342
FXUS61 KLWX 021358
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
958 AM EDT Sun Aug 2 2026
.WHAT HAS CHANGED...
Have increased shower chances this morning across central
Virginia up into the eastern West Virginia panhandle per ongoing
radar trends. Although rainfall amounts of 1 to 1.50 inches are
being observed in only 30 to 45 minutes, there have been no
flood reports at this time.
&&
.KEY MESSAGES...
- 1) Locally heavy rainfall could lead to instances of flash
flooding this afternoon into tonight.
- 2) Sustained shower and thunderstorm chances continue through
the end of the week.
&&
.DISCUSSION...
KEY MESSAGE 1...Locally heavy rainfall could lead to instances
of flash flooding this afternoon into tonight.
A large upper trough over the western OH Valley this morning is
progged to slowly move east toward the Mid-Atlantic through the
early part of this week. While the main mid-level energy of this
system will pass by north of our area on Monday, a trailing wave of
vorticity will stretch south along the Appalachians into the Deep
South. A weaker cutoff mid-level low develops somewhere near the
southern Appalachians Monday night. An associated surface boundary
moves into the northern half of the area tonight, then stalls nearby
through at least Tuesday before possibly lifting north as a warm
front. To our east the Bermuda High remains squarely in place across
the western Atlantic. Southerly flow is advecting deep tropical
moisture into the Mid-Atlantic today, with PWATs well over 2".
For this morning, showers are already ongoing off to the west of
I-95. The thermodynamic environment is very moist being
characterized by a PWAT value of 2.16" (per 12Z IAD sounding)
which is fairly close to the daily maximum. Unsurpisingly,
current shower activity along/east of I-81 have been efficient
rainfall producers. A few personal weather stations in central
Virginia reported 1 to 1.50 inches of rain in about 30 to 45
minutes. Will continue to monitor the incoming 12Z guidance to
determine whether Flood Watches need to be expanded eastward.
Many additional rounds of showers and thunderstorms are
expected to develop through tonight. The very moist environment
will favor abundant low clouds which result in lower instability
values, though cloud breaks could produce some areas of
additional destabilization. SPC has maintained the Marginal Risk
(level 1 of 5) for severe thunderstorms today. Given the
saturated environment, water-loaded downdrafts capable of strong
winds are going to be the main severe threat.
The likely higher threat is going to be the potential for flash
flooding. Areas that see multiple rounds of heavy showers and
thunderstorms will be most at risk, especially urban and poor
drainage areas. A Flood Watch has been coordinated with the
surrounding offices for areas along the Blue Ridge, central
Shenandoah Valley, and Alleghenies.
For the Alleghenies, the time period of highest concern is likely
this afternoon as the frontal boundary moves into the area. Given
the orientation of the boundary and how storms will progress along
it (from southwest to northeast), there is the potential for
training thunderstorms. A similar, though lower confidence scenario,
could play out in the central Shenandoah Valley and along the Blue
Ridge. Terrain enhanced convection could produce localized higher
rain amounts on the eastern slopes of the ridge. Overall, rain
amounts of 1-2" are likely, with localized higher amounts of 3-4"
possible.
For the DC and Baltimore Metro areas, there is concern for flooding
as multiple rounds of showers/thunderstorms move through late this
afternoon into tonight. However, confidence remains low regarding
exactly where any heavier thunderstorms develop. We will continue to
analyze new model data this morning, so it is possible the Flood
Watch is extended east into the metro areas. Showers and a few
thunderstorms likely persist well into tonight, especially east of
the Blue Ridge.
KEY MESSAGE 2...Sustained shower and thunderstorm chances
continue through the end of the week.
For the start of the work week shower and thunderstorm chances
continue each afternoon and evening as we sit within the warm
sector. Meanwhile, waves of low pressure will continue to pivot
through as a stalled boundary sits just south and east of the area.
Additional concerns for flooding may develop as the week progresses.
Daily shower and thunderstorm chances continue through the end of
the week as an upper level low stalls over the Appalachians before
slowly tracking eastward. As this system finally pushes offshore
towards the end of next week, the lingering frontal boundary could
produce potentially increased chances for severe weather. Medium-
range machine learning outputs show an enhanced possibility between
Thursday and Saturday as this system transitions offshore. As PWATs
will remain elevated during this period (ranging between 1.5-2.1
inches), heavy rainfall as well as gusty to damaging winds will be
likely hazards with any severe storms that do form. Given persistent
ongoing drought within the region, flood threats will likely be
isolated to poor drainage areas during any periods of sustained
heavy rain.
As this system stalls just south of the region during the week,
temperatures will slowly increase and, combined with increased
humidity during this period, could bring back elevated heat indices
in the upper 90s across the metros beginning Wednesday. High
pressure moves in overhead once any lingering frontal boundaries
push offshore.
&&
.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
Sub-VFR conditions are likely to develop by this evening across the
areas as low clouds slowly settle over the region. Showers are
already moving in this morning, some of which have produced
restrictions at KCHO and KMRB. Multiple rounds of heavy showers
and thunderstorms are expected this afternoon to evening. TEMPO
groups have been added to most of the TAFs, though there is
still uncertainty regarding exact timing for the worst impacts.
A period of steady showers is expected this evening into the
first half of tonight.
While some improvements are likely by Monday morning, the stalled
frontal boundary over the region will maintain low clouds and
passing showers. Additional rounds of afternoon to evening
thunderstorms are likely each day.
Sub-VFR conditions will likely continue to be intermittent at
terminals throughout the week as daily shower and thunderstorm
chances persist, particularly in the afternoon & evening timeframe.
South to southwesterly winds flow Wednesday and through the end of
the week.
&&
.MARINE...
Southerly flow across the waters is producing SCA conditions this
morning. Expect winds to remain elevated through tonight, then
slowly taper off by Monday morning. Multiple rounds of heavy
showers and thunderstorms will move across the waters this
afternoon to evening. Special Marine Warnings may be needed for
thunderstorms capable of producing wind gusts in excess of 35
knots. While winds are likely to remain below SCA levels Monday
and Tuesday, there will be additional afternoon to evening
thunderstorms each day.
Southerly channeling over the waters could produce SCA conditions in
the afternoon/evening hours both Wednesday and Thursday. A few
showers & thunderstorms are possible over the waters during this
period due to a stalled front nearby.
&&
.TIDES/COASTAL FLOODING...
Tidal anomalies continue to rise, with sensitive locations reaching
Action Stage to Minor Flood Stage during the astronomical high
tide this morning. A Coastal Flood Advisory continues for
Annapolis although water levels have begun to come down. South
winds are forecast to persist for much of the week, so
additional periods of coastal flooding are possible.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 8 AM EDT Monday for MDZ008.
Coastal Flood Advisory until 10 AM EDT this morning for MDZ014.
Flood Watch through late tonight for MDZ501-502-509-510.
VA...Flood Watch through late tonight for VAZ503-504.
Flood Watch from 2 PM EDT this afternoon through late tonight
for VAZ025>027-029-036>040-507-508.
WV...Flood Watch through late tonight for WVZ050-055-501>506.
MARINE...Small Craft Advisory until 8 AM EDT Monday for ANZ530>534-
537>543.
Small Craft Advisory until 11 PM EDT this evening for ANZ535-
536.
&&
$$
DISCUSSION...BRO/KRR/SRT
AVIATION...BRO/KRR/SRT
MARINE...BRO/KRR/SRT
NWS LWX Office Area Forecast Discussion