644
FXUS61 KLWX 041434
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1034 AM EDT Thu Sep 4 2025

.SYNOPSIS...
A frontal system will approach from the west today, but will
weaken as it moves into the area tonight. Weak high pressure
will move across the area Friday. A stronger cold front will
reach the area Saturday. High pressure of Canadian origin will
build north of the area early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Mid-morning update: Radar imagery shows showers just starting to
reach the Allegheny Front and Potomac Highlands, with dense
overcast trailing this activity. Further east, skies remain
sunny. This activity appears to be about 90 minutes ahead of the
progression advertised by most of the 00/06z CAMs. This faster
progression casts some uncertainty regarding whether locations
to the west I-81 will be able to destabilize enough to get
thunderstorms before the dense overcast moves in from the west.
As a result, the greatest chance for stronger storms is expected
to be east of I-81. North-central and northeast Maryland may
ultimately end up with the best overlap of daytime heating and
glancing large forcing as a shortwave lifts off to our
northeast. No significant changes have been made to the previous
forecast. Previous discussion follows...

High pressure extends along the east coast this morning. Low
pressure at the surface and and aloft is located north of Lake
Superior with a cold front extending to the south.

Weakening showers and a few thunderstorms are just reaching the
Allegheny Front. Otherwise the morning should be mostly sunny
across much of the area with strengthening southerly winds with
some gusts of 20-25 mph. The warm advection will push
temperatures into the 80s and dew points into the 60s. Whether
associated with the remnant perturbation from this morning`s
convection or as height falls overspread the terrain and a lee
trough, scattered to numerous thunderstorms will develop by this
afternoon.

These storms will likely impact locations to the west of the
Blue Ridge between roughly noon and 7 PM, and locations to the
east of the Blue Ridge from 2 to 10 PM. Model soundings show
around 500-1000 J/kg of MLCAPE, with around 35-40 knots of
effective bulk shear. Hodographs are relatively straight, with
near unidirectional southwesterly flow. DCAPE appears to be on
the lower side, with relatively moist mid-levels. However, most
models show well mixed sub-cloud layers with relatively steep
low-level lapse rates. CAMs show a mixed multicell/marginal
supercell mode. Small bowing segments may be capable of
producing damaging winds, and any supercells could produce
either damaging winds or hail. Supercell splits may be possible
given the straight hodograph shape. SPC continues to outlook
much of the area in a Marginal Risk for severe thunderstorms.
Storms should be progressive and not pose a flood risk. While
there is still some opportunity for storms to weaken with
eastward extent due to the loss of daytime heating and mid level
lift pivoting northeastward, more guidance is showing fairly
robust storms moving through the metro areas during the early
evening. A second round of convection tied more closely to the
cold front may reach the Appalachians during the late afternoon
or early evening, but these storms should generally fall apart
as they cross the mountains.

The surface front will be in a weakening state as it reaches
the area overnight. Skies should clear, which may promote fog
development in outlying areas as winds become light. Lows will
range from the mid 50s to mid 60s.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
The front will essentially dissipate Friday as height rises
will ensue aloft between disturbances. Southerly flow resumes,
and it will actually turn out warmer with highs in the mid 80s
to near 90. While dry conditions should prevail, a few models
indicate a stray shower popping up during daytime heating. Some
additional showers or thunderstorms may approach the
Appalachians Friday night ahead of the next system.

A stronger cold front will approach the area Saturday ahead of
notable height falls across the Great Lakes. Most models
indicate greater instability developing ahead of the front
compared to today as temperatures again reach the mid 80s to
near 90 with dew points well into the 60s. The highest shear may
lag behind the front, but there should be sufficient shear for
an organized severe weather threat. The main limiting factor
will be mid level lapse rates, as well as how quickly clouds and
showers move into the area. SPC has highlighted a marginal risk
east of I-81 where the greatest heating should take place. Some
showers may linger into Saturday night as the frontal zone
slowly works across the area.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Some uncertainty exists with how quickly the front departs
Sunday as a shortwave crosses the area. Current NBM forecast
lags clearing and keeps low chances of showers, especially
southeast. Otherwise, high pressure builds into the region
Sunday and persists into the start of next week. Dry, much
cooler, fall- like weather returns as highs only reach the low
to mid 70s. Highs in the mid 70s for Monday and Tuesday.
Overnight lows drop to the upper 40s to 50s. Much of next week
should be below climo norms.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
VFR conditions will continue through midday amongst
strengthening southerly winds. Some gusts up to 20-25 kt could
occur during the midday and afternoon. Showers and thunderstorms
will develop ahead of a front this afternoon, potentially
reaching MRB by 2 PM. The window for the remainder of the
terminals will focus on 4-9 PM. The greatest chance for direct
impacts appears to be at MRB and IAD, with coverage potentially
decreasing with eastward and southern extent. Therefore a TEMPO
has been included for these locations with PROB30 elsewhere.
However, if 06Z guidance continues a trend toward better
coverage, may add TEMPOs elsewhere. Some thunderstorms will be
capable of strong to severe outflow winds.

