663
FXUS61 KLWX 251915
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
315 PM EDT Thu Jun 25 2026

.WHAT HAS CHANGED...
A subtle surface trough could ignite a shower or thunderstorm
over the northern Shenandoah Valley this evening, then a few
thunderstorms may approach western Maryland in a weakening state
late this evening. The coverage and intensity of thunderstorms
is a bit uncertain Friday and depends on cloud cover and how
much instability develops. The frontal progression looks a bit
slower leading to higher rain chances longer through the day on
Saturday, with a bit of humidity lingering Sunday. Heat looks to
build next week, but varying magnitudes linger in guidance.

&&

.KEY MESSAGES...
- (1) A cold front will slowly cross the region delivering
  waves of showers and thunderstorms through Saturday.

- (2) Hot and humid conditions are expected next week.

&&

.DISCUSSION...
KEY MESSAGE 1...A cold front will slowly cross the region
delivering waves of showers and thunderstorms through Saturday.

The latest surface analysis places a weak surface trough in the
vicinity of I-81. This trough may be enhanced slightly by
differential heating left in the wake of a band of mid-level
clouds. It is possible that a shower or thunderstorm or two pop
up in the foothills west of I-81 after 4 or 5pm, then drift east
towards Hagerstown-Martinsburg-Winchester this evening. Activity
should wane with the loss of daytime heating and as it bumps
into downstream ridging later this evening approaching US-15.
The environment is characterized by modest instability (MLCAPE 500
J/kg), low-level lapse rates (7 C/km), and mid-level flow (30-40
kts), so if a stronger cell pulsed up it could feasibly result
in 30-45 mph wind gusts.

Meanwhile, a few clusters of convection may develop along and
ahead of a cold front back over the Ohio River Valley. These may
affect western Maryland as this area is closest to a glancing
shortwave later this evening. Some gusty winds or a little hail
are possible if a more organized storm develops upstream and is
able to maintain itself into the Alleghenies. There is a low and
somewhat conditional risk for such storms to produce localized
45-60 mph wind gusts due to a bit more organization and stronger
flow aloft further north and west, but increasing stability with
the loss of daytime heating should limit the threat from
becoming too widespread too late into the night.

The front will slowly sag south into the area, with a tightening
low-level frontal zone late Friday through Saturday afternoon.
Repeated rounds of showers and thunderstorms are possible. Any
residual outflow could help enhance convergence and lift along
the frontal zone (most likely south of I-70) Friday afternoon.
If stronger heating develops along and south of this axis,
lingering mid-level flow of 30-40 kts, steeper low-level lapse
rates, and stronger CAPE/DCAPE could result in downbursts with
the strongest storms (again generally 45-60 mph). Due to
lingering uncertainties in frontal placement, how much flow is
left, and how much instability builds, confidence remains very
low and conditional for severe weather, despite a high
probability of measurable rain and lightning at some point
Friday into Friday night.

Even with the loss of heating, moisture advection over the
slowly sagging front is expected to result in showers and a few
thunderstorms through Friday night into Saturday. The exact placement
of the front becomes even more uncertain by this time, but the
trend is for a bit slower progression. This raises rain chances
well into the day Saturday. Although it likely won`t be a wash
out (i.e. raining the entire time), waves of showers are quite
possible. Any severe weather threat would remain near and south
of the front, which at this point would favor the I-64 corridor
and points south. Confidence is a bit higher in stronger instability
building south of the front, but the northern extent of such
instability remains in question.

Drier though still somewhat humid conditions are expected Sunday
with perhaps a pop up shower or two near the mountains as the
front slowly slides away and weakens.


KEY MESSAGE 2...Hot and humid conditions are expected next week.

By Monday, a large area of upper-level ridging builds over the Ohio
River Valley, allowing for surface high pressure that will
persist over the Mid-Atlantic for several days. Heat likely
begins to ramp up Tuesday and Wednesday, along with elevated
dewpoint temperatures that will produce widespread hot and
humid conditions. Early ensembles indicate heat indices
potentially reaching 100F by Wednesday; although ensemble
temperature data shows some spread by this time, it looks likely
to see an extended period of summertime heat especially with
dewpoints in the upper 60s and low 70s contributing to indices.

This upper-level ridging will allow for temperatures to
increase through late next week. An isolated diurnal shower or two
remains possible depending on the position of the ridge by midweek,
with next chances for a frontal boundary passage occurring late next
week that could bring back additional precipitation chances.


&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
VFR/dry conditions are expected through most of the TAF period,
though can`t totally rule out a pop up SHRA/TS near MRB
23Z-03Z. Winds will be southerly (more SE at MTN) 9-12 kts with
gusts 15-23 kts with the highest gusts most likely 21Z-03Z.
After 19Z or 20Z Friday, SHRA/TS chances increase markedly. A
boundary will slide slowly southward across the area with
moisture advection overrunning it, and this is expected to cause
scattered to numerous showers and a few thunderstorms.

Additional activity is possible through Friday night, with a
chance of remnant TS activity approaching from the OH Valley
late into Saturday morning. Additional activity and lower CIGs
are possible through Saturday as a front slowly slides south.
Wind direction may be a bit variable between S and NW depending
on the placement of the front, but should be generally light
outside of convection.

Prevailing VFR conditions are expected across terminals Sunday
through Tuesday. Light north/northeast winds shift southerly by
Tuesday morning.

&&

.MARINE...
SCAs are in effect for all the waters through tonight. Southerly
winds peak this evening, then gradually diminish through Friday
morning. Showers and thunderstorms are expected at times late
Friday afternoon through Saturday with gusty winds and lower
visibility in and near stronger storms. Winds turn NW behind a
cold front this weekend.

Winds likely remain below SCA thresholds Sunday-Monday,
potentially increasing to marginal SCA conditions on Tuesday
evening. Northeast winds shift southerly by Tuesday morning.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 3 AM EDT Friday for ANZ530-531-538-
     539.
     Small Craft Advisory until 8 AM EDT Friday for ANZ532>534-537-
     540>543.
     Small Craft Advisory from 5 PM this afternoon to 3 AM EDT
     Friday for ANZ535-536.

&&

$$

DISCUSSION...DHOF/SRT
AVIATION...DHOF/SRT
MARINE...DHOF/SRT

NWS LWX Office Area Forecast Discussion