141
FXUS61 KLWX 081820
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
220 PM EDT Sat Aug 8 2026

.WHAT HAS CHANGED...
Severe thunderstorms ongoing over the Shenandoah Valley and
departing northeast MD at this time.

Added a mention for increased thunderstorm potential on Monday
across all sections of the AFD.

Removed the tides section, as tidal anomalies are not really in
an elevated state anymore.

&&

.KEY MESSAGES...
- 1) Typical Summertime pattern continues with building heat next
week. Storm chances today decreasing Sunday and Monday.

- 2) A cold front could arrive late next week bringing relief
  from the heat and humidity into the upcoming weekend.

&&

.DISCUSSION...
KEY MESSAGE 1... Typical Summertime pattern continues with building
heat next week. Storm chances today decreasing Sunday and Monday.

It`s a typical Summertime pattern as we enter the second weekend and
week of August. The forecast is on repeat with patchy morning dense
fog giving way to hot and humid conditions with late day afternoon
and evening thunderstorms.

Round one of storms has pushed across the MD/PA border this
afternoon, which was very poorly handled by any model guidance.
High CAPE/DCAPE values, steep low-level lapse rates, and 30-35
knots of shear yields a pretty potent organized cluster,
especially in northeast MD. Watching a few clusters of storms
over the Shenandoah Valley this afternoon, which is the round
that was anticipated in previous forecasts. There are a few
question marks now, especially since the prior storms threw an
outflow boundary all the way to the I-66 corridor. As storms
progress east, we will see how any storms interact with said
boundary. High-end today seems to be small, organized bowing
segments with the potential for 60-70 mph wind gusts. This is
due to much more DCAPE today (on the order of 1000 J/kg)
compared to recent days. Still, coverage is much more isolated,
which was expected, so POPs remain around 40 percent the rest of
the afternoon, but anyone under one of these storms could be
dealing with damaging winds, torrential rainfall and frequent
lightning. Flooding threat is pretty minimal at this point, as
storms have been moving very quickly thus far. Again, if
anything gets hung up and the intersection of boundaries, you
could see some isolated issues if it is over a sensitive area,
but that should be few and far between.

Convection wanes a bit Sunday given quasi-zonal flow aloft and
the strengthening upper-level ridge axis nearby. A few storms
may develop over the higher elevations, but coverage will be
much less than in recent days. This will be short-lived however,
with storm chances increasing once again Tuesday through the
end of the week as a series of shortwave disturbances pass
through.

Things have changed slightly on Monday, as precipitation
chances have increased a bit over the past several model runs.
Another piece of shortwave energy will slide across the region
amidst a hot and very humid airmass yet again. Similar to what
we are seeing today, coverage is a question mark at this point,
but could be a couple of pretty strong to severe storms that
day. Something that bears watching at this stage, but confidence
is just too low for a severe weather outlook at this point.

Outside of he storm chances expect highs in the upper 80s and low
90s with heat indices east of the Blue Ridge up around 100 degrees.
The hottest days look to be Monday and Tuesday given the
strengthened subtropical ridge over the region. Highs will push into
the mid 90s with heat indices closer to 105 degrees east of the Blue
Ridge/along the urban corridor.


KEY MESSAGE 2...A cold front could arrive late next week bringing
relief from the heat and humidity into the upcoming weekend.

Daily storm chances look to continue through at least Friday as a
more potent frontal system tracks toward the region. Ahead of that
front will be several fast moving shortwave disturbances which will
help aid in shower and thunderstorm development during the diurnal
period. Storm coverage is a bit uncertain with activity remaining
isolated to scattered Tuesday becoming a scattered to numerous
Wednesday into late week as the front tries to push through.
Speaking of the front, details remain a bit murky on it`s passage.
Most 00z ensemble/deterministic guidance suggests a frontal passage
Thursday afternoon into Saturday. Guidance also depicts an MCS type
setup during the Tuesday and Wednesday timeframe. Machine learning
guidance is grabbing onto this as well with probabilities running
between 15 to 30 percent for severe weather during the midweek
timeframe. SPC mentions areas back toward our west on the Day 4 and
5 outlook, so something we`ll continue to monitor, especially as the
subtropical ridge flattens.

There is a bit more uncertainty in regards to severe weather
Thursday through Saturday. Of course with any decent frontal passage
will have to be monitor given machine probabilities remaining
between 5-30 percent for severe weather. This will ultimately be
determined by the timing of the front in regards to the peak heating
period. Temperatures will cool from the 90s into the 80s late week.
Weather does look to improve for the upcoming weekend as Canadian
high pressure works into the region.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Prevailing VFR conditions are expected across the terminals through
the middle of next week given subtropical high pressure offshore and
the lack of any real front passing through. Brief periods of sub-VFR
are likely during the afternoon and evening hours due to
thunderstorms.

For the rest of the afternoon, maintaining PROB30s for now, as
redevelopment of storms thus far after the initial wave has been
very sporadic. Still think any of the terminals could see a
storm this afternoon, but not certain enough to put an FM or
TEMPO in at this time. Outflows from the stuff that slid across
the MD/PA border this morning are through all but CHO, so CHO
probably stands the best chance. However, there is some
redevelopment just south of CHO, so there is some chance that
could happen anywhere. BWI and MTN really got worked over with
the initial line, so perhaps those areas have slightly less of a
chance than the rest.

Storm coverage drops off even more Sunday with high pressure
briefly returning. By Monday though, chances have increased
again, primarily for the northern terminals. Still only around a
30 percent chance at this time, but any storms Monday could
bring gusty winds and lightning once again. Outside of the
thunderstorms expect patchy fog between the terminals each
morning through early next week. Winds will remain light out of
the west and southwest at less than 15 kts.

Temporary restrictions will continue at times through at least
Friday as we await a cold front to sweep through.

&&

.MARINE...
Small Craft Advisories are in effect for portions of the open
water due to southerly channeling mainly later this afternoon
and evening. Daily shower and thunderstorm chances are expected
each afternoon and evening through early next week, except for
on Sunday. Special Marine Warnings may be needed to encompass
any any stronger thunderstorms that may form. Damaging wind
gusts and frequent cloud-to-ground lightning will be the main
threats between 19z-01z/ 3-9pm each day.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ534-537-
     543.

&&

$$

DISCUSSION...CJL/EST
AVIATION...CJL/EST
MARINE...CJL/EST

NWS LWX Office Area Forecast Discussion