153
FXUS61 KLWX 032206
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
606 PM EDT Thu Sep 3 2026

.WHAT HAS CHANGED...
A Severe T-Storm Watch is in effect for portions of western MD and
the eastern WV midnight. Monitoring two clusters of storms: one of
which northwest of Pittsburgh and another back toward Erie,
PA/Cleveland. This activity will sag south and east between
7-8pm.


&&

.KEY MESSAGES...
- 1) Hot temperatures, high humidity, and severe thunderstorm
chances look to continue through Friday.

- 2) Mostly dry conditions and lowering humidity for the Labor Day
holiday weekend ahead.

&&

.DISCUSSION...
KEY MESSAGE 1...Heat, humidity, and severe thunderstorm chances look
to continue through Friday.

A Severe T-Storm Watch is in effect until midnight for portions
of far western MD and the eastern WV mountains. Damaging winds,
large hail, and locally heavy rainfall will be the primary
threat with these storms as they push south from western PA
between 7-9pm. Further watch expansion may be needed given the
supportive environment for storms.

Overall monitoring two clusters of storms (MCSs) one of which
is coming into Pittsburgh, PA/Wheeling, WV now with another
punching toward Cleveland, OH. Both of these storm complexes
will have plenty of instability to work with given pooling
MLCAPE values of 3000-4000 j/kg. Locally, mid-level lapse rates
of 6.5-7 C/km (per latest mesoanalysis and the KIAD 12Z RAOB)
atop a very moist boundary layer with surface dew points well
into the 70s F will lead to increasing CAPE despite the late
start at surface heating. The question then becomes just how
organized upstream storms become, and how stable the boundary
layer is heading further into the evening. A more organized and
potent line of storms a bit earlier in the evening would result
in a notably higher risk for more numerous damaging wind gusts,
especially focused along the residual baroclinic zone/theta-e
gradient which should lie near the Potomac River/US- 50/I-66
this evening. A somewhat slower and/or more disorganized line
would result in a lower risk for severe surface gusts, though
some isolated damaging winds would still be possible given high
CAPE/DCAPE and the shallow nature of the stable layer near the
surface. Areas of western Maryland and perhaps into the eastern
West Virginia panhandle are most likely to see the storms prior
to the onset of appreciable nocturnal boundary layer stability.

The area remains in a Slight Risk (level 2 out of 5) for severe
weather from SPC as of the 20z/4pm outlook update, driven mostly by
the threat of damaging wind gusts. There is a threat for large hail
in stronger cores, though mid-level lapse rates will gradually
become less steep tonight. A linear storm mode would tend to be less
favorable for large hail production (as opposed to
discrete/individual cells), as well. A few discrete cells are
possible this evening in weak low-level WAA, however, independent of
any linear system that may affect the region. These storms would be
most likely to develop over northern and central Virginia into
central Maryland along a weak surface trough and the aforementioned
moisture/instability gradient.

Current timing has this initial round of storms into western MD and
eastern WV between 7-9pm gradually advancing east toward
northern and central MD and northern VA between 9pm-midnight.
The secondary complex of storms will push south and east mostly
likely after 10pm- 2am. Pending how much energy the first
complex of storms zaps away combined with the nocturnal stable
layer will determine how of the secondary complex survives. The
severity may drop off although gusty winds, frequent lightning,
and locally heavy rainfall will remain the primary concerns.

Additional showers and thunderstorms, possibly strong to severe, are
anticipated again on Friday. Timing is a bit uncertain given the
subtle waves aloft, but increasing low-level convergence paired with
another upper impulse may very well result in another round or two
of storms with a damaging wind risk. The latest guidance has nudged
the threat a bit further north, encompassing areas as far north as I-
70 or the Mason-Dixon line (as opposed to I-66/US-50). This will
depend on any residual early day clouds or convection, of course.

Lows tonight will fall into the upper 60s and mid 70s with heat
index values in the mid 70s and low 80s. Highs Friday will
range from the upper 80s to lower 90s with dew points in the
lower to middle 70s resulting in heat indices in the upper 90s
to lower 100s. This will be just shy of heat headline criteria
(except in Charlottesville and surrounding Albemarle/Nelson
Counties). The potential for early day clouds to offset heating
precludes enough confidence to issue any further heat headlines
at this time, though it will be unusually hot and humid for
early September regardless.


KEY MESSAGE 3...Drier conditions expected for the Labor Day weekend
through early next week.

A high pressure system over the Great Lakes continues to track
southeastward towards our forecast region through Tuesday. Over this
time period, condtions remain predominantly dry, apart from
 an isolated shower in the Appalachian mountains.

Temperatures remain seasonable for early September this weekend,
with temperatures rising above normal by Tuesday. Moist and warmer
conditions return as we head into the middle of next week. Warm,
moist air at the surface could lead to unstable conditions, with
chances for showers and thunderstorms returning by late Wednesday.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
VFR conditions look to prevail through at least 23z/7pm for most of
the corridor. Watching a complex of storms up around KPIT that
looks to dive into areas west of MRB/HGR between 00-02z/7-10pm.
This activity will gradually sags south and east toward the
rest of the corridor beyond 00-03z/8-11pm. Utilized PROB30s
between 01-06z/9pm-2am to encompass this threat as the complex
of storms drops south and east from southwest PA. Gusty winds
and frequent lightning will be the primary threat with any
storms that develop. Some uncertainty remains in regards to the
severity of storms as they push to the eastern end of the
corridor and down toward KCHO/KSHD.

Winds will vary between W and SW as a surface trough develops
overhead with speeds generally AOB 10 kts. Guidance is not keen on
low clouds or fog overnight into early Friday, though the pattern
would suggest at least some conditional potential.

Additional storms with somewhat uncertain timing are possible
Friday. Was too low on confidence in timing for 18Z TAFs, but
PROB30s are likely to be included in subsequent updates, focused
probably on the typical peak diurnal window (~19Z-01Z). Winds will
shift to NW by late Friday through Saturday.

This weekend into early next week, prevailing VFR conditions are
expected across all terminals. Light northeasterly winds on Sunday
shift easterly by Monday.

&&

.MARINE...
Special Marine Warnings may be needed this evening as storms
develop and track towards the waters. Additional storms are
anticipated on Friday, most likely late afternoon and evening.
Otherwise, generally light flow is expected into the upcoming
weekend, though NW gusts could approach SCA levels Friday night
into Saturday.

On Sunday and Monday, wind gusts remain below SCA-criteria with
highest chances for approaching SCA thresholds Sunday afternoon or
evening. Light northeasterly winds on Sunday shift easterly by
Monday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...Heat Advisory until 7 PM EDT this evening for VAZ036-037.
WV...None.
MARINE...None.

&&

$$

DISCUSSION...DHOF/EST/KVH
AVIATION...DHOF/EST/KVH
MARINE...DHOF/KVH

NWS LWX Office Area Forecast Discussion