly winds around 10 knots prevail Tuesday into Wednesday.
Daily afternoon to evening thunderstorms could be a hazard to
mariners with gusty winds and lighting strikes likely. Southerly
channeling Wednesday night could bring winds near SCA levels over
the open waters of the Chesapeake Bay.
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&&

.TIDES/COASTAL FLOODING...
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A prolonged period of southeasterly winds will lead to elevated
tidal anomalies over the weekend and into early next week. This
carries most of the tidal locations into Action stage,
particularly during the higher of the two astronomical high tide
cycles. Sensitive locations, such as Annapolis, are forecast to
hit Minor stage during the high tide cycle Sunday and Monday
mornings.
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&&

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

&&

$$

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