046
FXUS61 KLWX 241359
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
959 AM EDT Fri Apr 24 2026

.WHAT HAS CHANGED...
Conditions coming together for a round of showers and
thunderstorms along a developing thermal/moisture gradient that
is lined up along the Potomac River. Most likely threat appears
to be for Special Marine Warnings over the waters.

&&

.KEY MESSAGES...
1) A frontal boundary will linger nearby through Saturday, leading
to chances for showers and thunderstorms at times.

 2) High pressure builds in early next week, before the next system
approaches from the west on Tuesday.

&&

.DISCUSSION...
KEY MESSAGE 1...A frontal boundary will linger nearby through
Saturday, leading to chances for showers and thunderstorms at times.

The leading edge of a backdoor cold front has started to move
into northeast MD, with northeast winds noted along/northeast of
a line from Annapolis to Westminster. There is a very noticeable
moisture gradient along the Potomac River, dew points are in the
40s to the east, and in the 50s to the west. The morning IAD
sounding shows around 30 kt of low level winds just off the
surface, with relatively weak flow above and below. Seeing this
convergence zone already leading to some cloud development from
Hagerstown/Martinsburg south to Fairfax. The clouds are mostly
laminar, an indication of stability, but the expectation is for
that inversion to mix out this afternoon as deep mixing ensues.
This is happening in a narrow corridor, that is lining up with a
subtle shortwave trough dropping into the area from western PA.

Along the narrow corridor of convergence (lines up generally
along the Potomac River), models indicate roughly 400-600 J/kg
of SBCAPE will develop as temps reach the low 80s and dew points
remain in the mid 50s. Deep layer shear is almost non-existant,
however, there is roughly 20-25kt of 0-1km shear (all speed
shear) due to the increase in winds in the 950-900mb layer. The
HRRR and RRFS indicate isolated to scattered convection
developing along the convergence/thermal/moisture gradient along
the Potomac, with showers and thunderstorms moving to the
southeast. Initiation looks to be around 1-2pm. Low-level lapse
rates will be steep, around 8-9 C/km, and DCAPE values around
600-800 J/kg with what could end up being an inverted v-shape
sounding (based on model data). While the overall severe threat
is low, cannot rule out a couple of stronger thunderstorms if
more robust convection is able to develop.

As thunderstorms push off the main initiating boundary they will
encounter a more stable boundary layer environment to the east,
so convection likely wanes by 5-6pm this afternoon. For those in
Central VA and the Alleghenies, conditions today likely remain
dry due to subsidence in those areas.

Any additional threat for thunderstorms should largely wane
after dark with the loss of diabatic heating. After seeing
today`s highs push into the mid 70s to mid 80s, temperatures
will come crashing down on Saturday as the frontal zone sags
southward.

Overnight conditions will be overcast with low temperatures in
the low/mid 50s. By early Saturday morning, the parent front is
forecast to be along or just south of I-64. A cool easterly
flow will make for a chillier day to the north of this boundary.
Rain chances remain plentiful as moisture and lift overrun this
quasi-stationary baroclinic zone. For those along/north of I-66
and U.S. 50, mid 50s to mid 60s are expected (coolest over
northeastern Maryland). Closer to the I-64 corridor, highs could
near 80 degrees although this is dependent on whether the area
remains in the warm sector or not.

Some rain chances continue into the evening as well as Saturday
night. Forecast lows will be cooler than the previous night with
widespread temperatures in the 40s.


KEY MESSAGE 2...High pressure builds in early next week, before the
next system approaches from the west on Tuesday.

The aforementioned upper level disturbance will progress off to our
east on Sunday, causing showers to wind down from west to east
during the morning hours. Upper ridging will build in its wake, and
hold strong overhead through much of Monday and Tuesday. However,
high pressure will remain in place to our northeast. As a result,
persistent onshore flow is expected. This should lead to below
normal temperatures and more in the way of clouds than sun.
Temperatures on Sunday, Monday, and Tuesday should reach up into the
60s during the day, and then drop back into the 40s at night.

An upper trough and associated surface low will track into the Great
Lakes on Tuesday. As of now, it looks like we`ll stay stable, so
just showers are expected Tuesday afternoon into Tuesday night as
large scale ascent ahead of that system overspreads the area.

&&

.AVIATION /13Z FRIDAY THROUGH TUESDAY/...
VFR conditions are expected across all terminals through the
morning hours, with initial light winds given weak gradients.
Isolated to scattered showers and thunderstorms break out this
afternoon as peak heating commences. This could yield some
restrictions at any of the TAF sites, mainly in the 2-6 PM
timeframe. Any issues related to convection should wane toward
nightfall.

The meandering frontal zone slowly pushes south of the area
overnight yielding a steady easterly winds into Saturday. This
increase in maritime influences will yield lowering ceilings and
further rain chances. Sub-VFR conditions are looking likely
across much of the region on Saturday. Based on aviation
guidance, daytime conditions could even lower to IFR at times.
Low ceilings persist into Saturday night with widespread IFR
conditions likely. Winds eventually shift to northeasterly as
high pressure builds to the north. A few showers are possible,
but expect improvement to flight conditions on Sunday.

Light winds Monday morning become easterly, blowing 5 to 10 knots in
the afternoon. Winds become southeasterly overnight before shifting
to the south and gusting around 15 knots Tuesday afternoon. Daily
precipitation chances will lead to possible flight restrictions with
thunderstorms possible on Tuesday.

&&

.MARINE...
A frontal zone currently stretches north of the waters up across
central Pennsylvania. Weak gradients will keep marine winds
below advisory thresholds. Isolated to scattered convection may
fire up this afternoon with daytime heating. A couple of the
more robust cells would be capable of Special Marine Warnings
given some downburst potential.

As the frontal zones sags southward across the area, winds shift
to easterly tonight into Saturday. Winds could approach 20 knots
over the southern waters by early Saturday before becoming more
widespread through the day. Consequently, Small Craft Advisories
will likely be needed across most marine zones on Saturday.
Winds further increase in strength on Saturday night with a
shift to northeasterlies. Gusts up to 20 to 25 knots are
possible. As high pressure builds to the north, local marine
wind fields shift to northerly with channeling effects possible
on Sunday. Additional Small Craft Advisories will likely be
needed.

East winds remain below Small Craft Advisory criteria on Monday
before becoming shifting to southeast and then southerly overnight
into Tuesday. Small Craft Advisories are possible Tuesday afternoon
as winds near criteria. As a cold front approaches and crosses over
the waters, thunderstorms are possible. SMWs may be needed Tuesday
afternoon.

&&

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

&&

$$

DISCUSSION...AVS/BRO/KJP/EST/KRR
AVIATION...AVS/BRO
MARINE...AVS/BRO

NWS LWX Office Area Forecast Discussion