After storms exit, areas of fog may develop especially west of
the Blue Ridge where clearing will likely take place sooner
and rain coverage will be greater. MAV/LAMP guidance indicates
fairly widespread MVFR to IFR ceilings, but is not supported by
other guidance. Have thus only included a FEW group of some lower
clouds for now.

VFR conditions are expected Friday afternoon and evening with
south to southwest winds 5-10 kt. A stronger cold front will
reach the area Saturday. Scattered to numerous showers and
thunderstorms will develop during the afternoon and evening,
some of which could be strong to severe.

High pressure builds in behind the front Sunday into Monday,
bringing VFR conditions and breezy north winds.

&&

.MARINE...
Southerly gusts up to 20 kt are generally occurring in the
narrowed section of the bay between Pooles Island and Drum Point
early this morning. SCA conditions are expected for all waters
within south to southwesterly flow as daytime mixing increases later
this morning and afternoon. SMWs may also be needed late this
afternoon and evening (between 4-10pm) as thunderstorms move
over the waters. While current advisories extend well into
tonight, it`s possible they could end early if thunderstorm
outflows sufficiently disrupt the southerly flow.

There should be a bit of a break in SCA conditions Friday
morning, but marginal advisories could be needed Friday
afternoon into Friday night, especially along the bay where
channeling could enhance the southerly flow.

A cold front will move across the area sometime Saturday, bringing
showers and potentially gusty thunderstorms to the waters.
Southerly winds could remain close to advisory criteria ahead of
the front as well. Behind the front, a period of northerly
channeling could produce SCA conditions Saturday night.

High pressure builds in from the north on Sunday, though northerly
winds could remain elevated through Sunday evening. Northerly winds
continue Monday, but lessen to generally below 10 kts.

&&

.TIDES/COASTAL FLOODING...
Tidal anomalies are around 1 foot this morning, with Annapolis
reaching minor flood. Peak water anomalies appear to occur
tonight ahead of a front in strong southerly flow. More
locations may reach minor flood, and some guidance has Annapolis
approaching moderate flood. A Coastal Flood Warning is in
effect for Annapolis for the tide cycle tonight, and Coastal
Flood Advisories are in effect for many other locations. Water
levels may decrease a bit Friday as the first front fizzles out,
but minor flooding is still possible at a few locations Friday
night as southerly flow strengthens again ahead of the next
front. This front will bring a wind shift Saturday which will
decrease water levels.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 2 AM EDT Friday for MDZ008.
     Coastal Flood Advisory from 2 AM to 8 AM EDT Friday for MDZ011.
     Coastal Flood Warning from 11 PM this evening to 9 AM EDT
     Friday for MDZ014.
     Coastal Flood Advisory from 11 PM this evening to 4 AM EDT
     Friday for MDZ016.
     Coastal Flood Advisory from 10 PM this evening to 4 AM EDT
     Friday for MDZ018.
     Coastal Flood Advisory until 11 AM EDT this morning for MDZ508.
     Coastal Flood Advisory from 6 AM to 11 AM EDT Friday for
     MDZ508.
VA...Coastal Flood Advisory from 11 PM this evening to 4 AM EDT
     Friday for VAZ057.
WV...None.
MARINE...Small Craft Advisory until 2 AM EDT Friday for ANZ530-535-536-
     538>541.
     Small Craft Advisory until 6 AM EDT Friday for ANZ531>534-537-
     542-543.

&&

$$

SYNOPSIS...ADS
NEAR TERM...ADS/KJP
SHORT TERM...ADS
LONG TERM...CPB
AVIATION...ADS/CPB
MARINE...ADS/CPB
TIDES/COASTAL FLOODING...ADS